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Melting ice the greatest factor in rising sea levels

Melting glaciers and ice sheets have contributed more to rising sea levels in the past decade than expansion from warming…

Scientists have a better understanding of the contribution of melting glacier and ice sheets to sea level rise, but much remains uncertain. Flickr/ChrisGoldNY

Melting glaciers and ice sheets have contributed more to rising sea levels in the past decade than expansion from warming water, according to modelling in the latest report by the Antarctic Climate and Ecosystems (ACE) Cooperative Research Centre.

Before 2000 thermal expansion was the biggest factor in rising sea levels.

The shift was “a fairly sure sign that you’re getting out of the normal balance”, said report author Dr John Hunter, an oceanographer and expert in rising sea levels at the ACE.

Report Card: Sea Level Rise 2012 provides a summary of the past decade of peer-reviewed scientific research into sea-level rise, and is the most recent update since a report in 2008.

During the 20th century sea levels rose at a rate unmatched for 6,000 years, the report says. Satellite measurements have confirmed the global average rise of 1.9mm a year, as measured in tide gauges. “This present sea-level rise is due to a combination of thermal expansion of a warming ocean and the melting of glaciers and ice sheets.”

Dr Hunter explained that modelling had improved since the last update, at which time the contribution to sea levels from melting glaciers and ice sheets was not well understood.

“We’ve been better able to match up two things: observed sea level rises - which we get by looking at tide gauges until about 20 years ago, then after that tide gauges and also records from satellites - and estimates of sea level rises, which we get by looking at ocean temperatures and observing ice on land, the two biggest components, among other things,” Dr Hunter said.

“If we can get those estimates to agree with the observations from tide gauges and satellites, then we have a good understanding of sea level rise. At the time of the last assessment, that wasn’t all that well done, and we didn’t know very much about ice. We’ve got a better understanding now.”

But estimating the future rate of ice loss from the Greenland and Antarctic ice sheets remained the largest uncertainty in projecting sea-level rise over the next century, he said.

From 1993 to 2009, reconstructed tide-gauge data shows a rise of 2.8mm per year and satellite data shows a rise of 3.2mm per year.

Since 1972, thermal expansion contributed about 45% to total sea level rise, glaciers and ice caps another 40%, with most of the remainder from the ice sheets, the report says. Since 1993 the contribution of the ice sheets to sea-level rise has increased to about 30%.

The Intergovernmental Panel on Climate Change has estimated that projected sea level rise over the next century could vary from about 10-20cm to about 80cm.

Dr Hunter said it was “only just about now that we’re starting to observe melting from ice is starting to overtake thermal expansion. If you disturb the earth, the first thing that happens is that you just get thermal expansion from the heating of the water, and there’s quite a lag before melting from the ice starts to kick in, and eventually the ice becomes a greater contributor. This is always a fairly sure sign that you’re getting out of the normal balance.”

The two biggest impacts of the rising sea level will be flooding from inundation along hard shoreline, and coastal recession along soft shoreline, the report says. A relatively modest increase in mean sea level of 50cm will increase the frequency of flooding by a factor of roughly 300.

“In Australia we’re reasonably lucky in that the projections for inundation are pretty close to the global average,” Dr Hunter said, meaning sea level would be around 38cm higher in 2090 than in 1990. “On the east coast, where the water is warmer, the rise will be slightly greater than on the west coast - by 10cm to 20cm - by the end of the century.”

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24 Comments sorted by

  1. Greg MacDonald

    logged in via Facebook

    Me thinks we need to look at a few ways to mitigate this impending disaster. One of the cheapest and possibly ameliorative ways would be to purposely flood those area of planet earth that are below sea level. The Caspian Sea is an obvious choice and could handle quite an enormous quantity of water. The Quatar Depression and Death Valley could equally handle significant quantities of water and if we flooded these areas by using the water flow to generate electricity and managed the new salt water lakes to generate rainfall in very dry area it might just be a win/win/win scenario that could give us a few extra years to figure something out before it is too late.

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    1. David Arthur

      resistance gnome

      In reply to Greg MacDonald

      If it's that good an idea, let's also flood the Eyre Basin. If we in Australia have objections to that on environmental grounds, perhaps we could expect the same of Central Asians, Jordanians and Israelis, Californians and Qataris.

      A few extra years of planning time are irrelevant, we've already had plenty of such years - most of which has been blocked by the Denialist movement.

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    2. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to Greg MacDonald

      Yes, Greg, I like the way you think . . . more surface area generally, being heated will evaporate more water vapour.

      The real trick will be to find mountains to leeward . . .

