tag:theconversation.com,2011:/global/topics/east-australian-current-10839/articlesEast Australian Current – The Conversation2023-10-06T04:19:38Ztag:theconversation.com,2011:article/2149622023-10-06T04:19:38Z2023-10-06T04:19:38ZClimate change is disrupting ocean currents. We’re using satellites and ships to understand how<figure><img src="https://images.theconversation.com/files/552445/original/file-20231006-27-b8rch3.jpeg?ixlib=rb-1.1.0&rect=51%2C0%2C6809%2C3939&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia25595-swot-in-orbit-illustration">CNES</a></span></figcaption></figure><p>Earth’s ocean is incredibly vast. Some parts of it are <a href="https://www.theguardian.com/environment/shortcuts/2018/may/18/point-nemo-is-the-most-remote-oceanic-spot-yet-its-still-awash-with-plastic">so remote</a> that the nearest human habitation is the International Space Station.</p>
<p>As the world warms, what happens in the ocean – and what happens <em>to</em> the ocean – will be vital to all our lives. But to monitor what’s happening in remote waters, we need to study the ocean from space.</p>
<p>Late last year, NASA and CNES, the French space agency, launched a satellite that promises to give scientists a far better view than ever before of the ocean’s surface. The <a href="https://swot.jpl.nasa.gov/">Surface Water and Ocean Topography (SWOT)</a> mission will reveal ocean currents that play a crucial role in the weather and climate.</p>
<p>To make the most of the satellite observations, we need to compare them with measurements made at surface level. That is why we are heading out to sea on the state-of-the-art CSIRO research vessel <a href="https://mnf.csiro.au/en/RV-Investigator">RV Investigator</a> to gather essential ocean data under the satellite’s path as it orbits Earth. </p>
<h2>Current affairs</h2>
<p>Climate change is disrupting the global network of currents that connect the oceans. Researchers have <a href="https://theconversation.com/torrents-of-antarctic-meltwater-are-slowing-the-currents-that-drive-our-vital-ocean-overturning-and-threaten-its-collapse-202108">detected a slowdown</a> of the deep “overturning circulation” that carries carbon, heat, oxygen and nutrients from Antarctica around the globe. Meanwhile, at the surface, ocean currents are <a href="https://theconversation.com/satellites-reveal-ocean-currents-are-getting-stronger-with-potentially-significant-implications-for-climate-change-159461">becoming more energetic</a>. </p>
<p>We have also seen dramatic changes in fast, narrow rivers of seawater called <a href="https://theconversation.com/shifting-ocean-currents-are-pushing-more-and-more-heat-into-the-southern-hemispheres-cooler-waters-189122">western boundary currents</a>, such as the <a href="https://oceanservice.noaa.gov/facts/gulfstreamspeed.html#:%7E:text=The%20Gulf%20Stream%20is%20an,flowing%20northeast%20across%20the%20Atlantic">Gulf Stream</a> and the <a href="https://theconversation.com/can-you-surf-the-east-australian-current-finding-nemo-style-27392">East Australian Current</a>. </p>
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Read more:
<a href="https://theconversation.com/shifting-ocean-currents-are-pushing-more-and-more-heat-into-the-southern-hemispheres-cooler-waters-189122">Shifting ocean currents are pushing more and more heat into the Southern Hemisphere’s cooler waters</a>
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<p>These currents funnel heat from the tropics towards the poles, and in recent decades they have become hotspots for ocean warming. In the Southern Hemisphere, they are <a href="https://www.nature.com/articles/nclimate1353">warming two to three times faster</a> than the global average.</p>
<p>As these currents destabilise, they <a href="https://www.nature.com/articles/nclimate1353">alter how heat is distributed</a> throughout the ocean. This in turn will cause major changes in local weather and marine ecosystems that may impact the lives of millions of people. </p>
<h2>Playground physics</h2>
<p>The SWOT satellite mission will give researchers a powerful new tool to monitor changes in ocean currents by using accurate satellite measurements of the sea surface – plus a little bit of playground physics. </p>
<p>The satellite carries an instrument that will map variations in the height of the sea surface in unprecedented detail. These variations might be less than a metre in height over horizontal distances of hundreds of kilometres. But oceanographers can use the measurements to estimate ocean currents flowing underneath. </p>
<p>Small variations in the height of the sea surface create horizontal pressure differences that try to push water away from areas of high sea level and towards areas of low sea level. That pressure difference is balanced by the Coriolis force, which gently deflects ocean currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. </p>
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<a href="https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C1270%2C718&q=45&auto=format&w=1000&fit=clip"><img alt="Illlustration showing Earth from space with the ocean filled with complex whorls of current" src="https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C1270%2C718&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552426/original/file-20231005-17-76igp5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Earth’s oceans are filled with complex network of currents driven by the rotation of the planet.</span>
<span class="attribution"><span class="source">NASA / Goddard Space Flight Center Scientific Visualization Studio</span></span>
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<p>You can experience the Coriolis force at the playground. Step onto a merry-go-round and ask a friend to stand on the opposite side from you. As you start spinning, toss a ball to your friend. You will notice that the ball appears to be <a href="https://www.youtube.com/watch?v=mPsLanVS1Q8&ab_channel=NationalGeographic">deflected away</a> from the direction of rotation. </p>
<p>In reality, the ball has moved in a straight line; your friend has simply moved away from where you were aiming. But, to you both, the ball seems to have been deflected by an invisible “pseudo-force” – the Coriolis force. </p>
<p>Now imagine the merry-go-round is Earth, and the ball is an ocean current. The Coriolis deflection is enough to balance pressure differences across hundreds of kilometres and causes seawater to flow in ocean currents. </p>
<h2>Science at sea</h2>
<p>By carefully measuring the height of the sea surface and using our knowledge of the Coriolis force, oceanographers will be able to use data from NASA’s satellite to reveal ocean currents in greater detail than ever before. But to make sense of that data, researchers need to compare satellite measurements with observations made down here on Earth. </p>
<p>That’s why we are <a href="https://www.smh.com.au/national/nsw/underwater-cyclones-off-sydney-are-giant-floating-laboratory-s-next-mission-20231005-p5ea0q.html">leading a voyage</a> of more than 60 scientists, support staff and crew aboard the <a href="https://mnf.csiro.au/en/RV-Investigator">RV Investigator</a>, Australia’s national flagship for blue water ocean research.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of a blue-and-white ship, the RV Investigator, sailing through the sea beneath grey skies." src="https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552440/original/file-20231006-19-o6ad33.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A 24-day voyage aboard the RV Investigator will gather data about oceans currents.</span>
<span class="attribution"><span class="source">CSIRO</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>Our 24-day voyage will study ocean dynamics off Australia’s southeast coast using the Investigator’s world-class scientific equipment, including satellite-tracked floating buoys and drifters that will be used to measure the real-time movement of currents at the ocean surface. </p>
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Read more:
<a href="https://theconversation.com/explainer-the-rv-investigators-role-in-marine-science-35239">Explainer: the RV Investigator’s role in marine science</a>
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<p>The voyage is part of a <a href="https://www.swot-adac.org/">huge collaboration</a> by scientists around the world to gather observational data under the satellite’s path as it orbits Earth. This data will help validate satellite measurements and improve weather forecasts, including those from Australia’s Bureau of Meteorology, and assist with climate risk assessment and prediction.</p>
<p>We hope to better understand how our oceans are changing using what we observe in space, at sea — and in the playground. </p>
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<p><em>This research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.</em></p>
<p><em>You can follow our voyage on <a href="https://twitter.com/hashtag/RVInvestigator?src=hashtag_click">Twitter/X</a> using the hashtag</em> #RVInvestigator.</p><img src="https://counter.theconversation.com/content/214962/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shane Keating receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Moninya Roughan receives funding from Australian Research Council, Australia's Marine National Facility, and the National Collaborative Research Infrastructure Scheme</span></em></p>A sea voyage and a satellite mission will combine to produce a more detailed picture of the ocean’s currents than ever before.Shane Keating, Senior Lecturer in Mathematics and Oceanography, UNSW SydneyMoninya Roughan, Professor in Oceanography, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2119022023-09-04T20:06:03Z2023-09-04T20:06:03ZMarine heatwaves don’t just hit coral reefs. They can cause chaos on the seafloor<figure><img src="https://images.theconversation.com/files/545458/original/file-20230830-15-tabdkd.jpg?ixlib=rb-1.1.0&rect=0%2C407%2C3888%2C2479&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Most of us know what a heatwave feels like on land – sweltering heat for days. But oceans get heatwaves too. When water temperature goes over a seasonal threshold for five days or more, that’s a marine heatwave. They do their worst damage in summer, when the ocean is already at its warmest, but they can occur any time of year. </p>
<p>Over 90% of the heat trapped by greenhouse gases has <a href="https://climate.nasa.gov/vital-signs/ocean-warming/#:%7E:text=Covering%20more%20than%2070%25%20of,heat%20as%20Earth's%20entire%20atmosphere.">gone into</a> our oceans. So it’s no surprise marine heatwaves are getting much more intense and more frequent. This year has been off the charts. From April this year, the world’s average ocean temperature <a href="https://climatereanalyzer.org/clim/sst_daily/">has been</a> the highest ever recorded. </p>
<p>Since the 1980s, satellites have revolutionised ocean science by making it possible to take daily measurements of ocean temperatures. But satellites watch from above. They can’t see what’s happening below the surface. </p>
<p>Our <a href="https://doi.org/10.1038/s43247-023-00966-4">new research</a> explores what’s happening in deeper waters. It turns out, marine heatwaves aren’t just on the surface. In the most devastating marine heatwaves, heat can penetrate right down to the sea bed. Remarkably, some heatwaves only affect the seafloor. </p>
