The melt rate in Greenland and Antarctica


in Geek stuff, Politics, Rants, Science, The environment

The latest issue of Nature Geoscience features an article by David Bromwich and Julien Nicolas, in which they produce an estimate of the rate at which the Antarctic and Greenland ice sheets are melting in response to climate change. Their estimate is based on satellite gravimetry using the Gravity Recovery and Climate Experiment (GRACE) mission (mentioned before). They concluded that previous estimates hadn’t properly taken into account the phenomenon of isostatic rebound and that, as a consequence, the rate of ice loss is about half what was estimated before:

With glacial isostatic adjustment modelled in, the loss from Greenland is put at 104 gigatonnes, plus or minus 23 gigatonnes, and 64 gigatonnes from West Antarctica, plus or minus 32 gigatonnes.

On the basis of this, they concluded that icesheet loss accounts for about 30% of observed sea level rise, rather than the 50% estimated before. The remainder is the result of the oceans expanding as they warm up.

Inevitably, the reduced ice melt estimates will be jumped upon by climate change delayers and deniers. This once again re-enforces the asymmetry in the debate between scientists and those who argue for inaction on climate. The latter never admit their mistakes but jump on any correction, error, or update from scientists as proof that climate science is deeply uncertain, and that no action should be taken now.

{ 5 comments… read them below or add one }

R.K. September 10, 2010 at 12:55 pm

Regardless of how deniers will use this information, it is still good news. It suggests we have more time to sort out the problem, which is just what we need given how inactive governments have been.

. April 21, 2011 at 9:23 pm

Melt from Arctic glaciers would nearly fill Lake Erie, study says
Ice loss contributes to rise in sea level
Margaret Munro, Postmedia News

Over the six years Alex Gardner monitored Canada’s Arctic glaciers and ice caps, he says they lost almost as much water as there is in Lake Erie.

The ice loss has increased sharply “in direct response to warmer summer temperatures” since 2004 -so sharply that Gardner and his colleagues say the Canadian Arctic Archipelago was the single largest contributor to global sea-level rise outside Greenland and Antarctica between 2007 and 2009.

“Even though these Canadian glaciers and ice caps are small compared to the huge ice sheets, they play a significant role in sea level rise,” says Gardner.

Peer reviewed science! July 14, 2011 at 10:36 pm

Tripati, A. K., C. D. Roberts and R. A. Eagle. 2009. Coupling of CO2 and ice sheet stability over major climate transitions of the last 20 million years. Science December 4. Vol 326 No. 5958, pp 1394-1397, doi:10.1126/science.1178296.

Recent study finds that the close coupling between CO2 and climate extends through major climate transitions of the past 20 million years and that CO2 levels have not been as high as present (387 ppmv) since the Mid-Miocene (~15 million years ago).

Tripati et al. employ a technique based on the ratio of boron (B) to calcium (Ca) in foraminifera (single celled marine algae) from sites in the western tropical Pacific Ocean to study CO2 levels during the major climate transitions of the last 20 million years. Over the past 800, 000 years, their results coincide with atmospheric CO2 concentrations derived from Antarctic ice cores showing concentrations ranged between ~180 ppmv and ~280 ppmv prior to the industrial revolution. The only period when CO2 levels approached modern levels was during the Early and Mid-Miocene (~20-14 million years ago; Ma) when concentrations were sustained at ~400 ppmv. Climate proxies indicate that global temperatures during the Middle Miocene were ~3-6oC warmer and sea level 25-40 m higher than today. Decreases in CO2 were coincident with major episodes of glacial expansion documented in other climate proxies. For example, the B/Ca record indicates that CO2 dropped by ~200 ppmv over the period ~14-10 million years ago and by ~150 ppmv during the late Pliocene (~3.3-2.4 Ma). The results indicate that changes in CO2 were closely related to the climate evolution of the Middle and Late Miocene and the Late Pliocene and therefore likely played an important role in driving these transitions.

Summary courtesy of Environment Canada

. August 26, 2012 at 12:58 pm

The land masses that encircle the Arctic also prevent the polar oceans revolving around it as they do around Antarctica. Instead they surge, north-south, between the Arctic land masses in a gigantic exchange of cold and warm water: the Pacific pours through the Bering Strait, between Siberia and Alaska, and the Atlantic through the Fram Strait, between Greenland and Norway’s Svalbard archipelago.

That keeps the average annual temperature for the high Arctic (the northernmost fringes of land and the sea beyond) at a relatively sultry -15°C; much of the rest is close to melting-point for much of the year. Even modest warming can therefore have a dramatic effect on the region’s ecosystems. The Antarctic is also warming, but with an average annual temperature of -57°C it will take more than a few hot summers for this to become obvious.

. April 2, 2016 at 1:38 pm

The Danger of a Runaway Antarctica

If carbon dioxide emissions from fossil fuels continue unabated, the vast West Antarctic ice sheet could begin to disintegrate, causing the sea to rise by five to six feet by the end of the century, destroying coastal cities and low-lying island nations and creating environmental devastation within the lifetimes of children born today.

The startling new finding was published Wednesday in the journal Nature by two experts in ice-sheet behavior: Robert DeConto of the University of Massachusetts, Amherst, and David Pollard of Pennsylvania State University. It paints a grimmer picture than the one presented only three years ago by a United Nations panel that forecast a maximum sea level rise of three feet by 2100. But that projection assumed only a minimal contribution from the massive ice sheets of Greenland and Antarctica. And things could get worse in the centuries to come — the melting from Antarctica alone, not counting other factors like thermal expansion, could cause the seas to rise by nearly 50 feet by 2500, drowning many cities.

But the report also contains what passes for good news nowadays: The collapse of Antarctica is not inevitable, it says, and could be prevented with an aggressive global effort to keep greenhouse gases at or below the levels called for in Paris, where leaders embraced a goal of holding warming “well below” an increase of two degrees Celsius compared with preindustrial levels.

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