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  2. Diana Brown

    Parent; language student

    Methinks 6000 years is not a very long time in geological/cosmic terms, no?

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  3. Bernie Masters

    environmental consultant at FIA Technology Pty Ltd, B K Masters and Associates

    Just in the last 2 or 3 weeks, New Scientist has reported on a study which showed that 43% of sea level rise over the last few decades has been caused by the pumping of freshwater aquifers and discharge of the water (once used) into our oceans. I'd be interested in having the CSIRO comment on this news and factor it in to their equation.

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    1. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to Bernie Masters

      Well yes, of course. I've written myself not just here but elsewhere of this propensity to allow water to simply run off into the oceans, not only from aquifers but precipitation as well.

      The perpetual excuse given is that for some reason, cultural, or delusional, or whatever, unless a stream is actually flowing then it must be 'unhealthy'.

      No thought of from where the water is flowing, and to where, or how little time it takes to get there.

      But don't despair. We all know that the most widespread…

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    2. Gary Murphy

      Independent Thinker

      In reply to Bernie Masters

      Extra heat will cause more cloud formation.

      More evaporation as a result of higher temperatures - not more surface area.

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    3. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to Bernie Masters

      Sorry, good thing I check back occasionally. Gary, please explain, more heat will cause of cloud formation, of what exactly?

      Heat doesn't cause clouds to form, of anything. All heat does is make things hot, producing fewer clouds not more. Clouds to which I refer form from condensation of water vapour, from high relative humidity in a warm layer running up into a cold layer.

      Cold causes cloud formation. Clouds don't form over arid lands and deserts but over high mountains where incoming air…

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    4. Gary Murphy

      Independent Thinker

      In reply to Bernie Masters

      Seriously?

      More heat IN THE OCEANS causes more water molecules to exceed the liquid / gas phase boundary and evaporate.

      That is why they get more rain in the tropics.

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    5. Alex Cannara

      logged in via Facebook

      In reply to Bernie Masters

      "Heat doesn't cause clouds to form" -- so you never had science in grammar school, or anywhere else? The condensed steam coming out of a tea kettle doesn't come out because you turned the heat on underneath? Really?

      For others here, the rising sea temps means more clouds, more water vapor in the air, more absorption of the many IR energy bands water vapor loves, and so more warming. This is a self-fuelling, positive-feedback effect, much like driving backwards and letting go of the steering wheel.

      Water vapor requires 628 Watt Hours to make from each pound of water boiled away. So clouds indeed help compensate somewhat for higher sea temps by delivering that heat higher in the atmosphere so that some of that 628 WH per lb can more easily escape to space when the cloud's droplets or snowflakes form.

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  4. Alex Cannara

    logged in via Facebook

    Whatever mitigation is attempted, consider the reality of just trying to refreeze the >50 cubic miles of ice now melting off Greenland each year -- all the power generated by all plant sin all countries running freezing gear for several years would do just one year of refreezing at 0C. Each year that all humanity ised no power for itslef could at best fall at least 3 years behind Greenland;s melt.

    Of course, Greenland's melt is doubling about every 8 years. Too bad our scientists & engineers had thought about, and solved, global CO2 emissions problems in 1962 (http://tinyurl.com/6xgpkfa), but our childish politics failed us, as usual (http://tinyurl.com/73p7ler).

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  5. Arthur James Egleton Robey

    Industrial Electrician

    I came here expecting to be amused by Climate Catastrophe deniers.
    How disappointing.

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    1. Bill Price

      logged in via Facebook

      In reply to Arthur James Egleton Robey

      Mr. Robey and Mr. Cannara,

      I've been asking questions about SLR since 1997, when on the Carteret County Beach Preservation Task Force,,, and, so far, haven't gotten a dime from anyone. (Certainly not the best paid.)
      Maybe that's why I'm not very amusing.
      Of course, when scientists propose to take the property rights of local property owners that have tended their land and paid taxes , in some cases, for generations, I don't think the taxpayers would think anything about it is as amusing as…

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    2. Alex Cannara

      logged in via Facebook

      In reply to Arthur James Egleton Robey

      Not sure what you want, Bill. I dave you the refs to sea rise observations and projections. What's always a pain to those warning folks is that some folks do have $ in the deal and so fight reality, thus adding costs others will have to pay later.

      New Orleans & Katrina was a clearly warned-of tragedy some years earlier in Scientific American. Anybody in the state or fed govts. act on those very well -established scientific warnings?