<h2>Why do deep marine heatwaves matter?</h2>
<p>While we usually only see sea creatures at the surface of the ocean, there’s life all the way down. In the shallower seafloors of the continental shelf – the sunken parts of our continents – live fish, kelp beds, sponges, cold water corals, shellfish and crustaceans. </p>
<p>These shallow oceans are, on average, less than 100 metres deep. When the shelf ends, there’s usually an abrupt slope into the deep ocean, where there are kilometres of water between surface and seabed. </p>
<p>Marine heatwaves are damaging to life in the seas covering the continental shelf. Creatures here are sensitive to extreme temperatures, just like those at the surface. But “extreme” to them is different to what we think of as extreme. If you’re used to water at 12°C, a heatwave of 15°C can be devastating. </p>
<p>When marine heatwaves strike, they can kill. More than a billion sea creatures died during a <a href="https://www.nature.com/articles/s41467-023-36289-3">single heatwave</a> off the coast of the western United States and Canada in 2021. This year, extreme heatwaves have hit large parts of the oceans during the northern summer. </p>
<p>Fish and other creatures that can move do so, heading towards the poles or down deeper in search of cooler water. Those that can’t have to endure it or die. Heatwaves can trigger migration. New species arrive, seeking refuge and can alter the ecosystem. </p>
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Read more:
<a href="https://theconversation.com/an-extreme-heatwave-has-hit-the-seas-around-the-uk-and-ireland-heres-whats-going-on-208052">An 'extreme' heatwave has hit the seas around the UK and Ireland – here's what's going on</a>
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<h2>We don’t know much about deeper marine heatwaves</h2>
<p>The seas covering the continental shelf are relatively shallow compared to the kilometres of water in the deep oceans. But even so, it’s impossible to see what’s going on below using satellites or <a href="https://imos.org.au/facilities/oceanradar">high-frequency radar</a>. </p>
<p>The sea is a hostile environment. Instruments are subject to high pressure, corrosive salt water and marine organisms like oysters and sponges settling on them. This is one reason why we only have very limited data on long-term trends in temperatures under the surface. But these records are vital to calculate typical temperatures for the time of year and to figure out what constitutes an extreme. </p>
<p>Australia is one of the few places generating this kind of valuable data long-term. Off the coast of the southeast lie many oceanographic moorings – a floating <a href="https://imos.org.au/facilities/nationalmooringnetwork/">collection of sensors</a> anchored to the bottom. One of these has been measuring daily temperatures from the surface to the seafloor 65 metres down since 1993. </p>
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<a href="https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="oceanographic instrument" src="https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=853&fit=crop&dpr=1 600w, https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=853&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=853&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1072&fit=crop&dpr=1 754w, https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1072&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/545276/original/file-20230829-19-lqlw60.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1072&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">In addition to coastal moorings, this oceanographic instrument also measures temperature and salinity of the ocean.</span>
<span class="attribution"><span class="source">Amandine Schaeffer</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Our earlier research found marine heatwaves at depth can actually be <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL073714">more intense</a> and <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094785">last longer</a> compared to the surface. But why? </p>
<p>In our new research, we looked at the temperature data closely. We found marine heatwaves come in a variety of types and have different causes. We also found some types of marine heatwave are more likely during particular seasons. </p>
<p>For instance, winter marine heatwaves often run from surface to seafloor. They occur when the powerful, deep and warm East Australian Current snakes westward towards the coast. As the current swings over the continental slope, it drags warm water over the shelf and close to the coast. </p>
<p>In summer, Australia gets two very different types of heatwave in our oceans. The first occur when we get blue-sky weather. With few clouds, more heat from the sun gets into the oceans. They can also occur when there are weaker winds and less ocean cooling from evaporation. These heatwaves are confined to the surface and a few metres below. </p>
<p>Then there’s the second, a very weird heatwave system that only appears close to the seafloor. These are produced when strong wind creates currents driving warm, shallower water down to the bottom. On the east coast, these currents come from cold winds from the south. So even while you’re shivering through cold winds from the Southern Ocean, the ocean seafloor may be sweltering through a heatwave. These may be the most destructive to ecosystems but go all but unnoticed. </p>
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<span class="caption">This figure shows the different types of marine heatwaves affecting coastal waters (shown by the anomalous heat in red)</span>
<span class="attribution"><span class="source">Author provided</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<h2>Marine heatwaves are not created equally</h2>
<p>Our research has shown marine heatwaves come in different flavours. That matters, because it will allow us to get better at predicting if a heatwave is about to strike our oceans. And it will let us anticipate which parts of the water column are about to be hit, and which ecosystems. </p>
<p>Of course, slowing ocean warming and preventing marine heatwaves from damaging ecosystems means slashing carbon emissions. But while we work on that, this knowledge could give us time to find strategies to reduce the undersea death toll – and the damage to tourism and fishing which rely on these ecosystems surviving. </p>
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Read more:
<a href="https://theconversation.com/coral-reefs-how-climate-change-threatens-the-hidden-diversity-of-marine-ecosystems-211007">Coral reefs: How climate change threatens the hidden diversity of marine ecosystems</a>
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<img src="https://counter.theconversation.com/content/211902/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amandine Schaeffer receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Alex Sen Gupta receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Moninya Roughan receives funding from the Australian Research Council, and Australia’s Integrated Marine Observing System (IMOS) – IMOS is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS).</span></em></p>Marine heatwaves aren’t just on the surface. They can be at their most destructive when they sweep along the seafloor.Amandine Schaeffer, Senior lecturer, UNSW SydneyAlex Sen Gupta, Senior Lecturer, School of Biological, Earth and Environmental Sciences, UNSW SydneyMoninya Roughan, Professor in Oceanography, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1892312022-08-28T20:04:50Z2022-08-28T20:04:50ZThousands of photos captured by everyday Australians reveal the secrets of our marine life as oceans warm<figure><img src="https://images.theconversation.com/files/481238/original/file-20220826-8211-tauikk.jpg?ixlib=rb-1.1.0&rect=160%2C5%2C1459%2C818&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.redmap.org.au/sightings/3798/">Redmap/Jacob Bradbury</a></span></figcaption></figure><p>As the planet heats up, many marine plants and animals are <a href="https://theconversation.com/climate-driven-species-on-the-move-are-changing-almost-everything-74752">moving</a> locations to keep pace with their preferred temperatures. In the Southern Hemisphere, this means species are setting up home further south.</p>
<p>This shift alters what we see when we go snorkelling, and when and where we catch our seafood. Crucially, it also changes sensitive marine ecosystems. </p>
<p>But it’s not always easy for scientists to know exactly what’s happening below the ocean’s surface. To help tackle this, we examined tens of thousands of photographs taken by Australian fishers and divers submitted to citizen science programs over the last decade. </p>
<p>They revealed climate change is already disrupting the structure and function of our marine ecosystems – sometimes in ways previously unknown to marine scientists.</p>
<figure class="align-center ">
<img alt="man holds large silver fish" src="https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1914%2C1074&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/481235/original/file-20220826-18-8j5rl4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The authors examined tens of thousands of photographs taken by Australian fishers and divers, such as this image of a bonefish found off Western Australia.</span>
<span class="attribution"><span class="source">Redmap</span></span>
</figcaption>
</figure>
<h2>Species on the move</h2>
<p>Warming over the Pacific Ocean has strengthened the East Australian Current over the past several decades, as the below-right animation shows. This has caused waters off Southeast Australia to warm at almost <a href="https://link.springer.com/article/10.1007/s11160-013-9326-6">four times</a> the global average. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Animated map of sea surface temperatures in southeast Australia from 2004 to 2022" src="https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480969/original/file-20220824-14-i52yob.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Animated map of sea surface temperatures in southeast Australia from 2004 to 2022. Data sourced from NASA.</span>
<span class="attribution"><span class="source">Barrett Wolfe</span></span>
</figcaption>
</figure>
<p>There is already irrefutable evidence <a href="https://www.science.org/doi/10.1126/science.aai9214">climate change</a> is causing marine species <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15634">to move</a>. Understanding this phenomenon is crucial for conservation, fisheries management and human health. </p>
<p>For example, if fish susceptible to carrying <a href="https://www.redmap.org.au/news/2020/12/10/ciguatera-fish-poisoning/">toxins</a> start turning up where you go fishing, you’d want to know. And if an endangered species moves somewhere new, we need to know so we can protect it.</p>
<p>But the <a href="https://www.ga.gov.au/scientific-topics/marine/coasts-estuaries#:%7E:text=The%20Australian%20coastline%20extends%20approximately,includes%20more%20than%201000%20estuaries.">sheer scale</a> of the Australian coastline means scientists can’t monitor changes in all areas. That’s where the public can help. </p>
<p>Fishers, snorkelers and divers often routinely visit the same place over time. Many develop strong knowledge of species found in a given area. </p>
