If they were hoping to see a steady rate of change that matched carbon dioxide emission levels, they were disappointed. Natural variations inconveniently got in the way, two in particular: ‘When two extreme snowfall events in 2009 and 2011 dropped around 600 gigatons of snow and ice, the East Antarctic Ice Sheet thickened so much that it temporarily halted the entire continent’s ice losses, said Wang—a pattern that had previously escaped notice.’
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A new analysis of long-term satellite records shows the East Antarctic Ice Sheet is unexpectedly dependent on fluctuations in weather.
This study may improve models of how much sea levels will rise, says Eos News.
As more coastal communities face the looming threat [Talkshop note: unsupported assertion] of rising sea levels, it’s more important than ever to accurately predict changes in one of the greatest potential sources of sea level rise—the melting of Antarctica’s massive ice sheet.
Recently, scientists analyzed nearly 2 decades’ worth of data from sensitive NASA satellites documenting mass changes in the Antarctic Ice Sheet.
They found the ice inventory ebbed and flowed across the continent in unexpectedly variable patterns.
Traditionally, some groups of Antarctic researchers have assumed the rate of change across the ice sheet is constant, but they drew their conclusions from data sets that spanned only a few years, said Lei Wang, a geodesist at The Ohio State University who will present this research at AGU’s virtual Fall Meeting 2020.
“These long data records give us the capability to characterize the ice sheet’s variation over a range of timescales,” rather than just modeling seasonal variations and short-term trends, Wang said.
Understanding Long-Term Trends
The Antarctic Ice Sheet, the largest mass of ice on Earth, is divided into two unequal portions, with the East Antarctic Ice Sheet covering about two thirds of the continent. The West Antarctic Ice Sheet, although smaller, has historically been more closely studied because it’s melting faster. (The East Antarctic Ice Sheet sits on bedrock above sea level, said Wang, so it is less susceptible to the effects of the warming ocean.) NASA estimates Antarctica has lost 149 billion metric tons of ice per year since 2002.
When so much ice is involved, projections of how sea levels will respond are uncertain—especially when trends already are so difficult to gauge.
Indeed, the field still argues about sea level changes in the past century, said Jim Davis, the study coauthor and a geodesist at the Lamont-Doherty Earth Observatory at Columbia University. “We’ve got to get to the point where we can talk about what’s happening this year in sea level change,” he said.
To do that, researchers need a more sophisticated model of how Antarctica’s shield of ice is evolving.
Full article here.
via Tallbloke’s Talkshop
December 7, 2020 at 07:39AM