tag:theconversation.com,2011:/us/topics/gulf-stream-5426/articlesGulf Stream – The Conversation2023-08-10T08:14:23Ztag:theconversation.com,2011:article/2112212023-08-10T08:14:23Z2023-08-10T08:14:23ZAtlantic collapse: Q&A with scientists behind controversial study predicting a colder Europe<p><em>In late July, <a href="https://www.nature.com/articles/s41467-023-39810-w">a study published in Nature Communications</a> warned that a critical ocean system that brings warm water up the North Atlantic, also known as the Atlantic Meridional Overturning Circulation (AMOC), was at risk of collapse by 2095 for want of drastic emissions cuts. While AMOC was already known to be at its slowest in 1600 years, the latest research ushers in a much closer time estimation for a collapse between 2025 and 2095, with a central estimate of 2057. If proven correct, this scenario could see temperatures drop by 5 to 10 degrees in Europe, with devastating consequences for life as we know it. The Conversation sat down with physicist Peter Ditlevsen and his sister, the statistician Susanne Ditlevsen, to unpack findings that have stirred controversy in some quarters.</em></p>
<p><strong>Your study understandably attracted much media attention, with some of the coverage conflating a collapse of the Gulf Stream with a collapse of AMOC. What did you make of this at the time?</strong></p>
<p>Susanne Ditlevsen: I think there are two aspects to this question. One is that the general public might confuse the Gulf stream and the AMOC and, in a certain sense, that’s just wording. So there is a current that brings warm water up and this is in danger of collapsing – whether we call it the AMOC or the Gulf Stream even though the Gulf Stream is something different in a certain sense doesn’t matter if it’s just a question of wording. </p>
<p>On the other, this misunderstanding can also be very harmful because there are people who know that the Gulf Stream cannot collapse, as it is driven by wind and the rotation of the earth. So when it comes out that we have predicted that the Gulf Stream will collapse, they might be tempted to dismiss us as idiots. </p>
<p>Ultimately, though, we don’t really care about the wording because sometimes people call it the Gulf Stream system which is the Gulf Stream and AMOC, and you can say ‘Well, okay’. I think it is important to explain that we are actually talking about something different, which we and many others do believe can collapse. </p>
<p>Our confidence interval – which spans 2025 to 2095 – was also misrepresented. There’s not the same probability across the entire interval. So we find it highly unlikely that a collapse could happen as early as 2025. </p>
<p>It is notoriously difficult to estimate what we call the <em>tails of the distribution</em> in statistical jargon. These are the smaller probabilities at the extremes of the distribution. However, the central estimate, situated at the mid-century, is where we believe that there is the highest risk of a collapse should we continue greenhouse gas emissions at the current rate. </p>
<p>Now, even if we are uncertain about our estimates, the main message from is that there is a considerable or at least underestimated risk that this collapse might happen much earlier than what was previously thought.</p>
<p><strong>Let’s say the AMOC collapsed in 2057. What would this look like in concrete terms in Europe?</strong></p>
<p>Peter Ditlevsen: If you look at it from a climate perspective, the collapse would probably be very rapid, which means it would shut down in a number of decades. </p>
<p>So, it’s not like you have an ice age in two weeks. The Northern Atlantic region and Europe, in particular, would cool substantially. England would probably look like Northern Canada. On top of that, we have global warming. So it’s a little bit as if we’re driving a car and, you know, we press the speed pedal and the brake at the same time. </p>
<blockquote>
<p>“It’s a little bit as if we’re driving a car and we press the speed pedal and the brake at the same time”
Peter Ditlevsen</p>
</blockquote>
<p>The heat from the Pacific ocean that would not be transported to the North Atlantic would end up staying in the tropics. This is part of a completely different system, namely the El Niño system, which has strong implications for the warming that we’re seeing now. We currently have an El Niño building up in North Africa. I mean, in Algeria, they recently had <a href="https://www.lemonde.fr/en/algeria/article/2023/07/25/algeria-heat-wave-takes-toll-forces-climate-change-reckoning_6066267_221.html">night temperatures that did not go below 39.5 degrees</a>. </p>
<p>SD: What we must bear in mind here is that whatever we discuss is highly uncertain. The extent to which temperatures will vary is highly uncertain – some say five degrees, some say 10 degrees, some say more storms etc. But I think the takeaway message is that the implications would be devastating in terms of our ability to carry on living the way we do now, and to continue having agriculture in different places. You would probably have to change everything. And there would be densely populated places where one simply cannot live. </p>
<p>PD: Another thing to realize is that we have a hard time coping with fast changes. Our societies have historically coped with climate change through migrations. And we know how difficult this is for societies. My big concern is that we have three billion people living in tropical regions, where you have extended periods with 39 degrees that go on to become extended periods with 42 degrees. </p>
<p><strong>What were your expectations when you began this project? Did you foresee these dramatic results?</strong></p>
<p>PD: So I had set out to add more weight to the Intergovernmental Panel on Climate Change’s (IPCC) assessment, thanks to a robust methodology and observations I planned to then adjust. It turned out that our models situated the collapse much earlier than the IPCC’s. Obviously, I would have preferred the outcome of our study was less controversial because we are of course being attacked from all sides now. But that’s how science works, I guess. And this was actually also how Susanne got deeply involved, because it really needed much better statistics that I am capable of. </p>
<p>SD: We also believe that this problem is so important that if we do have indications in the data for an earlier or even considerably earlier collapse than what has been what is generally believed, we do have to put it out. That does not mean that our result is cut in stone. Of course not. Because data is noisy and we have indirect measurements. And of course, for every year we get more data, we can give better estimates.</p>
<p>We have climate changes that have huge implications on earth and also much, much larger implications than what was predicted. Just look at the extreme weather events that we have had this summer and the new temperature records. All this is happening earlier and stronger than what was predicted.</p>
<p><strong>There is indeed a pattern of climate science, in particular the IPCC, showing conservative forecasts. Take, for example, the speed at which the Arctic ice is melting by comparison to their prognosis that it was safe until at least 2050.</strong></p>
<p>SD: They’re always conservative results. And in that sense, you could say that this is one of the reasons also that I think it gives a little more credibility to our study because of course we did not want to go against the IPCC, but they have shown to be conservative in many aspects. </p>
<p><strong>Let’s try to talk about future research on this question. What fields at present are helpful to understand the effect of AMOC?</strong></p>
<p>PD: Yes, so I have been involved for many years in trying to understand the past climate that we see in the paleoclimatic records. From a historic point of view, the largest enigma we had in climate science has long been why ice ages happen.</p>
<p>In some sense, climate change is not really, you know, a puzzle. If you look at global temperature records on the one hand, and greenhouse gas concentration records on the other, they’re pretty much following each other. It’s a boring job that the climate models have there.</p>
<p>But what we see now with more and more frequent extremes, heat waves and storms and floodings, is the possibility of actually hitting a nonlinearity, a tipping point. That’s a much more challenging phenomenon to model. </p>
<p><strong>How can science better grasp the implications of an AMOC tipping point?</strong></p>
<p>SD: We definitely need more measurements of the AMOC. But we also have to understand that we cannot measure back in time. However, since we don’t and cannot have these very, very detailed measurements from pre-industrial times, before global warming, it’s also difficult to assess what the natural variability is and what the natural behaviour is before global warming. </p>
<p>PD: In a way, when you ask what is needed, I would say it’s everything. This is especially the case on the modelling side. I mean, these models would require at least in some sense to reproduce what we’ve seen before.</p>
<p>SD: Yes, and I also think that it’s important to stress how our work complements the very detailed models of the IPCC. One of the reasons why our research has been so criticized is that we don’t have an explanation for the outcome we observe. We know what the driver is, but we don’t have that in our model. </p>
<p>And that is deliberate because we cannot measure the driver in a detailed enough fashion to include it into our model. On the other hand, you could also criticize the big models that are not based on good enough or detailed enough data. There’s a lot of speculation to them. I mean, there are so many variables and so many parameters. So in that sense, our method has a strength of really looking at the data, but without all the mechanisms, and then you have all the models that have all the mechanisms but do not necessarily fit to data. And that combination is extremely important and useful. </p>
<p><strong>But some fields are still managing to gather data by studying past sediments, right?</strong></p>
<p>PD: Yes, we do have huge sediment records. The problem is that in the case of the time scales that we’re looking at, any indications of tipping points will be washed out. This is because the temporal resolution in these records simply isn’t good enough. </p>
<p>But obviously, it would be incredible if someone came up with new types of paleo data. Every now and then, you look at stalagmites and stalactites which look like they could be used… So what we really need now is for smart young people with an open mind to come over, and try new crazy things that the old guys thought were impossible.</p><img src="https://counter.theconversation.com/content/211221/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Les auteurs ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'ont déclaré aucune autre affiliation que leur organisme de recherche.</span></em></p>If proven correct, the Danish scientists’ scenario could mean the end of life in Europe as we know it.Peter Ditlevsen, Professor in physics of ice, climate and earth, University of CopenhagenSusanne Ditlevsen, Professor in statistics, University of CopenhagenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2107732023-08-03T22:28:20Z2023-08-03T22:28:20ZThe ‘Gulf Stream’ will not collapse in 2025: What the alarmist headlines got wrong<figure><img src="https://images.theconversation.com/files/541040/original/file-20230803-23-57b5b3.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5379%2C3581&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is the sun setting on the Atlantic ocean current system? While not impossible, it is certainly not imminent, and overly sensationalist headlines do little to further the cause of tackling the climate crisis. </span> <span class="attribution"><span class="source">(AP Photo/Robert F. Bukaty)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/the-gulf-stream-will-not-collapse-in-2025-what-the-alarmist-headlines-got-wrong" width="100%" height="400"></iframe>
<p>Those following the latest developments in climate science would have been stunned by the jaw-dropping headlines last week proclaiming the <a href="https://www.theguardian.com/environment/2023/jul/25/gulf-stream-could-collapse-as-early-as-2025-study-suggests">“Gulf Stream could collapse as early as 2025, study suggests”</a> — which responded to a <a href="https://doi.org/10.1038/s41467-023-39810-w">recent publication in <em>Nature Communications</em></a>.</p>
<p>“Be very worried: Gulf Stream collapse could spark global chaos by 2025” <a href="https://nypost.com/2023/07/27/gulf-stream-collapse-could-spark-global-chaos-in-2-years/">announced the <em>New York Post</em></a>. “A crucial system of ocean currents is heading for a collapse that ‘would affect every person on the planet” noted <a href="https://www.cnn.com/2023/07/25/world/gulf-stream-atlantic-current-collapse-climate-scn-intl/index.html">CNN in the U.S.</a> and repeated <a href="https://www.ctvnews.ca/climate-and-environment/a-crucial-system-of-ocean-currents-is-heading-for-a-collapse-that-would-affect-every-person-on-the-planet-1.6495208">CTV News here in Canada</a>.</p>