<p>When a new or unusual species appears in their patch, these members of the public can excel at detecting it. So our project set out to tap into this invaluable community knowledge.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-driven-species-on-the-move-are-changing-almost-everything-74752">Climate-driven species on the move are changing (almost) everything</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="large fish and smaller fish on blue marine background" src="https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/481221/original/file-20220826-8211-tw4ry1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This sighting of a sea sweep – recorded in May this year off Kangaroo Island by a member of the public – may indicate the species is extending its range.</span>
<span class="attribution"><span class="source">Redmap/Daniel Easton</span></span>
</figcaption>
</figure>
<h2>The value of citizen science</h2>
<p>The <a href="https://www.redmap.org.au/">Redmap</a> citizen science project began in Tasmania in 2009 and went national in 2012. It invites the public to share sightings of marine species uncommon in their area. </p>
<p>Redmap stands for Range Extension Database and Mapping project. Redmap members use their local knowledge to help monitor Australia’s vast coastline. When something unusual for a given location is spotted, fishers and divers can upload a photo with location and size information. </p>
<p>The photos are then verified by a <a href="https://www.redmap.org.au/about/meet-the-scientists/">network</a> of almost 100 marine scientists around Australia. Single observations cannot tell us much. But over time, the data can be used to map which species may be extending their range further south.</p>
<p>The project is supported by the University of Tasmania’s <a href="https://www.imas.utas.edu.au/">Institute for Marine and Antarctic Studies</a>, together with other Australian universities and a range of Commonwealth and state-government bodies.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/warming-oceans-are-changing-australias-fishing-industry-98301">Warming oceans are changing Australia's fishing industry</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=488&fit=crop&dpr=1 754w, https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=488&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/481220/original/file-20220826-12-dh55qg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=488&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Screenshot of the Redmap website highlighting a recent coral sighting.</span>
<span class="attribution"><span class="source">Redmap</span></span>
</figcaption>
</figure>
<p>We also examined data from two other national marine citizen science programs: <a href="https://reeflifesurvey.com/">Reef Life Survey</a> and <a href="https://www.inaturalist.org/projects/australasian-fishes">iNaturalist Australasian Fishes Project</a>. The resulting dataset encompassed ten years of photographed species observations made by almost 500 fishers, divers, snorkelers, spearfishers and beachcombers.</p>
<p>The citizen scientists recorded 77 species further south than where they lived a decade ago. Many were observed at their new location over multiple years and even in cooler months. </p>
<p>For example, spearfisher Derrick Cruz got a surprise in 2015 when he saw a coral trout swimming through a temperate kelp forest in his local waters off Sydney, much further south than he’d seen before. He submitted the below photo to Redmap, which was then verified by a scientist.</p>
<figure class="align-center ">
<img alt="Man snorkeling in the ocean, holding up a large orange fish" src="https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480719/original/file-20220824-22-qpj3ls.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Spearfisher Derrick Cruz, pictured with a coral trout off Sydney.</span>
<span class="attribution"><span class="source">Redmap</span></span>
</figcaption>
</figure>
<p>Citizen scientists using Redmap were also the first to spot the <a href="https://www.redmap.org.au/sightings/566/">gloomy octopus</a> off Tasmania in 2012. Subsequent <a href="https://www.abc.net.au/news/2018-06-28/gloomy-octopus-migrating-to-tasmania-due-to-climate-warming/9919122">genetic studies</a> confirmed the species’ rapid extension into Tasmanian waters. </p>
<p>Similarly, solo eastern rock lobsters have been turning up in Tasmania for some time. But Redmap <a href="https://www.redmap.org.au/sightings/522/">sightings</a> recorded dozens of individuals living together in a “den”, which had not been observed previously.</p>
<p>Other species recorded by citizen scientists moving south include the <a href="https://www.redmap.org.au/sightings/3465/">spine-cheek clownfish</a>, Moorish idol and <a href="https://www.redmap.org.au/sightings/4248/">tiger sharks</a>.</p>
<h2>Supporting healthy oceans</h2>
<p>Using the citizen science data, we produced a <a href="https://www.redmap.org.au/media/uploads/2022/08/08/redmap-report-card-project-nesp-report-draft.pdf">report</a> outlining the assessment methods underpinning our study. We’ve also produced detailed state-based report cards for Western Australia, Tasmania and New South Wales, where coastal waters are warming much faster than the global average.</p>
<p>We also generated a map of the species shifts this revealed, and a downloadable <a href="https://www.redmap.org.au/article/report-card/">poster</a> summarising the findings. This allows the public – including those who contributed data – to see at a glance how climate change is affecting our oceans. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map of Australia with southerly lines around the coastline depicting how species distributions have shifted over the last decade" src="https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=459&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=459&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=459&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=576&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=576&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480858/original/file-20220824-14-p217nk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=576&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left, a downloadable poster summarising the species shifts in distribution. Right, the state-based report cards.</span>
</figcaption>
</figure>
<p>Citizen science has benefits beyond helping us understand changes in natural systems. Projects such as Redmap open up a community conversation about the impacts of climate change in Australia’s marine environment - using the public’s own knowledge and photos.</p>
<p>Our research <a href="https://www.sciencedirect.com/science/article/pii/S0964569117305665">suggests</a> this method engages the community and helps get people involved in documenting and understanding the problems facing our oceans and coasts. </p>
<p>A better understanding – by both scientists and the public – will help ensure healthy ecosystems, strong conservation and thriving fisheries in future. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-you-can-help-scientists-track-how-marine-life-reacts-to-climate-change-33370">How you can help scientists track how marine life reacts to climate change</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/189231/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gretta Pecl receives funding from the Australian Research Council (ARC), the Fisheries Research & Development Corporation (FRDC), the Department of Agriculture Water and the Environment through the National Environmental Science Program (NESP), and the Department of Primary Industries NSW. She is also a Lead Author on the recent IPCC assessment report, and received funding from the Department of Environment and Energy to support travel to IPCC meetings. </span></em></p><p class="fine-print"><em><span>Barrett Wolfe receives funding from the Fisheries Research and Development Corporation, the Department of Agriculture Water and the Environment through the National Environmental Science Program, Department of Primary Industries NSW and NRE Tasmania. He has received past research funding from Seaworld Research and Rescue Foundation and PADI Foundation.</span></em></p><p class="fine-print"><em><span>Curtis Champion receives funding from the Fisheries Research and Development Corporation. He works for the NSW Department of Primary Industries.</span></em></p><p class="fine-print"><em><span>Jan Strugnell receives funding from the Australian Research Council (ARC), the Fisheries Research and Development Corporation (FRDC), the Department of Agriculture Water and the Environment through the National Environmental Science Program (NESP) and the Queensland Government through the Queensland Citizen Science Grants.</span></em></p><p class="fine-print"><em><span>Sue-Ann Watson receives funding from the Australian Research Council (ARC), the Department of Agriculture Water and the Environment through the National Environmental Science Program (NESP) and Queensland Government through the Queensland Citizen Science Grants. </span></em></p>The photographs show how climate change is disrupting our marine ecosystems – sometimes in ways previously unknown to marine scientists.Gretta Pecl, Professor, ARC Future Fellow & Director of the Centre for Marine Socioecology, University of TasmaniaBarrett Wolfe, Postdoctoral Research Fellow, University of TasmaniaCurtis Champion, Research Scientist, Southern Cross UniversityJan Strugnell, Professor Marine Biology and Aquaculture, James Cook UniversitySue-Ann Watson, Senior Research Fellow, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1653962021-08-09T08:00:51Z2021-08-09T08:00:51ZClimate change has already hit Australia. Unless we act now, a hotter, drier and more dangerous future awaits, IPCC warns<p>Australia is experiencing widespread, rapid climate change not seen for thousands of years and may warm by 4°C or more this century, according to a highly anticipated <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">report</a> by the Intergovernmental Panel on Climate Change (IPCC).</p>
<p>The assessment, released on Monday, also warns of unprecedented increases in climate extremes such as bushfires, floods and drought. But it says deep, rapid emissions cuts could spare Australia, and the world, from the most severe warming and associated harms.</p>
<p>The report is the sixth produced by the IPCC since it was founded in 1988 and provides more regional information than any previous version. This gives us a clearer picture of how climate change will play out in Australia specifically. </p>
<p>It confirms the effects of human-caused climate change have well and truly arrived in Australia. This includes in the region of the East Australia Current, where the ocean is warming at a rate more than four times the global average.</p>
<p>We are climate scientists with expertise across historical climate change, climate projections, climate impacts and the carbon budget. We have been part of the international effort to produce the IPCC report over the past three years.</p>
<p>The report finds even under a moderate emissions scenario, the global effects of climate change will worsen significantly over the coming years and decades. Every fraction of a degree of global warming increases the likelihood and severity of many extremes. That means every effort to reduce greenhouse gas emissions matters.</p>