      NC establishing a linear-forever sea rise behavior is…

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  6. Bill Price

    logged in via Facebook

    Why not compare 1850's US Coast Survey surveys, with current surveys to see how much inundation has occured in 160 years.
    ( Of course you would have to exclude erosion / accretion due to Wind, Waves, Currents, Dredging , but rapid inundation of Tidelands should be relatively easy to see.)
    Bill Price Pine Knoll Shores NC

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    1. Bill Price

      logged in via Facebook

      In reply to Bill Price

      Please see below,,
      I didn't see the Reply tab.
      Bill Price

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  7. Bill Price

    logged in via Facebook

    Mr. Cannara,

    Yes, the US Coast Survey surveys from 1850's are available in the Library of Congress . ( I have an original of 1855.)

    However, what I am asking for is a Comparative Survey of 1850's surveys with today, to see how much Inundation has occurred.

    The NC CRC Science Panel said 2' of SLR has occurred for the NC Coast since 1850's, and Dr. Pilky says 1 ' of SLR = up to 2 miles of inundation, which would result in inundation of 4 miles for tideland NC, so it should be easy to see.
    The CRC SP has ignored a written request to see a comparative survey since February 2011.
    We asked a NC Educational Institution if a comparative survey existed , if not , do one. They declined, and then invited Ramsdorff to a gala private SLR Promotion Planning meeting.

    After such dismissive actions by the Green Intelligencia, somehow, I don't think I would have much confidence in any report done by either of the above.

    Bill Price

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    1. Alex Cannara

      logged in via Facebook

      In reply to Bill Price

      Bill, I understand VA, NC or SC legislature has done something to legislate a linear sea rise increase for the purposes of planning =-- pretty amazing that such people get elected!

      Here's a ref or two...
      http://flood.firetree.net/ http://www.csc.noaa.gov/digitalcoast/tools/slrviewer
      www.miamiherald.com/2012/03/13/2691984/florida-at-highest-risk-for-flooding.html
      www.bcdc.ca.gov/planning/climate_change/SLRfactSheet.shtml

      Out in Calif, we have the BCDC which is tasked with estimating sea rise effects, since they eill be exceedingly expensive around San Francisco Bay.

      Wonder if the deniers are adding tio their trust funds so they can pay everyone back when it becomes clear how idiotically self interested they were?
      ;]

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    2. Bill Price

      logged in via Facebook

      In reply to Bill Price

      Regarding NC Sea Level Rise Law

      NC Lawmakers base Laws on Facts, not Fiction, or Comedy.
      CRC’s Scientists have declined to answer questions on their Science Report since Feb,2011. Why?
      One CRC Scientist said, in effect, that it was better to be fast and cheap,, than accurate. (Can you believe that?)
      NC Lawmakers disagreed. They want to be accurate. 

      Bill Price Pine Knoll Shores

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    3. Alex Cannara

      logged in via Facebook

      In reply to Bill Price

      Why is it that when one scientists says something that supports an opinion against the science, it gets repeated. But, when thousands, hundreds or tens of scientists say something that doesn't support the anti-science position, all those voices are ignored?
      ;]

      So if NC chose the linear sea rise model for their compensation to flood victims, that will be viewed as "responsible" by our offspring when rise accelerates? It's never going to be less than linear in hundreds of years, so I wonder why the lawmakers chose a fixed compensation rate, rather than a real, actual one? Hmmmm

      Maybe they'll ask us all, via the feds, to make up the difference, if necessary? Silly me.

      "They want to be accurate" -- if true, they'd leave it open to following observations, which are indeed beginning to accelerate. I guess we in Calif. just don't get how to do it the NC "accurate" way, eh?

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    4. Bill Price

      logged in via Facebook

      In reply to Bill Price

      In medieval times, 100% of social, governmental, and the religious leaders were 100% certain Galileo was wrong. Turned out 1 guy was right and everyone else was wrong,, so group think doesn't necessarily make it right, no matter how many PhD's are piled up. ( In fact, remember in the 70's , most all the PhD's were certain on Global Cooling.)

      I think what happened in NC is that the Scientists wouldn't answer questions about their Hindsight, and, as nobody in omniscient, the GA began to question…

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    5. Alex Cannara

      logged in via Facebook

      In reply to Bill Price

      Bill, you're simplifying things too much. Galileo was preceded by Copernicus, and Arabic scientists. Dealing with the Papal state, Galileo was initially accepted as bringing knowledge of the world to the church. Then, some church bureaucrats, ever protective of position & influence, realized the logical threat to church doctrine, should what Galileo (and others) wrote get out to the general populace, upon whom all church revenue & influence depended.

      Thus, the attacks from within the church…

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