<p>One can only imagine how <a href="https://doi.org/10.1038/s41558-023-01617-4">those already stricken with climate anxiety</a> internalized this seemingly apocalyptic news as <a href="https://theconversation.com/temperature-records-shattered-across-the-world-as-tourists-flock-to-experience-the-heat-210038">temperature records were being shattered</a> across the globe.</p>
<p>This latest alarmist rhetoric provides a textbook example of how not to communicate climate science. These headlines do nothing to raise public awareness, let alone influence public policy to support climate solutions. </p>
<h2>We see the world we describe</h2>
<p>It is well known that <a href="https://doi.org/10.1038/s41558-021-01251-y">climate anxiety is fuelled by media messaging about the looming climate crisis</a>. This is causing many to simply shut down and give up — <a href="https://www.vox.com/the-highlight/23622511/climate-doomerism-optimism-progress-environmentalism">believing we are all doomed and there is nothing anyone can do about it</a>.</p>
<figure class="align-center ">
<img alt="Vegetation burns in a desert environment." src="https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541102/original/file-20230803-18725-e09g42.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">While the consequences of global warming from forest fires to floods are real, overly alarmist rhetoric serves only to intensify climate anxiety.</span>
<span class="attribution"><span class="source">(AP Photo/Ty ONeil)</span></span>
</figcaption>
</figure>
<p>Alarmist media framing of impending doom has become <a href="https://www.ippr.org/files/images/media/files/publication/2011/05/warm_words_1529.pdf">quintessential fuel for personal climate anxiety</a>, and when amplified by sensational media messaging, it is quickly emerging as a dominant factor in the <a href="https://www.cbc.ca/books/generation-dread-by-britt-wray-1.6613335">collective zeitgeist of our age, the Anthropocene</a>.</p>
<p>This is also not the first time such headlines have emerged. Back in 1998, the <a href="https://www.theatlantic.com/magazine/archive/1998/01/the-great-climate-flip-flop/308313/"><em>Atlantic Monthly</em></a> published an article raising the alarm that global “warming could lead, paradoxically, to drastic cooling — a catastrophe that could threaten the survival of civilization.”</p>
<p>In 2002, editorials in the <a href="https://www.nytimes.com/2002/04/18/opinion/the-heat-before-the-cold.html"><em>New York Times</em></a> and <a href="https://www.discovermagazine.com/environment/the-next-ice-age"><em>Discover</em></a> magazine offered the prediction of a forthcoming collapse of deep water formation in the North Atlantic, which would lead to the next ice age. </p>
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Read more:
<a href="https://theconversation.com/do-phrases-like-global-boiling-help-or-hinder-climate-action-210960">Do phrases like 'global boiling' help or hinder climate action?</a>
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<p>Building on the unfounded assertions in these earlier stories, BBC Horizon televised a 2003 documentary entitled <a href="https://www.bbc.co.uk/science/horizon/2003/bigchill.shtml"><em>The Big Chill</em></a>, and in 2004 <a href="https://fortune.com/2014/01/12/the-pentagons-weather-nightmare-fortune-2004/"><em>Fortune</em></a> magazine published “The Pentagon’s Weather Nightmare,” piling on where previous articles left off.</p>
<p>Seeing the opportunity for an exciting disaster movie, Hollywood stepped up to created <a href="https://www.imdb.com/title/tt0319262/"><em>The Day After Tomorrow</em></a> in which every known law of thermodynamics was ever so creatively violated.</p>
<h2>The currents are not collapsing (anytime soon)</h2>
<p>While it was <a href="https://journals.lib.unb.ca/index.php/GC/article/view/2753">relatively easy</a> to show that it is <a href="https://doi.org/10.1126/science.1096503">not possible for global warming to cause an ice age</a>, this still hasn’t stopped some from <a href="https://www.wgbh.org/news/commentary/2021/03/24/weve-known-for-years-global-warming-could-lead-to-a-new-ice-age-why-is-no-one-doing-anything">promoting</a> this false narrative. </p>
<p>The latest series of alarmist headlines may not have fixated on an impending ice age, but they still suggest the Atlantic meridional overturning circulation could collapse by 2025. This is an outrageous claim at best and a completely irresponsible pronouncement at worst.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of the flow of the Atlantic meridional overturning circulation" src="https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=473&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=473&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=473&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=594&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=594&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540965/original/file-20230803-29-rvsblt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=594&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Diagram of the flow of the Atlantic meridional overturning circulation.</span>
<span class="attribution"><span class="source">R. Curry, Woods Hole Oceanographic Institution/Science/USGCRP</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>The Intergovernmental Panel on Climate Change has been assessing the likelihood of a cessation of deep-water formation in the North Atlantic for decades. In fact, I was on the writing team of the <a href="https://www.ipcc.ch/report/ar4/wg1/">2007 4th Assessment Report</a> where we concluded that:</p>
<blockquote>
<p>“It is very likely that the Atlantic Ocean Meridional Overturning Circulation (MOC) will slow down during the course of the 21st century. It is very unlikely that the MOC will undergo a large abrupt transition during the course of the 21st century.”</p>
</blockquote>
<p>Almost identical statements were included in the <a href="https://www.ipcc.ch/report/ar5/wg1/">5th Assessment Report in 2013</a> and the <a href="https://www.ipcc.ch/report/ar6/wg1/">6th Assessment Report in 2021</a>. Other assessments, including the National Academy of Sciences <a href="https://nap.nationalacademies.org/catalog/18373/abrupt-impacts-of-climate-change-anticipating-surprises"><em>Abrupt Impacts of Climate Change: Anticipating Surprises</em></a>, published in 2013, also reached similar conclusions.</p>
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Read more:
<a href="https://theconversation.com/it-can-be-done-it-must-be-done-ipcc-delivers-definitive-report-on-climate-change-and-where-to-now-201763">'It can be done. It must be done': IPCC delivers definitive report on climate change, and where to now</a>
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<p>The 6th assessment report went further to conclude that:</p>
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<p>“There is no observational evidence of a trend in the Atlantic Meridional Overturning Circulation (AMOC), based on the decade-long record of the complete AMOC and longer records of individual AMOC components.”</p>
</blockquote>
<h2>Understanding climate optimism</h2>
<p>Hannah Ritchie, the deputy editor and lead researcher at <a href="https://ourworldindata.org/">Our World in Data</a> and a senior researcher at the Oxford Martin School, <a href="https://www.vox.com/the-highlight/23622511/climate-doomerism-optimism-progress-environmentalism">recently penned an article for <em>Vox</em></a> where she proposed an elegant framework for how people see the world and their ability to facilitate change. </p>
<p>Ritchie’s framework lumped people into four general categories based on combinations of those who are optimistic and those who are pessimistic about the future, as well as those who believe and those who don’t believe that we have agency to shape the future based on today’s decisions and actions.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram highlighting four main categories of climate communications." src="https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=523&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=523&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=523&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=657&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=657&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540964/original/file-20230803-25-i7fvqd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=657&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 sweetspot of climate communications strikes an optomistic tone while reinforcing that change is possible.</span>
<span class="attribution"><span class="source">(Andrew Weaver)</span>, <span class="license">Author provided</span></span>
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<p>Ritchie persuasively argued that more people located in the green “optimistic and changeable” box are what is needed to advance climate solutions. Those positioned elsewhere are not effective in advancing such solutions. </p>
<p>More importantly, rather than instilling a sense of optimism that global warming is a solvable problem, the extreme behaviour (fear mongering or civil disobedience) of the “pessimistic changeable” group (such as many within the <a href="https://rebellion.global/">Extinction Rebellion</a> movement), often does nothing more than drive the public towards the “pessimistic not changeable” group.</p>
<h2>A responsibility to communicate, responsibly</h2>
<p>Unfortunately, extremely low probability, and often poorly understood <a href="https://doi.org/10.1126/science.abn7950">tipping point scenarios</a>, often end up being misinterpreted as likely and imminent climate events. </p>
<p>In many cases, the <a href="https://doi.org/10.1073/pnas.1317504111">nuances of scientific uncertainty</a>, particularly around the differences between hypothesis posing and hypothesis testing, are lost on the lay reader when a study goes viral across social media. This is only amplified in situations where scientists make statements where creative licence is taken with speculative possibilities. Possibilities that reader-starved journalists are only too happy to play up in clickbait headlines.</p>
<figure class="align-center ">
<img alt="Delegates sit before a banner at COP27" src="https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541101/original/file-20230803-27-hjb3bf.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">
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<span class="caption">Climate scientists, practitioners and the media all have a responsibility to avoid sensationalism in discussing climate futures.</span>
<span class="attribution"><span class="source">(AP Photo/Peter Dejong)</span></span>
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</figure>
<p>Through independent research and the writing of IPCC reports, the climate science community operates from a position of privilege in the public discourse of climate change science, its impacts and solutions.</p>
<p>Climate scientists have agency in the advancement of climate solutions, and with that agency comes a responsibility to avoid sensationalism. By not tempering their speech, they risk further ratcheting up the rhetoric with nothing to offer in terms of overall solutions or risk reduction.</p><img src="https://counter.theconversation.com/content/210773/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Weaver receives research grant funding from Canada's Climate Action and Awareness Fund </span></em></p>Recent headlines around the supposed impending collapse of the Atlantic currents remind us of the importance of avoiding sensationalism in facing global warming.Andrew Weaver, Professor, School of Earth and Ocean Sciences, University of VictoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1846262022-06-15T18:13:06Z2022-06-15T18:13:06ZWhy the St. Lawrence estuary is running out of breath<figure><img src="https://images.theconversation.com/files/468234/original/file-20220610-41411-7sdug2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Estuary and Gulf of St. Lawrence is one of, if not the largest estuarine system on Earth. It plays an intrinsic role in the history of Canada and is the cradle of Quebec's economy, and its identity.</span> <span class="attribution"><span class="source">(Gwénaëlle Chaillou)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>There’s no sign of it on the surface, but the water at the bottom of the estuary of the Lower St. Lawrence River is running out of breath. There is less and less dissolved oxygen in this deep water, and this deoxygenation cannot be fixed.</p>
<p>Our research focuses on a range of marine geochemistry projects, including the causes and consequences of low oxygen, called hypoxia, in the deep waters of the Gulf of St. Lawrence and of the estuary.</p>
<h2>The colossal St. Lawrence River</h2>
<p>An estuary is a coastal body of water, where freshwater and salt water mix, that empties into an ocean. The St. Lawrence estuarine system is the largest on Earth. </p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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</figure>
<p><em>This article is part of our series, <a href="https://theconversation.com/ca-fr/topics/fleuve-saint-laurent-116908">The St. Lawrence River: In depth</a>.