<h2>Australia is, without question, warming</h2>
<p>Australia has warmed by about 1.4°C since 1910. The IPCC assessment concludes the extent of warming in both Australia and globally are impossible to explain without accounting for the extra greenhouse gases in the atmosphere from human activities. </p>
<p>The report introduces the concept of Climate Impact-Drivers (CIDs): 30 climate averages, extremes and events that create climate impacts. These include heat, cold, drought and flood. </p>
<p>The report confirms global warming is driving a significant increase in the intensity and frequency of extremely hot temperatures in Australia, as well as a decrease in almost all cold extremes. The IPCC noted with high confidence that recent extreme heat events in Australia were made more likely or more severe due to human influence. </p>
<p>These events include:</p>
<ul>
<li><p>the Australian summer of 2012–13, also known as the Angry Summer, when <a href="https://theconversation.com/angry-summer-shaped-by-a-shifting-climate-12580">more than 70%</a> of Australia experienced extreme temperatures</p></li>
<li><p>the <a href="https://www.abc.net.au/news/2014-11-14/g20-leaders-swelter-as-brisbane-residents-head-to-the-beach/5891494">Brisbane heatwave</a> in 2014</p></li>
<li><p>extreme heat preceding the <a href="https://www.abc.net.au/news/2018-11-28/queensland-bushfire-emergency-as-thousands-evacuated/10563834">2018 Queensland fires</a></p></li>
<li><p>the heat leading into the Black Summer bushfires of 2019-20.</p></li>
</ul>
<p>The IPCC report notes very high confidence in further warming and heat extremes through the 21st century – the extent of which depends on global efforts to reduce greenhouse gas emissions.</p>
<p>If global average warming is limited to 1.5°C this century, Australia would warm to between 1.4°C to 1.8°C. If global average warming reaches 4°C this century, Australia would warm to between 3.9°C and 4.8°C . </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=634&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=634&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=634&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=797&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=797&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415156/original/file-20210809-17-1lz4fv6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=797&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">IPCC</span></span>
</figcaption>
</figure>
<p>The IPCC says as the planet warms, future heatwaves in Australia – and globally – will be hotter and last longer. Conversely, cold extremes will be both less intense and frequent.</p>
<p>Hotter temperatures, combined with reduced rainfall, will make parts of Australia more arid. A drying climate can lead to reduced river flows, drier soils, mass tree deaths, crop damage, bushfires and drought.</p>
<p>The southwest of Western Australia remains a globally notable hotspot for <a href="https://theconversation.com/saving-water-in-a-drying-climate-lessons-from-south-west-australia-28517">drying</a> attributable to human influence. The IPCC says this drying is projected to continue as emissions rise and the climate warms. In southern and eastern Australia, drying in winter and spring is also likely to continue. This phenomenon is depicted in the graphic below.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=757&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=757&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415134/original/file-20210809-25-zca704.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=757&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">IPCC</span></span>
</figcaption>
</figure>
<h2>Climate extremes on the rise</h2>
<p>Heat and drying are not the only climate extremes set to hit Australia in the coming decades. The report also notes:</p>
<ul>
<li><p>observed and projected increases in Australia’s dangerous fire weather</p></li>
<li><p>a projected increase in heavy and extreme rainfall in most places in Australia, particularly in the north</p></li>
<li><p>a projected increase in river flood risk almost everywhere in Australia.</p></li>
</ul>
<p>Under a warmer climate, extreme rainfall in a single hour or day can become more intense or more frequent, even in areas where the average rainfall declines.</p>
<p>For the first time, the IPCC report provides regional projections of coastal hazards due to sea level rise, changing coastal storms and coastal erosion – changes highly relevant to beach-loving Australia. </p>
<p>This century, for example, sandy shorelines in places such as eastern Australia are projected to retreat by more than 100 metres, under moderate or high emissions pathways. </p>
<figure class="align-center ">
<img alt="homes on sand" src="https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=520&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=520&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414743/original/file-20210805-25-f9t4ay.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=520&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Some sandy shorelines may retreat by more than 100 metres.</span>
<span class="attribution"><span class="source">James Gourley/AAP</span></span>
</figcaption>
</figure>
<h2>Hotter, more acidic oceans</h2>
<p>The IPCC report says globally, climate change means oceans are becoming more acidic and losing oxygen. Ocean currents are becoming more variable and salinity patterns – the parts of the ocean that are saltiest and less salty – are changing. </p>
<p>It also means sea levels are rising and the oceans are becoming warmer. This is leading to an increase in marine heatwaves such as those which have contributed to mass coral bleaching on the Great Barrier Reef in recent decades.</p>
<p>Notably, the region of the East Australia Current which runs south along the continent’s east coast is warming at a rate more than four times the global average. </p>
<p>The phenomenon is playing out in all regions with so-called “western boundary currents” – fast, narrow ocean currents found in all major ocean gyres. This pronounced warming is affecting marine ecosystems and aquaculture and is projected to continue.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-just-spent-two-weeks-surveying-the-great-barrier-reef-what-we-saw-was-an-utter-tragedy-135197">We just spent two weeks surveying the Great Barrier Reef. What we saw was an utter tragedy</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="bleached coral with diver" src="https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414740/original/file-20210805-17-12jvgnv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The region of the East Australia Current, which includes the Great Barrier Reef, is warming at a rate more than four times the global average.</span>
<span class="attribution"><span class="source">XL Catlin Seaview Survey</span></span>
</figcaption>
</figure>
<h2>Where to from here?</h2>
<p>Like all regions of the world, Australia is already feeling the effects of a changing climate. </p>
<p>The IPCC confirms there is no going back from some changes in the climate system. However, the consequences can be slowed, and some effects stopped, through strong, rapid and sustained reductions in global greenhouse gas emissions. </p>
<p>And now is the time to start adapting to climate change at a large scale, through serious planning and on-ground action. </p>
<p>To find out more about how climate change will affect Australia, the latest IPCC report includes an <a href="https://interactive-atlas.ipcc.ch">Interactive Atlas</a>. Use it to explore past trends and future projections for different emissions scenarios, and for the world at different levels of global warming.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CSWJ-p2hXyu/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">This is the most sobering report card yet on climate change and Earth's future. Here’s what you need to know</a>
</strong>
</em>
</p>
<hr>
<p><em><a href="https://theconversation.com/au/topics/ipcc-report-2021-108383">Click here</a> to read more of The Conversation’s coverage of the IPCC report</em></p><img src="https://counter.theconversation.com/content/165396/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Grose receives funding from the Australian National Environmental Science Program - Earth Systems and Climate Change Hub</span></em></p><p class="fine-print"><em><span>Dr Joelle Gergis has received funding from the Australian Research Council in the past. She currently receives funding from the Australian National University. The Australian Government's Department of Industry, Science, Energy and Resources provided travel funding to support her participation in the IPCC Sixth Assessment Report.</span></em></p><p class="fine-print"><em><span>Pep Canadell receives funding from the Australian National Environmental Science Program - Earth Systems and Climate Change Hub</span></em></p><p class="fine-print"><em><span>Roshanka Ranasinghe is employed at IHE Delft Institute for Water Education/Deltares, Delft, The Netherlands</span></em></p>Australia may warm by 4°C or more this century, the IPCC has found. As these IPCC authors explain, there is no going back from some changes in the climate system.Michael Grose, Climate projections scientist, CSIROJoelle Gergis, Senior Lecturer in Climate Science, Australian National UniversityPep Canadell, Chief research scientist, Climate Science Centre, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRORoshanka Ranasinghe, Professor of Climate Change impacts and Coastal RiskLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1582192021-04-05T20:06:37Z2021-04-05T20:06:37ZDoritos, duckies and disembodied feet: how tragedy and luck reveals the ocean’s hidden highways<figure><img src="https://images.theconversation.com/files/393017/original/file-20210401-13-6dmhz.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6016%2C3971&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The grisly <a href="https://www.smh.com.au/national/nsw/two-men-walking-on-south-coast-beach-make-grisly-find-of-remains-in-shoe-belonging-to-melissa-caddick-20210226-p57653.html">discovery</a> in February of a disembodied foot on a New South Wales beach was a tragic twist in the mystery of missing Sydney woman Melissa Caddick.</p>
<p>DNA testing has shown the remains belong to Caddick, who vanished from her Dover Heights home in November 2020 after allegedly <a href="https://www.smh.com.au/national/nsw/more-than-20m-of-investor-funds-deposited-into-melissa-s-account-court-20201214-p56nfc.html">stealing more than A$25 million</a> from investors. Corporate regulator ASIC last week <a href="https://www.smh.com.au/national/nsw/criminal-charges-against-melissa-caddick-to-be-withdrawn-20210329-p57f1m.html">withdrew charges</a> against her and will pursue a civil case. In the meantime, broader questions about her fate remain. </p>
<p>Did Caddick take her own life from the cliffs near her home? How did her remains wash up on a remote beach 400 kilometres away? And why was her foot, still clad in a running shoe, the only trace found after more than three months?</p>
<p>We are oceanographers, and cannot speculate about what happened in Caddick’s final hours. However, our experience shows how tragedy – and sometimes luck – can reveal hidden ocean highways that connect every part of the planet.</p>
