West Antarctic ice loss overestimated by NASA sats
Incorrect allowance made for trampoline-like bedrock
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Scientists using a network of ground sensors emplaced in Antarctica say that NASA satellites have overestimated the amount of ice that is melting and running off into the ocean from the polar continent.
The new results come from the West Antarctic GPS Network (WAGN), which uses 18 locator stations "bolted to bedrock outcrops" in the Western antarctic to discover "ground truth" regarding the phenomenon of "postglacial rebound", where the bedrock lifts as the mile-thick ice sheet atop it diminishes.
Postglacial rebound is important, as NASA's Gravity Recovery and Climate Experiment (GRACE) satellites estimate ice loss by measuring regional gravitational forces as they fly overhead. Both ice loss and bedrock rebound contribute to GRACE grav-scan readings, and according to the WAGN measurements, rebound figures used to estimate ice loss have now been shown to be wrong.
"The take home message is that Antarctica is contributing to rising sea levels. It is the rate that is unclear," says Ian Dalziel, lead investigator for WAGN.
The WAGN boffins say they are sure that recent figures for ice loss calculated from GRACE readings have been overestimated, but they are not yet sure by how much. However, they say that there is no dispute about the fact that ice is disappearing from the antarctic sheet - this process has been underway for 20,000 years, since the thickness peaked during the last "glacial maximum".
"The published results are very important because they provide precise, ground-truth GPS observations of the actual rebound of the continent," said Vladimir Papitashvili of the Antarctic Earth Sciences Program at the National Science Foundation, which supported the research.
The results are given in the paper Geodetic Measurements of Vertical Crustal Velocity in West Antarctica and the Implications for Ice Mass Balance, published here in the journal Geochemistry, Geophysics, Geosystems (subscriber link). There's also some layman-level exposition from Texas uni here. ®
COMMENTS
@callmezeke
At last someone who talks sense.
I think given your viewpoint it seems that every news article is skewed (I mean one's viewpoint, but that sounds a bit posh). I believe in anthropomorphic climate change, but I can be convinced either way - I just don't want to take the risk. From my viewpoint The Register seems biased (and I don't get the argument that they're trying to cause balance because The Reg isn't read by the general population and the best way to get balance is to be balanced). From a sceptic viewpoint the output of, for example, The Independent must seem pretty off the wall.
The problem is that news agencies on both sides are picking individual articles from the thousands and hanging the entire debate on a single source. It's like walking across a road and either banning cars or removing zebra crossings based on the safety of that one crossing.
So can everyone stop trying to prove or disprove climate change and its causes using individual pieces of evidence?
@devon
East Antarctica is four times the area of West Antarctica, and the ice cap is deepest (even over the underlying rock) near the pole. Much of West Antarctica comprises the major ice shelves (Ross, Ronne, and Larson, the latter of which is experiencing the most dramatic reduction). Ice shelves already displace their mass in the water, though (meaning any melt from those doesn't raise the sea level).
The journal 'Science' cites the East as gaining 45 +/- 7 gigatons of ice per year.
Just two of many sources of additional info:
http://www.sciencemag.org/cgi/content/abstract/1110662
http://www.news.com.au/story/0,27574,25348657-401,00.html
Note, please, that I'm not denying that West Antarctica is warming and melting. But there's more to the situation down there than just the West, and the major news outlets' consistent omission of East Antarctic conditions skews viewers' and readers' perceptions.
@callmezeke
Stop muddying the water.
You must know that the West is where all the ice is and the East is largely above sea level and made of rock. The East does have a very small amount of increase, but the West is losing 50 gigatonnes of ice per year. Have a look at Rignot et al. in Nature Geoscience.
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