Don’t miss new articles on this mythical river of remarkable beauty. Our experts look at its fauna, flora and history, and the issues it faces. This series is brought to you by <a href="https://theconversation.com/ca-fr">La Conversation</a>.</em></p>
<hr>
<p>The system connects the Great Lakes to the Atlantic Ocean, draining nearly 25 per cent of the world’s freshwater reserves. The average freshwater discharge at Québec City is about <a href="https://doi.org/10.1007/s10533-017-0371-4">12,000 cubic metres per second</a>, the second-largest freshwater discharge in North America, second only to the Mississippi River. </p>
<p>The St. Lawrence estuary begins at the eastern tip of Ile d’Orléans, east of Québec City. This is where the first traces of salt water can be found. It then extends over 400 kilometres to Pointe-des-Monts, where it widens and becomes the Gulf of St. Lawrence, an inland sea that is connected to the Atlantic Ocean by the Cabot Strait and the Strait of Belle Isle.</p>
<p>The estuary is separated into two segments: The upper estuary, which extends from Île d'Orléans to Tadoussac, near the mouth of the Saguenay Fjord, and the lower estuary, which runs from Tadoussac to Pointe-des-Monts. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map of Quebec with the St. Lawrence Estuary" src="https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=468&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=468&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=468&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468596/original/file-20220613-16-u56vk9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&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 St. Lawrence system and estuary.</span>
<span class="attribution"><span class="source">(Alfonso Mucci)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The upper estuary, or fluvial estuary, is relatively narrow (two to 24 kilometres wide) and shallow, generally less than 30 metres deep. There is a strong horizontal salinity gradient, a gradual increase in the amount of dissolved salt in the water.</p>
<p>From a vertical perspective, the water column is well mixed or weakly stratified. A water column is stratified when water masses of different densities (determined by temperature and salt content) are superimposed vertically. These water masses cannot mix easily without a significant input of energy.</p>
<p>The lower estuary, or marine estuary, is much wider (30 to 50 kilometres wide) and deeper. At its centre, a 1,240-kilometre long submarine valley plunges to a depth of more than 300 metres. This is the Laurentian Channel, and it’s where deoxygenation is occurring.</p>
<h2>Three layers of water</h2>
<p>To understand the causes of deoxygenation, it is important to know that the water column in the maritime estuary and the gulf is composed of three layers: </p>
<ol>
<li><p>A surface layer, 0-30 metres deep, of relatively warm and brackish water that flows toward the Atlantic. </p></li>
<li><p>A cold intermediate layer, 30-150 metres deep, that is almost as salty as sea water. It forms in the winter in the gulf and moves up the estuary. This layer contains 32 grams of dissolved salts for each kilogram of water. Lake or river water typically contains less than 0.01 grams per kilogram, and sea water contains nearly 35 grams per kilogram. </p></li>
<li><p>Dense, deep water exists below 150 metres. These are warmer (between 2 C and 7 C) and saltier (salinity between 33 and 35 grams per kilogram). These waters form on the continental slope near Cape Breton, N.S., through a mixing of cold, well-oxygenated water from the Labrador Current and warmer, less-oxygenated water from the <a href="https://doi.org/10.4319/lo.2005.50.5.1654">North Atlantic Central Water</a>.</p></li>
</ol>
<p>These dense waters line the bottom of the Laurentian Channel and migrate slowly towards Tadoussac, with a limited amount of dissolved oxygen that decreases during its transit as bacteria gradually consume the oxygen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic showing the depth of the St. Lawrence as it moves from Quebec City to the Atlantic Ocean, and the different water layers." src="https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468598/original/file-20220613-26-xc9z3m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stratification of different water masses in the St. Lawrence estuary, Gulf of St. Lawrence and Laurentian Channel.</span>
<span class="attribution"><span class="source">(Alfonso Mucci)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>History of deep water deoxygenation</h2>
<p><a href="https://doi.org/10.4319/lo.2005.50.5.1654">In 2003, a series of measurements</a> revealed that the deep waters of the maritime estuary, close to Rimouski, had very low levels of dissolved oxygen that fell below the threshold value for severe hypoxia (62.5 µmol/L or 20 per cent saturation). Below this threshold, several species of fish, such as cod, cannot survive long, and the structure and activity of benthic communities, such as molluscs and shrimp, that live deep near the bottom, are greatly modified. </p>
<p>Water with even lower concentrations of dissolved oxygen (60 µmol/L, or 18 per cent saturation) lines the bottom of the Laurentian Channel, creating a hypoxic zone that extended over approximately 1,300 square kilometres, from Tadoussac to Pointe-des-Monts.</p>
<p><a href="https://doi.org/10.4319/lo.2005.50.5.1654">Historical data</a> paired with data acquired between 2003 and 2021 reveal that dissolved oxygen concentrations in the deep waters of the estuary have been in deep decline over the past century. They were cut in half between 1934 and 1985 (decreasing to 60 µmol/L from 135 µmol/L), and then remained relatively stable until 2010. In 2021, however, the measured concentrations dropped even further to half what it had been just two years earlier (35 µmol/L).</p>
<p>In addition, deep waters with these low oxygen concentrations now extend to the gulf, tripling the area of the hypoxic zone in just 20 years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic showing the decrease in dissolved oxygen, 1925-2025." src="https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468599/original/file-20220613-26-32c0bc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Minimum dissolved oxygen concentrations in the Lower St. Lawrence estuary at depths greater than 250 metres. These data were recorded in a station near Rimouski.</span>
<span class="attribution"><span class="source">(Alfonso Mucci)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>What are the causes?</h2>
<p>Over the past century, as dissolved oxygen concentrations decreased, <a href="https://publications.gc.ca/site/eng/9.891309/publication.html">deep-water temperatures have also increased dramatically to 6 C from 3 C</a>. Micro-paleontological research — the counting and identification of fossil micro-organisms — and geochemical analyses of sediments collected from the bottom of the Laurentian Channel have also found evidence of these historic changes in temperature and oxygenation. The trend started well before the 20th century.</p>
<p>An analysis of deep-water chemical and physical variables also reveals a change in the relative proportions of waters from the Labrador and Gulf Stream (or North Central Atlantic) currents feeding the Laurentian Channel. The proportion of warm, less-oxygenated waters from the Gulf Stream is increasing, at the expense of colder, more oxygenated waters from the Labrador Current.</p>
<p>Therefore, a smaller contribution from the Labrador Current leads to warmer and less oxygen-rich waters. While in 1930, 72 per cent of deep water in the Laurentian Channel came from the Labrador Current, this proportion has dropped <a href="https://doi.org/10.1029/2020JC016577">to less than 20 per cent</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="graphic showing dissolved oxygen concentrations between Tadoussac and the Gulf of the St. Lawrence." src="https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=648&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=648&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469035/original/file-20220615-14-ejjivp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=648&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Distribution of dissolved oxygen concentrations (in µmol/L and per cent oxygen saturation) at the end of August 2021, from the fluvial estuary upstream from Tadoussac, to the entrance to the Gulf of the St. Lawrence. The map shows the location of the various stations visited during the oceanographic expedition.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>A global phenomenon</h2>
<p>Deoxygenation of coastal waters is a <a href="https://doi.org/10.1126/science.aam7240">phenomenon that has been observed on a global scale since the mid-20th century</a>. In 1995, approximately <a href="https://doi.org/10.1126/science.1156401">200 sites were listed</a>. By 2008, this number had more than doubled! </p>
<p>Such a large and rapid change has never been observed for an environmental variable of such great importance in coastal and estuarine marine ecosystems. In most cases, however, the lack of oxygen is temporary. When the water column is shallow and seasonally stratified, as in the Gulf of Mexico, episodes of hypoxia or even anoxia (total absence of dissolved oxygen) do not last all year.</p>
<p>Dissolved oxygen is renewed in the fall or winter, during ventilation events, where the water column is cooled by the atmosphere and the density of the surface water becomes high enough to generate a complete mixing of the water column, and carries oxygen to the bottom.</p>
<p>In the Lower St. Lawrence estuary and the gulf, hypoxia is persistent because the water column is deep and highly stratified throughout the year. The deep waters that migrate from the Atlantic to Tadoussac are isolated from the atmosphere for four to seven years and the dissolved oxygen is gradually consumed throughout the transit.</p>
<p>It remains to be seen whether the warming of the Atlantic Ocean waters will persist, thereby further threatening the ecosystems of the St. Lawrence.</p>
<p><em>Joannie Cool, who recently completed her master’s degree on oxygen dynamics in the sediments of the St. Lawrence estuary, co-authored this article.</em></p><img src="https://counter.theconversation.com/content/184626/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alfonso Mucci has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fonds de Recherche du Québec-Nature et Technologies. He is a member of the Ordre des Chimistes du Québec, the Royal Canadian Society, ACFAS, the Canadian Meteorological and Oceanographic Society, the American Geophysical Union and the Geochemical Society.</span></em></p><p class="fine-print"><em><span>Gwénaëlle Chaillou has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Fonds de Recherche du Québec, the Canada Research Chairs, and the Government of Quebec (via the Réseau Québec Maritime, MESI, MELCC). She is a member of Québec Océan, ACFAS, the Geochemical Society, and the International Association of Hydrogeologists - Canadian National Committee (IAH-CNC).