<figure class="align-center ">
<img alt="Homes atop ocean cliff face" src="https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393006/original/file-20210401-13-5h0pvf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The cliffs near Dover Heights, where Melissa Caddick was last seen.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What is an ocean current?</h2>
<p>Ocean currents are found at both the ocean’s surface and in deep water. They are driven by a combination of wind, tides, water density differences and Earth’s rotation. Currents <a href="https://www.nationalgeographic.org/media/ocean-currents-and-climate/">move</a> water horizontally and vertically and occur on <a href="https://oceanservice.noaa.gov/facts/current.html">both</a> local and global scales.</p>
<p>Monitoring currents is important for understanding how floating objects, marine life, pollutants, and nutrients travel through the ocean. It can also help determine the most efficient shipping routes. </p>
<p>And, as climate change worsens, tracking currents can tell us how heat energy in the ocean is moving around the planet.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-current-affair-the-movement-of-ocean-waters-around-australia-96779">A current affair: the movement of ocean waters around Australia</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="Ocean whirlpool" src="https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393019/original/file-20210401-15-1b46myc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s important for scientists to understand ocean currents.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The fickle sea</h2>
<p>Ocean currents are unpredictable. When someone falls into the water, by accident or otherwise, it can be hard to predict where the current will take them.</p>
<p>This is illustrated by an experiment which, by coincidence, we conducted along the same stretch of coast around the time Caddick is thought to have entered the water. Our <a href="http://oceanography.unsw.edu.au/">research group</a> deployed several satellite-tracked floating buoys, or drifters, off Port Stephens, about 150km north of Sydney. We wanted to <a href="http://oceancurrent.imos.org.au/news.php#Drifting_to_shore">study</a> the effects of currents, wind and waves on objects drifting on the ocean surface.</p>
<p>On November 10 – the day before Caddick was last seen alive – we deployed two biodegradable drifters about 40km offshore. We released a third drifter on December 2, in the same patch of ocean.</p>
<p>We then tracked the drifters’ positions until they beached more than a month later – and discovered they took very different paths. One drifter was carried as far as Jervis Bay, 250km southwest. The second travelled 180km southwest to Wollongong. And the third drifter moved north, eventually washing up in Worimi National Park near Newcastle, not far from where it was deployed. </p>
<p>So it’s certainly possible a buoyant object such as a shoe could float several hundred kilometres over several months. And as our experiment shows, it’s hard to predict where it will end up.</p>
<figure class="align-center ">
<img alt="Map showing the routes three " src="https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393034/original/file-20210401-15-13b8gmy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Authors supplied</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The tale of Moby-Duck</h2>
<p>Drifting buoys are a rough approximation of a detached foot in a running shoe – often the most buoyant and well-preserved part of a decomposing body.</p>
<p>In one well-publicised case, <a href="https://www.smh.com.au/national/how-21-feet-washing-up-on-canadian-shores-may-provide-clue-in-caddick-case-20210301-p576uy.html">21 feet</a> – mostly in running shoes – washed up over a decade on the coasts of British Columbia, in Canada, and the neighbouring US state of Washington. A 2017 inquest <a href="https://www.smh.com.au/national/how-21-feet-washing-up-on-canadian-shores-may-provide-clue-in-caddick-case-20210301-p576uy.html">ruled out</a> foul play, noting the most likely cause of death in each case was suicide or accident.</p>
<p>Thankfully, drifting objects are not always so gruesome. Bottles (<a href="https://www.theatlantic.com/technology/archive/2012/09/found-worlds-oldest-message-in-a-bottle-part-of-1914-citizen-science-experiment/261981/">containing messages</a>), adrift <a href="https://www.theguardian.com/world/2015/nov/07/fisherman-lost-at-sea-436-days-book-extract">sailors</a>, and even thousands of unopened <a href="https://www.atlasobscura.com/places/shipwrecked-doritos">packets of Doritos</a> have washed ashore, sometimes after years at sea.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/for-decades-scientists-puzzled-over-the-plastic-missing-from-our-oceans-but-now-its-been-found-133434">For decades, scientists puzzled over the plastic 'missing' from our oceans – but now it's been found</a>
</strong>
</em>
</p>
<hr>
<p>Another famous incident happened in 1992, when a cargo ship in the North Pacific lost a container holding <a href="https://www.npr.org/2011/03/29/134923863/moby-duck-when-28-800-bath-toys-are-lost-at-sea">28,800 yellow rubber ducks</a> and other bath toys. As the map below shows, the <a href="https://en.wikipedia.org/wiki/Friendly_Floatees">colourful toys</a> made their way around the world.</p>
<p>The story, recounted by journalist Donovan Hohn in his book <a href="https://www.npr.org/2011/03/29/134923863/moby-duck-when-28-800-bath-toys-are-lost-at-sea">Moby-Duck</a>, has a dark side. The toys form part of an endless river of plastic that flows into our oceans, collecting in giant floating “<a href="https://www.nationalgeographic.org/encyclopedia/great-pacific-garbage-patch/">garbage patches</a>” where currents and winds converge. Much of this plastic persists for decades, making its way into the food chain and ultimately the stomachs of birds, fish, and mammals.</p>
<figure class="align-center ">
<img alt="Map showing path taken by floating bath toys" src="https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=464&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=464&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393024/original/file-20210401-13-1yrey9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=464&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Map showing path taken by floating bath toys.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Friendly_Floatees.png">Wikimedia</a></span>
</figcaption>
</figure>
<h2>A surprising ocean odyssey</h2>
<p>Our experiment demonstrates another feature of the ocean off Australia’s east coast: the gradual southward drift known as the <a href="https://iview.abc.net.au/show/australia-s-ocean-odyssey-a-journey-down-the-east-australian-current">East Australian Current</a>. The EAC, as it is fondly known, brings warm, tropical water southwards along the coast of Queensland and NSW into the Tasman Sea. </p>
<p>Despite its reputation as a swift, smoothly flowing river of seawater – as depicted in the movie Finding Nemo – the EAC is actually highly variable. It meanders, loops, and sometimes pinches off to form swirling vortices called eddies, hundreds of kilometres across. At times it can flow northwards, or move well offshore. This video shows how variable the EAC can be: </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/9byTc-X_ky8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Eastern Australian current over 22 years, sea surface temperature (SST) vs sea level anomaly (SLA).</span></figcaption>
</figure>
<p>The combination of current, winds and waves can carry floating debris on surprising voyages. In one recent example, a surfboard lost off the south coast of Tasmania spent nearly two years at sea before being recovered, encrusted with barnacles, by fishermen <a href="https://www.theguardian.com/australia-news/2021/mar/17/stoked-surfboard-lost-in-tasmania-turns-up-2700km-away-in-queensland">2,700km away</a> in northern Queensland.</p>
<p>The surfboard’s journey northward is puzzling because the EAC generally flows in the opposite direction. One theory is the surfboard went “the long way” around New Zealand before drifting back towards Queensland. Alternatively, it could have been carried by winds and waves, which often blow from the south in this region. It could even have been passed from one ocean eddy to another in a sort of oceanic game of pass-the-parcel.</p>
<p>The fishermen were eventually able to reunite the surfboard with its grateful owner after cleaning off the barnacles. That’s slightly unfortunate, because those barnacles were a kind of biological message-in-a-bottle. Analysis of the different species on the board might have enabled scientists to retrace the surfboard’s ocean odyssey. </p>
<p>For now, that too remains a mystery.</p>
<hr>
<p><em>If you are having suicidal thoughts, call Lifeline at 13 11 14. If you are worried about a loved one or have lost someone to suicide, find support and information at <a href="https://www.beyondblue.org.au/the-facts/suicide-prevention">Beyond Blue</a>.</em></p><img src="https://counter.theconversation.com/content/158219/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shane Keating receives funding from the Australian Research Council to carry out research into the ocean circulation around Australia. </span></em></p><p class="fine-print"><em><span>Moninya Roughan receives funding from the Australian Research Council to carry out research into ocean circulation around Australia</span></em></p>The grisly discovery of a disembodied foot on a NSW beach was a tragic twist in the mystery of missing woman Melissa Caddick. Such tragedies can also reveal hidden currents connecting the planet.Shane Keating, Senior Lecturer in Mathematics and Oceanography, UNSW SydneyMoninya Roughan, Professor in Oceanography, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/580552016-04-19T06:26:00Z2016-04-19T06:26:00ZWas Tasmania’s summer of fires and floods a glimpse of its climate future?<p><a href="http://www.bom.gov.au/climate/drought/archive/20160108.shtml">Drought</a>, <a href="https://theconversation.com/fires-in-tasmanias-ancient-forests-are-a-warning-for-all-of-us-53806">fires</a>, <a href="http://www.abc.net.au/news/2016-01-29/more-rain-expected-in-tasmanian-flash-flooding-zones/7123014">floods</a>, <a href="http://www.themercury.com.au/news/opinion/species-on-the-move-worldwide/news-story/8a7caf95adeb512c64308504bcf42ceb">marine heatwaves</a> – Tasmania has had a tough time this summer. These events damaged its natural environment, including world heritage forests and alpine areas, and affected homes, businesses and energy security.</p>
<p>In past decades, climate-related warming of Tasmania’s land and ocean environments has seen <a href="http://www.themercury.com.au/news/opinion/species-on-the-move-worldwide/news-story/8a7caf95adeb512c64308504bcf42ceb">dozens of marine species moving south</a>, contributed to dieback in several tree species, and <a href="http://www.abc.net.au/news/2014-07-28/climate-change-driving-a-boom-in-tasmanian-wine-industry/5627836">encouraged businesses and people from mainland Australia to relocate</a>. These slow changes don’t generate a lot of attention, but this summer’s events have made people sit up and take notice. </p>
