Dec 03, 2014
The rate of melting ice in Antarctica's vulnerable Amundsen Sea region has tripled in the past decade, a new report published in Geophysical Research Letters on Wednesday has found.
Analyzing 21 years of data from four separate observation techniques, scientists from NASA and UC Irvine (UCI) discovered that glaciers in the region are shedding more ice mass than any other part of Antarctica and are the biggest contributors to rising sea levels in the region.
"The mass loss of these glaciers is increasing at an amazing rate," said Isabella Velicogna of UCI and NASA's Jet Propulsion Laboratory, who co-authored the report. She added that the changes "are proceeding very fast."
The study examined more than two decades' worth of data on "mass balance" of glaciers in the Amundsen Sea Embayment--including "how much ice the glaciers gain and lose over time from accumulating or melting snow, discharges of ice as icebergs, and other causes"--between 1992 and 2013.
The glaciers in the region lost mass throughout that entire period, at an ever-increasing speed. In fact, they are shedding roughly 91.5 billion tons of ice every year at a rate which grew by an average of 6.7 billion tons annually since 1992.
That rate is "almost three times the rate of increase for the full 21-year period," the authors wrote. "By comparison, Mt. Everest weighs about 161 gigatons (177 billion U.S. tons), meaning the Antarctic glaciers lost an amount of water weight equivalent to Mt. Everest every two years over the last 21 years."
The study's lead author Tyler Sutterley, a doctoral candidate at UCI, noted that "Previous studies had suggested that this region is starting to change very dramatically since the 1990s, and we wanted to see how all the different techniques compared. The remarkable agreement among the techniques gave us confidence that we are getting this right."
In May, a separate joint NASA-UC Irvine report discovered that the eventual glacier loss "appears unstoppable," according to that team's lead researcher, Eric Rignot. Because the majority of West Antarctica's ice sheet is attached to a sub-sea level ice bed, warmer ocean currents are able to eat away at the "grounding line"--the area where the ice meets the bed.
According to that study:
When ice shelves lose mass, they lose the ability to hold back inland glaciers from their march to the sea, meaning those glaciers can accelerate and thin as a result of the acceleration. This thinning is only conducive to more grounding line retreat, more acceleration and more thinning. In this equation, more ice flows to sea every year and sea level rises.
The Amundsen Sea is also vulnerable to a much warmer regional ocean current than other parts of West Antarctica, the earlier study found.
According to Velicogna, glacier and ice sheet behavior around the globe is the greatest uncertainty in predicting future sea levels. In October, the Australian National University found that they are rising at an unprecedented rate, while the Lawrence Livermore National Laboratory discovered that same month that the rate of ocean warming has been vastly underestimated.
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