</span></em></p><p class="fine-print"><em><span>Mathilde Jutras has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fonds de recherche du Québec, fond nature et technologie (FRQNT). Mathilde is a member of the Canadian Meteorological and Oceanographic Society (CMOS) and of the Québec-Océan research group.</span></em></p>Climate change is causing the deep waters in parts of the St. Lawrence River to lose their oxygen, and it’s damaging the health of the ecosystem.Alfonso Mucci, Professeur Émérite en géochimie et océanographie, McGill UniversityGwénaëlle Chaillou, professeure de chimie marine à l'Institut des sciences de la mer de Rimouski (ISMER-UQAR), Université du Québec à Rimouski (UQAR)Mathilde Jutras, PhD candidate, physical and biogeochemical oceanography, McGill UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1831972022-05-18T12:14:45Z2022-05-18T12:14:45ZBad news for the 2022 hurricane season: The Loop Current, a fueler of monster storms, is looking a lot like it did in 2005, the year of Katrina<figure><img src="https://images.theconversation.com/files/463417/original/file-20220516-23-gs998e.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An image from satellite data shows the strong Loop Current and swirling eddies.</span> <span class="attribution"><span class="source">Christopher Henze, NASA/Ames</span></span></figcaption></figure><p>The Atlantic hurricane season starts on June 1, and the Gulf of Mexico is already <a href="https://www.ospo.noaa.gov/Products/ocean/sst/anomaly/">warmer than average</a>. Even more worrying is a current of warm tropical water that is looping unusually far into the Gulf for this time of year, with the power to turn tropical storms into monster hurricanes.</p>
<p>It’s called the <a href="https://www.aoml.noaa.gov/phod/gom/">Loop Current</a>, and it’s the 800-pound gorilla of Gulf hurricane risks. </p>
<p>When the Loop Current reaches this far north this early in the hurricane season – especially during what’s forecast to be a busy season – it can spell disaster for folks along the Northern Gulf Coast, from Texas to Florida.</p>
<p>If you look at <a href="https://images.theconversation.com/files/463461/original/file-20220516-12-acjrgz.png">temperature maps</a> of the Gulf of Mexico, you can easily spot the Loop Current. It curls up through the Yucatan Channel between Mexico and Cuba, into the Gulf of Mexico, and then swings back out through the Florida Strait south of Florida as the Florida Current, where it becomes the main contributor to the Gulf Stream. </p>
<figure class="align-center ">
<img alt="An image of the Gulf of Mexico showing how deep heat reaches." src="https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=518&fit=crop&dpr=1 600w, https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=518&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=518&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=651&fit=crop&dpr=1 754w, https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=651&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/463783/original/file-20220517-17-78u3ca.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=651&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Loop Current was about as far north as Tampa, Florida, in mid May 2022. The scale, in meters, shows the maximum depth at which temperatures were 78 F (26 C) or greater.</span>
<span class="attribution"><span class="source">Nick Shay/University of Miami</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When a tropical storm passes over the Loop Current or one of its giant eddies – large rotating pools of warm water that spin off from the current – the storm can explode in strength as it draws energy from the warm water.</p>
<p>This year, the Loop Current looks remarkably similar to the way it did in 2005, the year Hurricane Katrina crossed the Loop Current before devastating New Orleans. Of the <a href="https://www.ncei.noaa.gov/access/monitoring/monthly-report/tropical-cyclones/200513">27 named storms that year</a>, seven became major hurricanes. <a href="https://digitalcommons.odu.edu/cgi/viewcontent.cgi">Wilma</a> and <a href="https://earthobservatory.nasa.gov/images/5870/hurricane-rita-roars-through-a-warm-gulf">Rita</a> also crossed the Loop Current that year and became two of the <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/10/19/ten-years-ago-hurricane-wilma-underwent-most-extreme-intensification-in-atlantic-history/">most intense</a> Atlantic hurricanes on record.</p>
<figure class="align-center ">
<img alt="An image of the Gulf of Mexico showing how deep heat reaches in 2005, with a clear loop from west of Cuba up toward Louisiana." src="https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=518&fit=crop&dpr=1 600w, https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=518&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=518&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=651&fit=crop&dpr=1 754w, https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=651&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/463784/original/file-20220517-20215-sg6kvl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=651&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Loop Current in May 2005 looked strikingly similar to May 2022.</span>
<span class="attribution"><span class="source">Nick Shay/University of Miami</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>I have been monitoring ocean heat content for more than 30 years <a href="https://scholar.google.com/citations?user=48fm7gEAAAAJ&hl=en">as a marine scientist</a>. The conditions I see in the Gulf in May 2022 are cause for concern. The National Oceanic and Atmospheric Administration is <a href="https://www.noaa.gov/news-release/noaa-predicts-above-normal-2022-atlantic-hurricane-season">forecasting an above-average Atlantic hurricane season</a>, with 14-21 named storms, six to 10 of them hurricanes. The Loop Current has the potential to supercharge some of those storms.</p>
<h2>Why the Loop Current worries forecasters</h2>
<p>Warm ocean water doesn’t necessarily mean more tropical storms. But once tropical storms reach waters that are around 78 F (26 C) or warmer, they can strengthen into hurricanes.</p>
<p>Hurricanes <a href="https://ocean.si.edu/planet-ocean/waves-storms-tsunamis/hurricanes-typhoons-and-cyclones">draw most of their strength</a> from the top 100 feet (30 meters) of the ocean. Normally, these upper ocean waters mix, allowing warm spots to cool quickly. But the Loop Current’s subtropical water is deeper and warmer, and also saltier, than Gulf common water. These effects inhibit ocean mixing and sea surface cooling, allowing the warm current and its eddies to retain heat to great depths.</p>
<p>In mid-May 2022, satellite data showed the Loop Current had water temperatures 78 F or warmer down to about 330 feet (100 meters). By summer, that heat could extend down to around 500 feet (about 150 meters). </p>
<p>The <a href="https://theconversation.com/hurricane-ida-turned-into-a-monster-thanks-to-a-giant-warm-patch-in-the-gulf-of-mexico-heres-what-happened-167029">eddy that fueled Hurricane Ida</a> in 2021 was <a href="https://assets.bwbx.io/images/users/iqjWHBFdfxIU/ivwryYGQXVxs/v0/1200x-1.png">over 86 F</a> (30 C) at the surface and had heat down to about 590 feet (180 meters). With favorable atmospheric conditions, this deep reservoir of heat helped the storm explode almost overnight into a very powerful and dangerous Category 4 hurricane.</p>
<figure class="align-center ">
<img alt="Map of path of Hurricane Ida showing its central pressure and hurricane strength at each point and the depth of ocean heat capable of fueling a hurricane." src="https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=518&fit=crop&dpr=1 600w, https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=518&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=518&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=651&fit=crop&dpr=1 754w, https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=651&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/463419/original/file-20220516-14-62sdqg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=651&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hurricane Ida’s pressure dropped quickly as it crossed a warm, deep eddy boundary on Aug. 29, 2021.</span>
<span class="attribution"><span class="source">Nick Shay/University of Miami</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Within a storm, warm ocean water can create towering plumes of rising warm, moist air, providing high-octane fuel for hurricanes. Think about what happens when you boil a large pot of spaghetti on the stove and how the steam rises as the water gets hotter. As more moisture and heat rise within a hurricane, the pressure drops. The horizontal pressure difference from the center of the storm to its periphery subsequently causes the wind to speed up and the hurricane to become increasingly dangerous.</p>
<p>Since the Loop Current and its eddies have so much heat, they don’t significantly cool, and the pressure will continue to fall. In 2005, Hurricane Wilma had the <a href="https://www.earthobservatory.nasa.gov/images/15707/hurricane-wilma">lowest central pressure</a> on record in the Atlantic, and <a href="https://www.nhc.noaa.gov/data/tcr/AL182005_Rita.pdf">Rita</a> and <a href="https://www.weather.gov/media/publications/assessments/Katrina.pdf">Katrina</a> weren’t far behind.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/9-_obMEF_2o?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How hurricanes draw fuel from water water.</span></figcaption>
</figure>
<h2>La Niña, wind shear and other drivers of a busy season</h2>
<p>Forecasters have other clues to how the hurricane season might shape up. One is La Niña, the climate opposite of El Niño.</p>
<p><a href="https://oceanservice.noaa.gov/facts/ninonina.html">During La Niña</a>, stronger trade winds in the Pacific Ocean bring colder water to the surface, creating conditions that help push the jet stream farther north. That tends to exacerbate drought in the southern U.S. and also weaken <a href="https://www.aoml.noaa.gov/news/behind-the-2015-atlantic-hurricane-season-wind-shear-tropical-cyclones/">wind shear</a> there. Wind shear involves the change in wind speeds and wind directions with height. Too much wind shear can tear tropical storms apart. But less wind shear, courtesy of La Niña, and more moisture in the atmosphere can mean more hurricanes.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/9mKwg1oj8UM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How La Niña affects U.S.</span></figcaption>
</figure>
<p>La Niña has been unusually strong in spring 2022, though it’s possible that it <a href="https://www.climate.gov/news-features/blogs/enso/may-2022-enso-update-piece-cake">could weaken later</a> in the year, allowing more wind shear toward the end of the season. For now, the upper atmosphere is doing little that would stop a hurricane from intensifying.</p>
<p>It’s too soon to tell what will happen with the steering winds that guide tropical storms and affect where they go. Even before then, the conditions over West Africa are crucial to whether tropical storms form at all in the Atlantic. <a href="https://www.aoml.noaa.gov/saharan-air-layer/">Dust from the Sahara</a> and low humidity can both reduce the likelihood storms will form.</p>