<p>If climate change will produce conditions that we have never seen before, did Tasmania just get a glimpse of this future?</p>
<h2>Hot summer</h2>
<p>After the <a href="http://www.abc.net.au/news/2015-08-31/tasmania-shivers-through-coldest-winter-in-50-years/6738326">coldest winter in half a century</a>, Tasmania experienced a warm and very dry spring in 2015, including a record dry October. During this time there was a <a href="https://theconversation.com/hasta-la-vista-el-nino-but-dont-hold-out-for-normal-weather-just-yet-53565">strong El Niño event</a> in the Pacific Ocean and a <a href="https://theconversation.com/droughts-and-flooding-rains-it-takes-three-oceans-to-explain-australias-wild-21st-century-weather-56264">positive Indian Ocean Dipole event</a>, both of which <a href="https://theconversation.com/when-the-indian-ocean-and-el-nino-join-forces-things-can-get-hot-and-dry-48969">influence Tasmania’s climate</a>. </p>
<p>The dry spring was followed by Tasmania’s warmest summer since records began in 1910, with temperatures 1.78°C above the long-term average. Many regions, especially the west coast, stayed dry during the summer – a pattern consistent with <a href="http://dpipwe.tas.gov.au/conservation/climate-change/climate-futures-for-tasmania">climate projections</a>. The dry spring and summer led to a reduction in available water, including a reduction of inflows into reservoirs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=222&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=222&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=222&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=279&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=279&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119189/original/image-20160419-5318-7gtsjs.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=279&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: September-November 2015 rainfall, relative to the long-term average. Right: December 2015-February 2016 temperatures, relative to the long-term average.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Is warmer better? Not with fires and floods</h2>
<p>Tourists and locals alike enjoyed the clear, warm days – but these conditions came at a cost, priming Tasmania for damaging bushfires. Three big lightning storms struck, including one on January 13 that delivered almost 2,000 lightning strikes and sparked many fires, particularly in the state’s northwest. </p>
<p>By the end of February, more than 300 fires had burned more than 120,000 hectares, including more than 1% of Tasmania’s World Heritage Area – alpine areas that had not burnt since the end of the last ice age some 8,000 years ago. Their fire-sensitive cushion plants and endemic pine forests are <a href="https://theconversation.com/fires-in-tasmanias-ancient-forests-are-a-warning-for-all-of-us-53806">unlikely to recover</a>, due to the loss of peat and soils. </p>
<p>Meanwhile, the state’s emergency resources were further stretched by heavy rain at the end of January. This caused flash flooding in several east coast towns, some of which received their highest rainfall ever. Launceston experienced its <a href="https://theconversation.com/fires-in-tasmanias-ancient-forests-are-a-warning-for-all-of-us-53806">second-wettest day on record</a>, while Gray recorded 221 mm in one day, and 489 mm over four days. </p>
<p>Flooding and road closures isolated parts of the state for several days, and many businesses (particularly tourism) suffered weeks of disruption. The extreme rainfall was caused by an intense low-pressure system – the <a href="http://dpipwe.tas.gov.au/conservation/climate-change/climate-futures-for-tasmania">Climate Futures for Tasmania</a> project has predicted that this kind of event will become more frequent in the state’s northeast under a warming climate.</p>
<h2>Warm seas</h2>
<p>This summer, an extended <a href="http://www.sciencedirect.com/science/article/pii/S0079661116000057">marine heatwave</a> also developed off eastern Tasmania. Temperatures were 4.4°C above average, partly due to the warm <a href="http://theconversation.com/this-summers-sea-temperatures-were-the-hottest-on-record-for-australia-heres-why-56906">East Australian Current</a> extending southwards. The heatwave began on December 3, 2015, and was ongoing as of April 17 – the longest such event recorded in Tasmania since satellite records began in 1982. It began just days after the end of the second-longest marine heatwave on record, from August 31 to November 28, 2015, although that event was less intense.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=386&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=386&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=386&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119214/original/image-20160419-13910-10yj58j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Anatomy of a marine heatwave. Top left: summer sea surface temperatures relative to seasonal average. Top right: ocean temperature over time; red shaded region shows the ongoing heatwave. Bottom panels: duration (left) and intensity (right) of all recorded heatwaves; the ongoing event is shown in red.</span>
<span class="attribution"><span class="source">Eric Oliver</span></span>
</figcaption>
</figure>
<p>As well as months of near-constant heat stress, oyster farms along the east coast were devastated by a new disease, <a href="http://www.dpi.nsw.gov.au/content/fisheries/pests-diseases/animal-health/aquaculture/poms">Pacific Oyster Mortality Syndrome</a>, which killed 100% of juvenile oysters at some farms. The disease, which has previously affected New South Wales oyster farms, is thought to be linked to unusually warm water temperatures, although this is not yet proven.</p>
<h2>Compounding the damage</h2>
<p>Tasmania is often seen as having a mild climate that is less vulnerable to damage from climate change. It has even been portrayed as a “<a href="http://www.dpac.tas.gov.au/divisions/climatechange/Climate_Change_Priorities/about_us">climate refuge</a>”. But if this summer was a taste of things to come, Tasmania may be less resilient than many have believed. </p>
<p>The spring and summer weather also hit Tasmania’s hydroelectric dams, which were already <a href="https://theconversation.com/how-much-will-tasmania-pay-for-shorting-the-carbon-price-29106">run down during the short-lived carbon price</a> as Tasmania sold clean renewable power to the mainland. Dam levels are at an <a href="http://www.abc.net.au/news/2016-03-07/hydro-tasmania-in-uncharted-territory/7227494">all-time low and continue to fall</a>. </p>
<p>The situation has escalated into a looming energy crisis, because the state’s connection to the national electricity grid – the Basslink cable – has not been operational since late December. The state faces the prospect of meeting winter energy demand by running 200 leased diesel generators, at a cost of A$43 million and making major carbon emissions that can only exacerbate the climate-related problems that are already stretching the state’s emergency response capability.</p>
<p>Is this summer’s experience a window on the future? Further study into the causes of climate events, known as “detection and attribution”, can help us untangle the human influence from natural factors. </p>
<p>If we do see the fingerprint of human influence on this summer, Tasmania and every other state and territory should take in the view and plan accordingly. The likely concurrence of multiple events in the future – such as Tasmania’s simultaneous fires and floods at either end of the island and a heatwave offshore – demands that governments and communities devise new strategies and mobilise extra resources.</p>
<p>This will require unprecedented coordination and cooperation between governments at all levels, and between governments, citizens, and community and business groups. Done well, the island state could show other parts of Australia how to prepare for a future with no precedent.</p><img src="https://counter.theconversation.com/content/58055/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alistair Hobday receives research funding from the FRDC, AFMA, and the Department of Environment.</span></em></p><p class="fine-print"><em><span>Michael Grose receives funding from the Department of Environment. </span></em></p><p class="fine-print"><em><span>Eric Oliver and Jan McDonald do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>This summer has seen Tasmania suffer through drought, bushfires, floods and the worst marine heatwave on record. Is this what life under a climate-changed future will be like?Alistair Hobday, Senior Principal Research Scientist - Oceans and Atmosphere, CSIROEric Oliver, Postdoctoral Fellow (Physical Oceanography and Climate), University of TasmaniaJan McDonald, Professor of Environmental Law, University of TasmaniaMichael Grose, Climate Projections Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/427662015-07-14T04:53:19Z2015-07-14T04:53:19ZFollowing Nemo: marine life is heading south<figure><img src="https://images.theconversation.com/files/88156/original/image-20150713-9476-xg1kr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The tropical orange blotch surgeon fish has been moving south into New South Wales.</span> <span class="attribution"><a class="source" href="http://www.fishesofaustralia.net.au/home/species/1029">Graham Edgar / Reef Life Survey</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>Changing wildlife: this is the first article in a series looking at how key species such as bees, insects and fish respond to environmental change, and what this means for the rest of the planet.</em></p>
<p>The seas are warming. Collectively the oceans have absorbed more than 80% of the energy retained by the Earth through <a href="http://www.nature.com/nclimate/journal/v3/n10/full/nclimate1958.html">recent climate change</a>.</p>
<p>However, actual warming of the water has been very uneven, with some seas heating up much more quickly than others. Temperate rises have been most extreme where there are strong currents flowing from hot tropical regions towards the poles. </p>
<p>And as warmer seas move further south, tropical wildlife is going with them, giving us a dramatic insight into how global warming is changing our oceans. </p>
<h2>The EAC</h2>
<p>The East Australian current (the famous “EAC” used by migrating turtles in the movie <a href="https://www.youtube.com/watch?v=J_7c2y04FtA">Finding Nemo</a>) brings warm water from off Queensland down the New South Wales coast to Tasmania. <a href="http://rspb.royalsocietypublishing.org/content/281/1789/20140846">Similar currents</a> also exist off southwestern Australia, Japan, the eastern United States, southeastern Africa and southern Brazil. </p>
<p>Many marine creatures have a wandering <a href="http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjun04/jmclarvae.html">larval stage</a> in their life cycle. These are often microscopic creatures that are transported by waves and currents far from their parents. Some larvae can travel for months or even years before settling down in suitable habitat and metamorphosing into the more recognisable crab, shell, sea-star or fish that we see along the coast. </p>
<p>This life history means that marine animals can respond rapidly to changing water temperatures and currents. Like Nemo they can be swept down the coast and survive in newly warming environments. </p>