<h2>Climate change has a role</h2>
<p>As global temperatures rise, <a href="https://www.pnas.org/doi/10.1073/pnas.2014166117">the ocean’s temperature </a> <a href="https://journals.ametsoc.org/view/journals/phoc/51/4/JPO-D-19-0295.1.xml">is increasing</a>. Much of the heat trapped by greenhouse gases that are released by human activities is <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content">stored in the oceans</a>, where it can provide additional fuel for hurricanes.</p>
<p>Studies suggest that the Atlantic is likely to see more storms <a href="https://www.pnas.org/doi/10.1073/pnas.1920849117">intensify into major hurricanes</a> as those temperatures rise, though there won’t necessarily be more storms overall. A study examined the 2020 hurricane season – which had a record 30 named storms, 12 of them hitting the U.S. – and found the storms <a href="https://www.nature.com/articles/s41467-022-29379-1.pdf">produced more rain</a> than they would have in a world without the effects of human-caused climate change.</p>
<p>Another trend we have been noticing is that the Loop Current’s warm eddies have more heat than we saw 10 to 15 years ago. Whether that’s related to global warming isn’t clear yet, but the impact of a warming trend could be devastating. </p>
<p><em>This article was updated May 24, 2022, with NOAA’s Atlantic hurricane season forecast.</em></p><img src="https://counter.theconversation.com/content/183197/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Lynn K. (Nick) Shay receives funding from the National Science Foundation and the National Oceanic and Atmospheric Administration. I am on the Board of Directors of the Integrated Ocean Observing System Gulf of Mexico Coastal Ocean Observing System Regional Association. </span></em></p>With La Niña helping clear the way for a busy hurricane season, this wide current of warm water could spell disaster for the northern Gulf Coast.Nick Shay, Professor of Oceanography, University of MiamiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/949302018-04-12T13:13:41Z2018-04-12T13:13:41ZClimate change is slowing Atlantic currents that help keep Europe warm<figure><img src="https://images.theconversation.com/files/214494/original/file-20180412-584-n22937.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Natalie Renier/Woods Hole Oceanographic Institution</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The ocean currents that help warm the Atlantic coasts of Europe and North America have significantly slowed since the 1800s and are at their weakest in 1600 years, according to new research my colleagues and I have conducted. As we’ve set out in a <a href="https://go.nature.com/2qskMM2">new study in Nature</a>, the weakening of this ocean circulation system may have begun naturally but is probably being continued by climate change related to greenhouse gas emissions.</p>
<p>This circulation is a key player in the Earth’s climate system and a large or abrupt slowdown could have global repercussions. It could cause sea levels on the US east coast to rise, alter European weather patterns or rain patterns more globally, and hurt marine wildlife.</p>
<p>We know that at the end of the last major ice age, rapid fluctuations in the circulation led to extreme climate shifts <a href="https://pubs.geoscienceworld.org/gsa/geology/article/38/4/383/130267/what-caused-the-younger-dryas-cold-event">on a global scale</a>. An exaggerated (but terrifying) example of such a sudden event was portrayed in the 2004 blockbuster film The Day After Tomorrow.</p>
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<p>The recent weakening we have found was likely driven by warming in the north Atlantic and the addition of freshwater from increased rainfall and melting ice. It has been predicted many times but, until now, just how much weakening has already occurred has largely remained a mystery. The extent of the changes we have discovered comes as a surprise to many, including myself, and points to significant changes in the future.</p>
<p>The circulation system in question is known as the “<a href="https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004RG000166">Atlantic Meridional Overturning Circulation</a>” (AMOC). The AMOC is like a giant conveyor belt of water. It transports warm, salty water to the north Atlantic where it gets very cold and sinks. Once in the deep ocean the water flows back southwards and then all around the world’s oceans. This conveyor belt is one of the most important transporters of heat in the climate system and includes the Gulf Stream, known for keeping western Europe warm.</p>
<p>Climate models have consistently predicted that the AMOC will slow down due to greenhouse gas warming and associated changes <a href="https://www.ipcc.ch/report/ar5/wg1/">in the water cycle</a>. Because of these predictions – and the possibility of abrupt climate changes – scientists have monitored the AMOC <a href="http://www.rapid.ac.uk/rapidmoc/">since 2004</a> with instruments strung out across the Atlantic at key locations. But to really test the model predictions and work out how climate change is affecting the conveyor we have needed much longer records.</p>
<h2>Looking for patterns</h2>
<p>To create these records, our research group – led by University College London’s Dr David Thornalley – used the idea that a change in the AMOC has a unique pattern of impact on the ocean. When the AMOC gets weaker, the north-eastern Atlantic Ocean cools and parts of the western Atlantic get warmer by a specific amount. We can look for this pattern in past records of ocean temperature to trace what the circulation was like in the past.</p>
<p>Another study <a href="https://www.nature.com/articles/s41586-018-0006-5">in the same issue of Nature</a>, led by researchers at the University of Potsdam in Germany, used historical observations of temperature to check the fingerprint. They found that the AMOC had reduced in strength by around 15% since 1950, pointing to the role of human-made greenhouse gas emissions as the primary cause.</p>
<p>In our paper, which also forms part of the <a href="https://www.eu-atlas.org/">EU ATLAS project</a>, we found the same fingerprint. But instead of using historical observations we used our expertise in past climate research to go back much further in time. We did this by combining known records of the remains of tiny marine creatures found in deep-sea mud. Temperature can be worked out by looking at the amounts of different species and the chemical compositions of their skeletons.</p>
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<p>We were also able to directly measure the past deep ocean current speeds by looking at the mud itself. Larger grains of mud imply faster currents, while smaller grains mean the currents were weaker. Both techniques point to a weakening of the AMOC since about 1850, again by about 15% to 20%. Importantly, the modern weakening is very different to anything seen over the last 1,600 years, pointing to a combination of natural and human drivers.</p>
<p>The difference in timing of the start of the AMOC weakening in the two studies will require more scientific attention. Despite this difference, both of the new studies raise important questions regarding whether climate models simulate the historical changes in ocean circulation, and whether we need to revisit some of our future projections.</p>
<p>However, each additional long record makes it easier to evaluate how well the models simulate this key element of the climate system. In fact, evaluating models against these long records may be a crucial step if we hope to accurately predict possible extreme AMOC events and their climate impacts.</p><img src="https://counter.theconversation.com/content/94930/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter T. Spooner receives funding from the EU ATLAS project, an international effort investigating deep-sea ecosystems and their response to ocean change (<a href="https://www.eu-atlas.org/">https://www.eu-atlas.org/</a>). </span></em></p>How we showed the Atlantic circulation system is its weakest for 1,600 years.Peter T. Spooner, Research Associate in Paleoceanography, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/694972017-07-18T14:43:26Z2017-07-18T14:43:26ZWhy deeper insights into the Agulhas Current can shed light on climate patterns<figure><img src="https://images.theconversation.com/files/178359/original/file-20170716-30889-1gazz4s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/pamilne/6127056073/">Flickr/Philip Milne</a></span></figcaption></figure><p><em>South Africa has one of the fastest and strongest flowing currents in the world running along its east coast: the Agulhas Current. It influences local as well as global rainfall and <a href="https://www.nature.com/nature/journal/v472/n7344/abs/nature09983.html">climate</a>. Katherine Hutchinson explains why it’s important to monitor a current that plays a significant role in the global ocean conveyor belt.</em></p>
<p><strong>What is the impact of the Agulhas Current on the local climate and why does it matter in the global context?</strong></p>
<p>The Agulhas Current transports warm tropical Indian Ocean water southwards along the South African coast. It modulates the rainfall along the east coast and interior regions of South Africa by providing the latent heat of evaporation needed for onshore wind systems to pick up moisture and carry it inland. </p>
<p>The current itself also sets the backdrop for local ecosystems which contribute to South African fisheries. Friction between the current and the continental shelf edge drives upwelling of nutrient rich bottom water. This in turn promotes high levels of phytoplankton – the grass of the ocean which sustains the aquatic food web. </p>
<p>The Agulhas Current also plays a critical role in global ocean circulation which is why it’s considered important for climatic conditions across the world.</p>
<p>This is due to a process known as the <a href="http://public.lanl.gov/wilbert/Research/AgulhasLeakage.html">Agulhas Leakage</a>. The current flows along the east coast of South Africa and then turns back on itself flowing into the Indian Ocean. But during this process (known as a retroflection), large pockets of warm, salty, Indian Ocean water are pinched off from the current. They form ring-like structures called Agulhas Rings or eddies which are massive spinning vortices. These eddies slowly head north-westwards, crossing the South Atlantic Ocean and eventually feed into the Gulf Stream which flows along the east coast of North America. </p>
<p>The Gulf Stream helps modulate the climate conditions of North America and Western Europe. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178103/original/file-20170713-9618-v1v0f0.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">A map of the Agulhas Current System.</span>
<span class="attribution"><span class="source">provided by author</span></span>
</figcaption>
</figure>
<p><strong>How do we know this?</strong></p>
<p>Oceanographers understand currents by measuring the changes in the ocean. But the challenge up until recently had been that the data collected on the Agulhas System only explained the current’s behaviour at a certain point in time. </p>
<p>As a result, many oceanographers have turned to computer models that simulate how ocean currents respond to other factors – like winds – which are measured by satellites. These models are not perfect, but can be very useful in providing insight into connections between different factors affecting the ocean.</p>
<p>The complex nature of the Agulhas Current has made it very difficult to simulate using ocean models. Until 2010 oceanographers were only able to observe the Agulhas Current with snapshots they got by deploying instruments during research cruises.</p>
<p>But scientific developments, combined with international collaboration, have allowed South Africa to place two long term monitoring lines across areas of the ocean where it’s believed critical exchanges of heat and salt are taking place. Heat and salt are essential parameters as they determine the buoyancy of a water mass, its tendency to sink or float. Buoyancy differences and wind forcing are the two mechanisms that drive ocean circulation. </p>
<p>To measure the oceans response to climatic changes (alterations in heat and salt fluxes and shifts in wind patterns), continuous monitoring is needed. These monitoring lines are made up of instruments placed throughout the water column. They measure current speed, direction and temperature at extremely high temporal resolutions. </p>
<p>The first array ran from 2010 to 2013 <a href="http://act.rsmas.miami.edu/">(the Agulhas Current Time-series) Experiment)</a>. This consisted of moorings placed across the Agulhas Current just off the coast of Port Elizabeth. In 2015 oceanographers replaced it with the <a href="http://asca.dirisa.org/">Agulhas System Climate Array</a>. These moorings are currently measuring the evolution of the Agulhas Current with time, providing scientists with vital information on the current’s behaviour. </p>
<p><strong>Where are the gaps?</strong></p>
<p>The ASCA array sheds a great deal of light on the behaviour of the Agulhas Current and the local implications for South Africa. But it doesn’t provide information on the amount of warm Agulhas water being leaked into the South Atlantic. This leakage is a critical link in the global ocean conveyor belt and so understanding how it is changing over time is essential in preparing for the consequences of climate change. </p>
<p>Another project was initiated in 2013 to measure the exchange of water from the Indian Ocean into the South Atlantic, the South Atlantic MOC Basin-wide Array (SAMBA). South Africa, in collaboration with France and Brazil, placed a series of instruments to capture the “corridor” of Agulhas Rings that cross the Atlantic. The aim is to monitor long term changes in inter-ocean exchange at the east and west borders of the <a href="http://onlinelibrary.wiley.com/doi/10.1002/2014EO060001/full">South Atlantic</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=331&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=331&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178240/original/file-20170714-14315-c05fln.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=331&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Depictions of the SAMBA and ASCA arrays.</span>
<span class="attribution"><span class="source">provided by author</span></span>
</figcaption>
</figure>
<p>Brazil, the United States and Argentina have deployed similar moorings on the western portion of the basin contributing to the end goal – to create a basin-wide array to bridge the entire South Atlantic. </p>
<p><strong>What do we know so far?</strong></p>
<p>South Africa is located at a major crossroad of ocean-basin exchange between the Indian and Atlantic Oceans. Several <a href="http://onlinelibrary.wiley.com/doi/10.1029/2008GL036614/full">modelling studies</a> have tried to simulate how these exchanges will alter with climate change under varying scenarios. But they have often <a href="http://journals.ametsoc.org/doi/abs/10.1175/JPO-D-13-093.1">produced</a> <a href="https://www.nature.com/nature/journal/v462/n7272/abs/nature08519.html">conflicting and inconclusive findings</a>. </p>
<p>Oceanographers previously believed that the Agulhas Current had been strengthening over time due to an increase in the Southern Hemisphere winds. But the array showed that it has been <a href="https://www.nature.com/nature/journal/v540/n7634/abs/nature19853.html">broadening</a> and not strengthening. The effects of this broadening are currently being investigated, but one outcome is that a wider current allows for a greater exchange of water between the inshore and offshore areas meaning that pollutants will more easily be shifted out to sea. </p>
<p>It’s crucial that in-situ monitoring of the Agulhas Current system continues. This kind of data will allow scientists to detect changes in the current over time. It will also help oceanographers improve their models and help them understand how variations in the current affect local and global ocean circulation and climate.</p><img src="https://counter.theconversation.com/content/69497/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katherine Hutchinson receives funding from the South African National Research Foundation under the Professional Development Programme hosted by the South African Environmental Observations Network. </span></em></p>The Agulhas Current plays a critical role in global ocean circulation that influences climatic conditions across the world.Katherine Hutchinson, PhD Candidate, South African Environmental Observations Network, and Department of Oceanography UCT, University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/716382017-02-20T20:25:40Z2017-02-20T20:25:40ZGliders are helping unlock the secrets of the Agulhas current<figure><img src="https://images.theconversation.com/files/155626/original/image-20170206-18526-171p2a.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ocean gliders are being used to study the Agulhas Current. They bring enormous benefits.</span> <span class="attribution"><span class="source">SOCCO/SAMERC</span></span></figcaption></figure><p>The Agulhas Current flows along the eastern shores of South Africa. It is one of the most powerful currents in the world, with velocities in the current often <a href="http://oceancurrents.rsmas.miami.edu/atlantic/agulhas.html">reaching 4 knots</a>. By comparison, maximum current velocities in the Benguela Jet are about 1 knot. Because of its width and depth, the Agulhas Current – like the Gulf Stream – is a major driver of the global and regional climate. </p>
<p>Understanding how the Agulhas Current varies is hugely important for other reasons too. Its interactions with coastal and shelf waters as a result of slight changes in its path or strength affect major economic activities like fishing, oil and mineral exploration and ship routing. For example, interactions between the current flow and a large swell from the Southern Ocean can lead to rogue waves, a major hazard for ships. </p>
<p>Changes in ocean circulation and water properties also have a direct impact on marine environments’ productivity, the availability of food for fish species and how and where fish move. South Africa’s coasts and shelves are home to more than 2,200 sea fish species, many endemic fish and <a href="http://www.fishthesea.co.za/swfish/species.htm">many exotic fish</a>. But this marine richness is under increasing threat from humans, particularly along the densely populated east coast. A good knowledge of ocean current conditions along South Africa’s south eastern shores is therefore essential to adequately manage the rich marine ecosystems.</p>
<p>But how the powerful Agulhas Current influences coastal regions is still poorly understood. This is because ocean currents between the Agulhas Current and the coast change rapidly in time and space. This makes them very challenging to observe. </p>
<h2>Observing the Agulhas Current</h2>
<p>Oceanic features between the Agulhas Current and the coast can’t be properly observed using traditional observing platforms. These include satellites, single ship surveys or oceanographic moorings – instruments attached along a cable anchored to the sea floor. </p>
<p>For example, in the case of the <a href="http://asca.dirisa.org/mooring-array/mooring-array-1">Agulhas System Climate Array</a> which was first deployed in 2015, each of the moorings in the array are about 25 km apart. So while the array is very useful for quantifying large scale and long-term changes in the Agulhas Current, it can’t observe the fine scale variations at the landward edge of the Agulhas Current which have a strong impact on the shelf and coast.</p>
<p>Gliders don’t have these limitations. These autonomous robotic platforms use two-way communications to relay data back to the shore in real time. Sensors on gliders measure things like pressure, temperature, salinity, ocean current and biological variables. They can provide continuous (multi-month) measurements at high spatial (100s of meters to kms) and temporal (0.5-4 hourly) resolution. </p>
<p>Gliders are cost-effective and easy to deploy. They are increasingly becoming integrated in global marine observing systems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=549&fit=crop&dpr=1 754w, https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=549&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/153636/original/image-20170120-5254-palnrm.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=549&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sea Surface temperature maps in the Agulhas Current region. Warm waters in shades of orange show the surface thermal expression of the Agulhas Current.</span>
<span class="attribution"><span class="source">CSIR-NRE</span></span>
</figcaption>
</figure>
<h2>Putting the gliders to use</h2>
<p>Gliders have been successfully used in the Southern Ocean region since <a href="http://www.soos.aq/news/current-news/163-sagliders">2012</a>. But there has been no sustained programme established around the South African coastline. </p>
<p>There have been some baby steps. Two years ago the first ocean gliders were deployed in the <a href="socco.org.za/sage/">Agulhas Current region</a>. The project was a collaboration between the <a href="https://www.csir.co.za/">Council for Scientific and Industrial Research</a>, South Africa’s central and premier scientific research and development organisation and the <a href="http://www.saeon.ac.za/">South African Environmental Observation Network</a>. </p>
<p>These <a href="http://socco.org.za/sage/index.html">first glider observations</a> showed how useful they can be. </p>
<p>For example, the gliders observed changes in and near the Agulhas Current currents happening over distances of 1-10 km. Over a period of one month, observations collected from two gliders revealed the presence of <a href="http://onlinelibrary.wiley.com/doi/10.1002/2016GL071006/abstract">small cyclonic (clockwise) eddies</a> at the edge of the Agulhas Current closest to the coast. These ocean cyclones were triggered by interactions between the Agulhas Current and the sea-bed.</p>