<p>So let’s follow Nemo and find out what is happening along the eastern coast of Australia right now. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JpV7NIJTxD0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Heading south, permanently</h2>
<p>The Solitary Islands are off the New South Wales Coast, just north of Coffs Harbour. They are the front line in the <a href="http://rspb.royalsocietypublishing.org/content/281/1789/20140846">tropicalisation</a> of temperate oceans. Tropical herbivorous fish are settling in increasing numbers; parrotfish and surgeonfish scrape at rocks and coral to remove and eat seaweeds. </p>
<p>These fish demolish existing kelp beds and eat any young plants that attempt to grow. This in turn allows coral larvae brought down by the EAC to settle and thrive. Coral reefs are on the move. </p>
<p>Further south, the eastern coast of Tasmania is being invaded by animals that previously were only found in New South Wales. <a href="http://www.redmap.org.au/">Recreational fishers, naturalists and scientists</a> have recorded almost <a href="http://www.sciencedirect.com/science/article/pii/S0959378014002015">50 newly arrived species</a>, some in abundance. </p>
<p>The <a href="http://onlinelibrary.wiley.com/enhanced/doi/10.1111/j.1365-2486.2008.01734.x/">best documented</a> is the <a href="http://www.redmap.org.au/species/2/34/">long spined or black sea-urchin</a>, which also grazes kelp and has created large “barrens” on rocky reefs all the way to southern Tasmania. </p>
<h2>No room to move</h2>
<p>So does this matter? Who cares if everything just gets moved around? Coral reefs in New South Wales may sound attractive but there are a variety of reasons why warming of marine environments is bad news. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86924/original/image-20150701-24260-1aetfnq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The long spined sea urchin, which creates ‘barrens’ by grazing seaweeds, has become established in warming seas off Tasmania.</span>
<span class="attribution"><span class="source">John Turnbull / Flickr</span></span>
</figcaption>
</figure>
<p>One big problem happens at the poleward end of large continents. Cooler species have nowhere to go. There is no suitable habitat to migrate to. </p>
<p>For example, there is a whole cluster of species that only occur in southern Tasmania, like the cute <a href="http://www.fishesofaustralia.net.au/home/species/2842">spotted handfish</a>. Rising temperatures and invading species could easily drive this and other species off Tasmania to extinction. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86923/original/image-20150701-24249-pwbnzz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The critically endangered spotted handfish lives only in southern Tasmania.</span>
<span class="attribution"><span class="source">Rick Stuart-Smith / Reef Life Survey</span></span>
</figcaption>
</figure>
<p>Not all species have a larval stage that can travel long distances, and such species could become marooned in areas with unsuitable temperatures. Many economically important animals such as rock lobsters, abalone and scallops like cool water and will become restricted in range and abundance.</p>
<h2>It’s not just the heat</h2>
<p>Rising temperatures are not the only calamitous result of climate change.</p>
<p>Sea levels are rising as a result both of melting ice and of the expansion in volume that occurs when water warms. This will not only affect the hundreds of millions of humans that live next to the coastline, as their properties are inundated and they are forced to migrate, but also the specialised animal and plants that live along the coastline. </p>
<p>The additional carbon dioxide in the atmosphere is also a pollutant in its own right. Its effect on ocean chemistry is to make it more acidic. But this is <a href="http://www.biolbull.org/content/226/3/167.short">perilous</a> for animals like corals and molluscs that make their skeletons from calcium carbonate. </p>
<p>The deep sea will be affected as well. Coral beds living a kilometre or so below sea level on seamounts off southern Tasmania will get <a href="http://www.nature.com/nclimate/journal/v5/n7/full/nclimate2611.html">squeezed</a> by rising temperatures and ocean acidification. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86830/original/image-20150630-5859-720zsq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">With rising seas, animals and plants that live on this wide Victorian rock platform will be pushed upwards to occupy a thin band on the cliff behind.</span>
<span class="attribution"><span class="source">Museum Victoria</span></span>
</figcaption>
</figure>
<p>We do not lack scientific data on these issues. Nothing has arisen that has shaken the scientific consensus that there will be lethal problems for marine animals and plants from a changing climate.</p>
<p>It is now a social and engineering problem. They key thing is that we move rapidly to decarbonise the global economy.</p>
<p><br>
<em>We will be publishing more articles in this series in the coming days.</em></p>
<hr>
<p><em>Tim will be on hand for an Author Q&A between 2 and 3pm AEST on Wednesday, July 15. Post your questions in the comments section below.</em></p><img src="https://counter.theconversation.com/content/42766/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim O'Hara does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>As warmer seas move further south, tropical wildlife is going with them, giving us a dramatic insight into how global warming is changing our oceans.Tim O'Hara, Senior Curator of Marine Invertebrates, Museums Victoria Research InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/318892014-11-20T19:23:52Z2014-11-20T19:23:52ZThings warm up as the East Australian Current heads south<figure><img src="https://images.theconversation.com/files/63843/original/6993fjq2-1415250008.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Warmer waters heading south – here's sunrise off Manly in New South Wales.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/respres/14952758674">Flickr/Jeff Turner</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Occasional erratic bursts southward of the East Australian Current (<a href="https://theconversation.com/can-you-surf-the-east-australian-current-finding-nemo-style-27392">EAC</a>) are thought to have moderated the weather of south-east Australia this autumn and winter and they continue to introduce tropical and sub-tropical marine species to Tasmanian waters.</p>
<p>Ocean monitoring by Australia’s <a href="http://imos.org.au/">Integrated Marine Observing System</a> is providing scientists with <a href="http://www.oceanclimatechange.org.au/content/index.php/site/report_card_extended_2/category/east_australian_current">significant new insights</a> into the changing structure of the EAC. Over the past 50 years <a href="http://www.sciencedirect.com/science/article/pii/S0967064513004487">sporadic warm bursts</a> have become more common as the EAC moves further south. With global warming, the warm burst we’ve seen this year may also become the norm.</p>
<p>Had our little friend <a href="https://theconversation.com/can-you-surf-the-east-australian-current-finding-nemo-style-27392">Nemo the clownfish</a> been riding the EAC this year he might have found himself holidaying in Tasmania rather than admiring the Sydney Opera House. He wouldn’t have been on the trip alone, though. Sea nettles (<em>Chrysaora</em>) have headed from their usual home in Sydney to be found for the first time ever in Tasmania and the <a href="http://www.gippslandtimes.com.au/story/2147650/stinger-jellyfish-mystery/">Gippsland Lakes</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62054/original/b6qdbk77-1413510766.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Chrysaora woodbridge</em>, or sea nettle, was found in surprising numbers in Tasmania this year.</span>
<span class="attribution"><span class="source">Lisa-ann Gershwin</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Waters in the EAC travel southward along the east coast of Australia, with most of it splitting from the coast near Sydney and heading for New Zealand. A small part of the current, known as the EAC Extension, works its way southward past Victoria and Tasmania.</p>
<p>A typical signature in this region are the large eddies, around 200 kilometres across and hundreds of metres deep. Some of the warm water is trapped here along with marine life.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=604&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=604&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=604&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=760&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=760&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=760&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The EAC starts at the Great Barrier Reef and travels south to Sydney before turning eastward to New Zealand. Some of the water can still push southward via a series of strong eddies.</span>
<span class="attribution"><span class="source">Eric Oliver</span></span>
</figcaption>
</figure>
<p>This year a larger proportion of the EAC was sent southward instead of breaking away to the east. Winter ocean temperatures off Bass Strait were around 19C, an increase of 4C. This impacted local fishing, beach conditions and the weather.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/86Qcjgh3myk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>In the video (above) the animation on the left shows the actual sea surface temperature and speed of the ocean currents. The animation on the right shows the difference in the temperature from average conditions.</p>
<p>Through autumn and winter, you can see two interesting changes occur. A strong warm current heads down the coast from Sydney to the coast of Victoria. At the same time, warm water peels off from the EAC and swirls around in large eddies as it meanders toward Tasmania.</p>
<h2>An unusual catch down south</h2>
<p>One advantage of warm eddies is the refuge they provide for tuna. They congregate in the centre of the eddy where the waters are warm and dine at the nutrient-rich edges.</p>
<p>Local fishers in north-east Tasmania report a remarkable year that allowed them to fish longer than usual, providing game fishers with more opportunities to catch tuna.</p>
<p>Last summer’s (2013-2014) warmth provided an abundance of skipjack and striped marlin, while winter brought a run of bluefin tuna.</p>
<p><a href="http://www.redmap.org.au/">Redmap</a> is a website where locals can report sightings of marine species that are unusual for a given area.</p>
<p>Last summer a manta ray, a tropical cartilaginous fish (in a group including rays and skates), was <a href="http://www.redmap.org.au/sightings/1191/">sighted</a> off the north-eastern coast of Tasmania. Previously the southern-most sighting of a manta ray was just south of Sydney.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/59760/original/b3dm6hnp-1411445845.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Manta birostris</em> spotted off north-east Tasmania on Australia Day 2014.</span>
<span class="attribution"><a class="source" href="http://www.redmap.org.au/sightings/1191/">Redmap/Leo Miller</a></span>
</figcaption>
</figure>