<p>The knock-on effect of these small cyclones was to cause intermittent currents towards the north-east – that is, against the Agulhas Current flow. Counter currents like this could help fish species in the region migrate from the southern to northern Agulhas, like the <a href="http://www.sardinerun.com/sardinerun.asp">sardine run</a> when millions of sardines travel from the Agulhas Bank to the Natal Bight in Kwazulu Natal. This usually happens between May and July. During this period the young sardines may take advantage of similar periods of north-eastward flow to progress against the Agulhas Current. </p>
<p>More high resolution observations are needed to determine how often ocean features like these small cyclones occur and to improve our understanding of their impact on the marine ecosystem. </p>
<p>Ocean science research in South Africa has historically been divided between the large scale domains – ocean basin scales – and inshore coastal domains –bays and estuaries and within a few kilometres of the shores. An ocean glider network could provide the continuous and high resolution ocean observations which are needed to connect deep ocean variability to our coastal regions.</p><img src="https://counter.theconversation.com/content/71638/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marjolaine Krug receives funding from the Council for Scientific and Industrial Research (CSIR) (YREF grant EEEO034, and PG grant EEE0023). She is affiliated with 1) the department of Oceanography, University of Cape Town, and 2) the Nansen-Tutu Center for Marine Environmental Research, University of Cape Town. She works for the CSIR Natural Resources and the Environement (CSIR-NRE) and within the Ecosystem Earth Observation group. Marjolaine Krug is a member of the GCOS-GOOS-WCRP Ocean Observations Panel for Climate and the OceanGliders Boundary Ocean Observing Network.</span></em></p>The Agulhas Current is important to South Africa for a variety of reasons. Studying how it impacts the coast has been difficult using traditional methods. But gliders are changing that.Marjolaine Krug, Senior researcher, Council for Scientific and Industrial ResearchLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/429762015-06-29T15:02:09Z2015-06-29T15:02:09ZDeclining winter sea ice near Greenland spells cooler climate for Europe<figure><img src="https://images.theconversation.com/files/86312/original/image-20150624-31495-1yuqbv4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite image showing clouds over the Greenland Sea downstream of the ice edge during conditions where there was a large transfer of heat and moisture from the ocean to the atmosphere.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>One of the most dramatic features of recent climate change is the decline of <a href="https://theconversation.com/why-arctic-melting-will-be-erratic-in-the-short-term-35969">summer Arctic sea ice</a>. The impacts of this summer ice loss on northern society, on <a href="https://theconversation.com/melting-ice-leaves-polar-ecosystems-out-in-the-sun-19807">Arctic ecosystems</a>, and the climate both <a href="http://www.nature.com/nature/journal/v464/n7293/full/nature09051.html">locally</a> and further <a href="https://theconversation.com/a-melting-arctic-and-weird-weather-the-plot-thickens-37314">afield</a>, are already being felt.</p>
<p>Less well known are the dramatic changes in winter sea ice in regions such as the Greenland and Iceland Seas, where the reduction over the past 30 years is unparalleled since 1900, when ice records in the region began. </p>
<p>In a study published in <a href="http://dx.doi.org/10.1038/nclimate2688">Nature Climate Change</a>, we show that the loss of sea ice in this subpolar region is affecting the production of dense water that forms the deepest part of the <a href="http://www.eoearth.org/view/article/150290/">Atlantic Meridional Overturning Circulation</a> (AMOC). The AMOC is an ocean circulation that carries warm water from the tropics northward in the upper layers of the Atlantic with a return flow of cold water southwards at depth. As such, the effect of these changes could mean a cooler climate in western Europe.</p>
<h2>The loss of winter sea ice</h2>
<p>Much of the dense water in the AMOC is produced in the Greenland and Iceland Seas through the transfer of heat and moisture from the ocean to the atmosphere. The heat transfer makes the surface waters in these regions colder, saltier and denser, resulting in a <a href="http://physics.info/convection/">convective overturning</a> of the water column. It also serves to warm the atmosphere in this part of the world, often resulting in distinctive cloud formations seen in satellite images of the region. </p>
<p>How much heat transfer, or atmospheric forcing, occurs depends on the magnitude of the air-sea temperature difference and the surface wind speed. As a result, it is typically largest near the sea ice edge where cold and dry polar air first comes into contact with the warm surface waters.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86448/original/image-20150625-29083-vv37s4.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">The R/V Knorr in storm conditions near Iceland where there was a large transfer of heat and moisture from the ocean to the atmosphere.</span>
<span class="attribution"><span class="source">Kjetil Våge</span></span>
</figcaption>
</figure>
<h2>Sea ice retreat and ocean convection</h2>
<p>In our study, we show that the retreat of winter sea ice has led to a large reduction in the intensity of oceanic convection in the Greenland and Iceland Seas. These changes raise the possibility of less heat being transferred from the ocean to the atmosphere in these regions, resulting in a weaker AMOC, which in turn means less subtropical water brought northwards and ultimately a possible cooling of Europe. </p>
<p>In addition to a large atmospheric forcing, oceanic convection typically occurs in regions where there is a weak vertical density contrast, usually within a closed ocean current known as a cyclonic gyre. This makes it easier for convective overturning to extend to greater depths in the ocean. Until recently, the gyres in the Greenland and Iceland Seas that are preconditioned for oceanic convection were situated close to the ice edge and, as a result, the atmospheric forcing was large, resulting in deep convective overturning. </p>
<p>However, the winter retreat of sea ice has now shifted the regions of largest atmospheric forcing away from these gyres. In other words, the regions where the forcing is largest and the regions most susceptible to deep ocean convection have moved apart. Since the 1970s, this has resulted in an approximate 20% reduction in the magnitude of this forcing, or heat transfer from the ocean to atmosphere, over the Iceland and Greenland Sea gyres.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=248&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=248&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=248&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=312&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=312&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86534/original/image-20150626-1405-qm8mba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=312&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Winter sea ice concentration (% of surface area) in the Nordic Seas during the 1960s and the 2000s. The magenta and black curves denote the regions in the Greenland and Iceland Sea where oceanic convection occurs.</span>
<span class="attribution"><span class="source">Kent Moore</span></span>
</figcaption>
</figure>
<h2>Impact on the ocean and Europe</h2>
<p>Using a mixed-layer ocean model, we have investigated the impact of this reduced atmospheric forcing. In the Greenland Sea we show that the decrease in forcing will likely result in a fundamental transition in the nature of oceanic convection there. Indeed our model results suggest a change from a state of intermediate depth convection to one in which only shallow convection occurs. </p>
<p>As the Greenland Sea provides much of the mid-depth water that fills the Nordic Seas, this transition has the potential to change the temperature and salinity characteristics of these seas. In the Iceland Sea, we demonstrate that a continued reduction in atmospheric forcing has the potential to weaken the local oceanic circulation that has recently been shown to supply a third of the dense water to the <a href="http://www.nature.com/ngeo/journal/v4/n10/full/ngeo1234.html">deep part of the AMOC</a>.</p>
<p><a href="http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2554.html">Observations, proxies, and model simulations</a> suggest that a weakening of the AMOC has recently occurred, and models predict that this slowdown will continue. Such a weakening of the AMOC would have dramatic impacts on the climate of the North Atlantic and western Europe. In particular, it would reduce the volume of warm water transported at the surface towards western Europe. This would reduce the heat source that keeps the region’s climate benign.</p>
<p>Although there is considerable debate regarding the dynamics of the AMOC, one proposed mechanism for its current and predicted decline is a freshening of the surface waters – for instance due to enhanced meltwater from the Greenland Ice Sheet. A lower salinity reduces the surface water’s density, making it more difficult for oceanic convection to occur. </p>
<p>However, much of this freshwater discharge is apt to be exported towards the equator via the <a href="https://www.whoi.edu/science/PO/pickart/Online_pubs/egc_ipy.pdf">boundary current system</a> surrounding Greenland. This limits the direct spreading into the gyres in the Greenland and Iceland Seas where oceanic convection occurs. Further work is therefore required to determine how and where – and on what timescales - this freshwater pervades the North Atlantic. </p>
<p>However, our results suggest that other possible mechanisms for a slowdown in the AMOC may be at work, such as a reduction in the magnitude of the atmospheric forcing that triggers the convective overturning in the Greenland and Iceland Seas. This process would also result in a slowdown of the AMOC, again reducing the warming that Europe experiences. Our results reinforce the idea that a warm Europe requires a cold North Atlantic, which allows for large transfers of heat and moisture from the ocean to the atmosphere. A warming North Atlantic with the associated retreat of winter sea ice therefore has the potential to result in a cooling of Europe through a slowdown of the AMOC.</p>