<p>Its not just <a href="http://www.abc.net.au/news/2014-02-06/giant-jellyfish-found-by-schoolboy-on-tasmanian-beach/5241570">new species visiting</a> Tassie either. Local jellyfish such as the Lion’s Mane (cyanea) – more commonly known as “snotty” – are usually quite elusive, but turned up in unprecedented numbers <a href="http://www.smh.com.au/environment/animals/new-species-of-giant-snotty-jellyfish-found-in-tasmania-20140206-323ko.html">last summer</a> in Tasmania.</p>
<h2>But there’s a catch</h2>
<p>This movement south of the EAC may have an impact on other systems, including our health. We rely on fish such as those from the Tasman Sea as a source of omega-3 fatty acids for our brain health. But the concentration of omega-3 fatty acids in the fish is likely to decrease <a href="http://www.sciencedirect.com/science/article/pii/S0967064513004499">with global warming</a>. </p>
<p>The original source of fatty acids come from algal species. As our waters warm, we will see more of the algae from the tropics take up residence in the south-east.</p>
<p>But the algae from the tropics are much smaller, which means more steps in the food chain from the algae to the fish we eat. The more steps in the food chain, the more the omega-3 fatty acids in the fish are replaced by fatty acids that are less favourable to brain health.</p>
<p>The warmer coastal waters also contributed to the <a href="http://www.bom.gov.au/climate/current/statements/scs49.pdf">balmy autumn</a> and winter in south-eastern Australia this year. Afternoon sea breezes cool coastal temperatures by drawing cool oceanic air onto the coast.</p>
<p><a href="https://theconversation.com/winter-heatwaves-are-nice-as-extreme-weather-events-go-27172">Sydney’s heat wave</a> in May this year had 19 consecutive days of 22C or more – this is partly due to the sea breezes failing to bring in the usual cooling air.</p>
<h2>What’s causing the EAC to move south?</h2>
<p>Over the past 50 years the EAC Extension has stretched about 350km further south. This extension doesn’t happen smoothly but in erratic bursts.</p>
<p>The southward extent of the EAC is controlled by the collective behaviour of the winds between Australia and South America. Over that same 50-year period these winds changed their pattern due to a strengthening of a climate system known as the <a href="https://theconversation.com/new-zealand-is-drying-out-and-heres-why-32330">Southern Annular Mode</a>.</p>
<p>The changes to this mode have been <a href="http://onlinelibrary.wiley.com/doi/10.1029/2004GL020724/abstract">attributed</a> to a combination of ozone depletion and increasing atmospheric CO<sub>2</sub>.</p>
<p>One of the most <a href="http://onlinelibrary.wiley.com/doi/10.1029/2005GL024701/abstract">robust and consistent responses</a> of the climate system to increasing CO<sub>2</sub> is a further strengthening of the Southern Annular Mode.</p>
<p>So the result will likely be a further enhancement of the EAC extension southward and even warmer waters in the Tasman Sea.</p><img src="https://counter.theconversation.com/content/31889/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaci Brown does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Occasional erratic bursts southward of the East Australian Current (EAC) are thought to have moderated the weather of south-east Australia this autumn and winter and they continue to introduce tropical…Jaci Brown, Senior Research Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/273922014-06-05T20:37:34Z2014-06-05T20:37:34ZCan you surf the East Australian Current, Finding Nemo-style?<p>The animated movie <a href="http://www.imdb.com/title/tt0266543/">Finding Nemo</a> is responsible for most children’s (and parents’) image of the East Australian Current.</p>
<blockquote>
<p>Marlin: “I need to get to the East Australian Current – E A C.” <br>
Crush: “You’re ridin’ it dude. Check it out!”</p>
</blockquote>
<p>And so Marlin, the father of little clownfish Nemo, rides on the back of a turtle as they hitch a ride on the East Australian Current all the way to Sydney. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/J_7c2y04FtA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">‘Surfing’ the East Australian Current.</span></figcaption>
</figure>
<p>But did Hollywood tell us the truth about what happens in our own backyard?</p>
<p>Well, the movie may have added just a little poetic license to the real ways of the ocean. The East Australian Current is not the fast-flowing warp-tube as it’s portrayed in the movie – it’s an even better ride than that.</p>
<h2>Let the current flow</h2>
<p>The East Australian Current plays a crucial role in our east-coast climate and ecosystems. As it is <a href="http://worldoceansday.org/">World Oceans Day</a> this weekend (June 8), it’s a good time to have a closer look at the big current in our own backyard and what it does for us.</p>
<p>Let’s start with what’s correct in the movie. The East Australian Current does flow along the East coast of Australia, obviously. And it does flow southward from the Great Barrier Reef. Speeds in the core of the EAC are among the strongest in the South Pacific, up to 7km an hour.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=604&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=604&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=604&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=760&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=760&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50243/original/b7cmzjx2-1401863367.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=760&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The East Australian Current – more a ribbon than a tube.</span>
<span class="attribution"><span class="source">Eric Oliver</span></span>
</figcaption>
</figure>
<p>The movie would have you think that the East Australian Current is a narrow jet that you can jump in and out of as your thrill-seeking self desires. But actually the real East Australian Current is much bigger and much wilder than in the movie – just not so conducive to surfing.</p>
<p>It transports a staggering 40 million cubic metres of water southward each second. That is the equivalent of 16,000 Olympic swimming pools flowing along our coastline, every second. The current is almost 100km wide, and more than 1.5km deep – in fact, more like a ribbon than a tube.</p>
<h2>Why does the East Australian Current exist?</h2>
<p>The wind systems over the ocean and the spin of the Earth cause water in both hemispheres to slowly flow toward the equator in what’s called the subtropical <a href="http://oceanmotion.org/html/background/geostrophic-flow.htm">gyres</a> (also where all our plastics ends up in the infamous <a href="http://plastinography.org">garbage patches</a>).</p>
<p>Obviously, the water that flows towards the equator has to go somewhere. It does so in strong currents trapped tightly against the eastern coasts of landmasses. </p>
<p>Our East Australian Current is part of a family of five. All subtropical ocean basins have one of these western boundary currents:</p>
<ol>
<li>the Gulf Stream in the North Atlantic Ocean</li>
<li>the Brazil Current in the South Atlantic Ocean</li>
<li>the Agulhas Current in the Indian Ocean</li>
<li>the Kuroshio Current in the North Pacific Ocean</li>
<li>the East Australian Current in the South Pacific Ocean.</li>
</ol>
<p>Each of these is set up by the same wind patterns. The theory that explains western boundary currents was developed by Norwegian oceanographer Harald Sverdrup and was one of the major accomplishments of physical oceanography in the 1940s.</p>
<h2>Here come the eddies</h2>
<p>Once the East Australian Current reaches New South Wales, the current breaks up into a train of giant, 100km-wide vortices.</p>
<p>These so-called eddies are giant droplets of warm tropical water, and they slowly move south while rotating anti-clockwise at 5 to 10km per hour. The amount of eddies passing along the NSW coast is so large that some have termed the region “<a href="http://www.famer.unsw.edu.au/publications/Everett2012a.pdf">Eddy Avenue</a>”. </p>
<p>For many people, the eddies and strength of the East Australian Current become worth millions of dollars as the Sydney to Hobart yacht race kicks off on Boxing Day each year. If you’re on the wrong side of the eddy, the current is against you in your race south. Choosing the right path around the eddies is big business.</p>
<p>Apart from yachts, the EAC also transports marine species southward with tropical fish – including Marlin and Dory in their search to find Nemo – finding themselves in subtropical latitudes.</p>
<h2>A change in the EAC</h2>
<p>Climate change is already having an impact on the East Australian Current. The part south of Sydney has warmed up very fast, <a href="http://www.smh.com.au/environment/eastern-australian-waters-warming-fastest-20140331-35to0.html">much faster</a> than most of the rest of the ocean. And this warming is expected to continue in the future, with the current probably getting faster and stronger as well.</p>
<p>The warmer water being carried south to Tasmania already has an impact on marine life there. With warmer water, new species such as the spiny sea urchin arrive.</p>
<p>These new species, as well as the warmer water itself, <a href="http://www.abc.net.au/science/articles/2013/07/31/3811486.htm">slowly destroy</a> Tasmania’s kelp forests, which support unique marine ecosystems, transforming them into rocky barrens.</p>
<p>One of the most iconic kelp species, <em>Macrosystis pyrifera</em> or “giant kelp”, forms underwater forests up to 30m tall and is <a href="http://sixtyminutes.ninemsn.com.au/stories/charleswooley/259195/the-last-stand">rapidly disappearing</a> along Tasmania’s shores.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ZQb9ZFWfNZE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The giant kelp forests off Tasmania are quickly disappearing.</span></figcaption>
</figure>
<p>Such large relocations of marine ecosystems can occur more often in a warming ocean. Species will be forced to move southward as their water temperature “at home” increases.</p>
<p>While this might be bad for all ecosystems, it is particularly dire for species now living in Tasmania. Unlike the tropical species in Queensland or the temperate species in New South Wales, <a href="http://www.smh.com.au/articles/2007/03/16/1173722745030.html">which can move southwards</a> (albeit not without problems), Tasmanian species have nowhere to go.</p>
<p>If they try to move southward they encounter the edge of the continental shelf. With the next piece of habitable shelf more than 3,000km to the south in Antarctica, that’s the end of the line.</p><img src="https://counter.theconversation.com/content/27392/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Erik van Sebille receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Eric Oliver and Jaci Brown do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The animated movie Finding Nemo is responsible for most children’s (and parents’) image of the East Australian Current. Marlin: “I need to get to the East Australian Current – E A C.” Crush: “You’re ridin…Erik van Sebille, Research Fellow and Lecturer in Oceanography, UNSW SydneyEric Oliver, Postdoctoral Fellow (Physical Oceanography and Climate), University of TasmaniaJaci Brown, Senior Research Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.