<p>Whether these transfers continue to decline into the future is still an open question, as is their impact on the AMOC and European climate.</p><img src="https://counter.theconversation.com/content/42976/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kent Moore receives funding from the Natural Sciences and Engineering Research Council of Canada..</span></em></p><p class="fine-print"><em><span>Ian Renfrew receives funding from the Natural Environment Research Council</span></em></p><p class="fine-print"><em><span>Kjetil Våge receives funding from the Research Council of Norway and the European Union 7th Framework Programme.</span></em></p><p class="fine-print"><em><span>Robert Pickart receives funding from the National Science Foundation.</span></em></p>Loss of sea ice near Greenland and Iceland portend a colder future for Europe.Kent Moore, Professor of Physics, University of TorontoIan Renfrew, Professor of Meteorology, University of East AngliaKjetil Våge, Research scientist in physical oceanography, University of BergenRobert Pickart, Senior Scientist in Physical Oceanography, Woods Hole Oceanographic InstitutionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/127532013-05-02T20:11:58Z2013-05-02T20:11:58ZOne flies planes, the other makes money: the two sides of aviation<figure><img src="https://images.theconversation.com/files/21898/original/qh8rn866-1364717603.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Although tightly linked to each other, airlines and the aircraft manufacturing industry don't generally seem to be heading in the same direction.</span> <span class="attribution"><span class="source">Flickr/FreeFoto</span></span></figcaption></figure><p>A few months ago I was invited to a small gathering organised by executives from a large international airline (one you most certainly have heard of). About a dozen of us were there and the mix was varied: reps from CASA, Airservices Australia, Sydney airport, various banks and so on. The airline wanted to discuss parts of their strategic plan and a lively discussion ensued.</p>
<p>Before the presentation took place, I had a chat with some of the people around the room and I came across this banker who seemed particularly agitated. “This is my first one of these,” I say. “What should I expect?”. He replies with: “Well, you never know with these airlines. I still don’t know how they manage to stay in business after all these years without making any MONEY!” </p>
<p>Truth is, the airline that organised the gathering was doing quite well but most would agree with him - airlines don’t have the best record as profit-making organisations. Just last March, <a href="http://video.cnbc.com/gallery/?video=3000151858">Warren Buffett claimed</a> that the airline industry has “all the ingredients of a bad business”.</p>
<p>However, although the companies that are flying passengers from A to B (i.e. the airlines) don’t always do well financially, the large corporations selling them the planes (i.e. the aircraft manufacturers) are for the most part showing healthy numbers. There is clearly a discrepancy between the aircraft buyers (or leasers) and the aircraft makers - but why? How come these two inter-linked industries seem to fare so differently?</p>
<h2>Aircraft orders taking off</h2>
<p>The commercial aerospace industry can be broken down into two main components: the companies that make the aircraft - commonly referred as the OEM (Originial Equipment Manufacturer); and the airlines (the customers acquiring the planes). Most people could name at least two OEMs: <a href="http://en.wikipedia.org/wiki/Boeing">The Boeing Company</a> and <a href="http://en.wikipedia.org/wiki/Airbus">Airbus</a> (which is a subsidiary of <a href="http://en.wikipedia.org/wiki/EADS">EADS</a>). Other OEMs include <a href="http://en.wikipedia.org/wiki/Bombardier_Aerospace">Bombardier Aerospace</a>, <a href="http://en.wikipedia.org/wiki/Embraer">Embraer</a>, <a href="http://en.wikipedia.org/wiki/Gulf_Stream">Gulf Stream</a> and many others. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/19372/original/jzq8m3vx-1358483517.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Boeing 787 being assembled.</span>
<span class="attribution"><span class="source">Boeing</span></span>
</figcaption>
</figure>
<p>Boeing and Airbus have both broken several industry records in the last couple of years in terms of aircraft orders. Last year, Boeing took the largest commercial aviation order in its history for the <a href="http://www.bloomberg.com/news/2012-02-14/boeing-signs-record-order-from-lion-air-for-737-airplanes.html">delivery of 230 planes</a> worth a combined A$22.4 billion to Indonesian carrier Lion Air. Also last year, <a href="http://www.ft.com/intl/cms/s/0/bf624d78-47a2-11e1-9a92-00144feabdc0.html#axzz2PwyXeT3K">Southwest Airlines placed an order</a> for 208 single-aisle Boeing aircraft worth $19 billion while Norwegian Air Shuttle purchased 122 Boeing 737 aircraft for around A$11 billion. More recently, Airbus landed a <a href="http://www.news.com.au/business/breaking-news/airbus-orders-200-jets/story-e6frfkur-1226599534784">massive order from Lion Air</a> worth A$18 billion for 234 A320 jets. Airbus has even said it may have to ask for <a href="http://www.bloomberg.com/news/2013-04-08/airbus-juggles-order-book-to-meet-record-demand-for-a320neo-jet.html">increased flexibility</a> from its customers to cope with the incoming orders aiming for <a href="http://au.news.yahoo.com/world/a/-/world/16636053/airbus-sales-chief-aims-to-hit-750-plane-orders-in-2013/">750 plane orders in 2013</a>.</p>
<p>These large OEMs are also strengthening their position by absorbing some of the maintenance work previously done by maintenance repair and overhaul companies (commonly referred to as MROs). These companies are also struggling as the amount of aircraft maintenance work required is decreasing due to new technological advances, (including advanced materials, as previously <a href="https://theconversation.com/lets-stick-together-composite-materials-aeroplanes-and-you-7207">discussed in The Conversation</a>).</p>
<p>Some of the large OEMs have another advantage: their military portfolio. Defence projects are immensely important to many of the OEMs’ bottom line and some of the resulting project outcomes do eventually <a href="https://theconversation.com/military-backed-research-is-being-cut-back-but-will-this-affect-science-4890">trickle down to commercial aviation</a>. However, military budgets are being tightened as shown by flat defence revenues <a href="http://deloitte.wsj.com/cfo/2013/02/14/2013-outlook-on-aerospace-defense/">through the first nine months of 2012</a> at the global level, and global economic challenges in the near future will likely result in <a href="http://www.reuters.com/article/2012/11/07/us-boeing-defense-restructuring-idUSBRE8A61Z320121107">additional decreases in revenue</a>.</p>
<p>OEMs are also consolidating their place in the market by strengthening their position through mergers. Over the past 20 years, over <a href="http://www.imaa-institute.org/statistics-mergers-acquisitions.html#M&A_Ind_Aerospace&Defense">6000 mergers and acquisitions</a> totalling a value of more than A$600 billion took place worldwide. Airlines are experiencing <a href="https://theconversation.com/the-qantas-emirates-alliance-a-flight-path-to-future-growth-9363">a similar phenomenon</a> by merging or forging alliances as best shown by last month’s ACCC approval for the <a href="https://theconversation.com/accc-approves-qantas-emirates-deal-the-experts-respond-13117">Qantas-Emirates partnership</a> and Virgin Australia’s move to <a href="http://www.news.com.au/business/companies/accc-approves-virgins-tiger-acquisition/story-fnda1bsz-1226626858789">acquire a majority stake</a> in Tiger Airways. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/21899/original/2txqddhx-1364719673.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">The number of airlines has skyrocketed in the US and Europe since deregulation in the 1990s.</span>
<span class="attribution"><span class="source">Flickr/MomentsForZen</span></span>
</figcaption>
</figure>
<h2>A battle between legacy airlines and new emerging players</h2>
<p>The aviation industry is notoriously difficult with large capital and operating costs, high fuel costs and increasing competition at a global scale. In Australia, it is also particularly exposed to the rising dollar.</p>
<p>The memories of the Ansett’s agony to bankruptcy are still in most people’s mind although one does not need to look that far back, as shown by last year’s <a href="https://theconversation.com/qantas-cuts-jobs-air-australia-collapses-how-can-we-save-our-airlines-5435">Air Australia collapse</a>.</p>
<p>Looking at the latest half-yearly results, Qantas showed a <a href="http://blogs.crikey.com.au/planetalking/2013/02/21/flash-qantas-posts-improved-half-year-results/">statutory profit of A$111 million</a> for the six months ending in December 2012 but it suffered a 34% fall in earnings from domestic business travel with Virgin Australia increasingly competing in the corporate travel sector. Virgin Australia is also hurting with a net profit that <a href="http://www.businessspectator.com.au/news/2013/2/26/resources-and-energy/virgin-australia-hit-first-half-profit-slump">decreased by half to A$23 million</a> according to the latest half-yearly numbers. </p>
<p>On the international front, Qantas International reported a loss of A$91 million, although it will be interesting to see how the Qantas-Emirates partnership will impact Qantas International earnings in the years to come. But with both airlines ramping up capacity on domestic travel - in attempt to eat into the competition’s market share - the supply is exceeding demand and flying empty seats may result in future losses.</p>
<p>Airlines operating in Australia are hardly the only ones facing challenges. The collapses of long-established carriers such as <a href="http://www.bbc.co.uk/news/business-16787761">Spain’s Spanair</a> and <a href="http://aviationblog.dallasnews.com/2013/03/amr-american-airlines-ask-bankruptcy-judge-for-more-time-to-file-a-plan-of-reorganization.html/">American Airlines</a> underscore the grim financial reality the industry faces. In the past nine years, airlines as a whole suffered an <a href="http://www.bangkokpost.com/learning/learning-from-news/279650/global-airline-industry-unprofitable">aggregate loss of US$47.9 billion</a>.</p>
<p>However, Berkeley economist and commercial aviation expert <a href="http://facultybio.haas.berkeley.edu/faculty-list/borenstein-severin">Severin Borenstein</a> believes that high taxes and fuel costs play a minor role in airline operations. The major drivers are related to fluctuations in demand, government policy and the large cost differential between legacy airlines and new low-cost carriers. </p>
<p>These low-cost airlines are strengthening their position in the market as shown by <a href="http://www.guardian.co.uk/business/2013/mar/19/ryanair-175-new-planes-boeing">Ryanair’s recent order for 175 new Boeing planes</a>. Legacy airlines have responded accordingly and the difference in price and service between legacy airlines and low cost carriers is becoming <a href="http://www.economist.com/blogs/gulliver/2013/03/legacy-vs-low-cost-carriers">increasingly narrow</a>. </p>
<p>Demand to use airways has been steadily increasing since the 1970s an the rapid growth in Asia will translate into demand for thousands of new aircraft over the next decades as <a href="http://airinsight.com/2012/09/25/comparing-the-oem-aircraft-market-forecasts/">forecasts</a> by both Airbus and Boeing show. </p>
<p>While airlines in “legacy markets” are struggling to beat an increasing competition, the OEMs are indeed adapting to new market movements by servicing customers from emerging markets.</p><img src="https://counter.theconversation.com/content/12753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hamza Bendemra 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>A few months ago I was invited to a small gathering organised by executives from a large international airline (one you most certainly have heard of). About a dozen of us were there and the mix was varied…Hamza Bendemra, Doctoral Candidate, Engineering, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.