Study Finds Warm Ocean Currents Cause Majority of Ice Loss From Antarctica
Posted on April 26, 2012
A new study has found that warm ocean currents melting the underside of ice shelves are the dominant cause of recent ice loss from Antarctica. The new study used measurements from NASA's Ice, Cloud, and land Elevation Satellite (ICESat). The scientists used a combination of satellite measurements and models to differentiate between the two known causes of melting ice shelves: warm ocean currents thawing the underbelly of the floating extensions of ice sheets and warm air melting them from above.
The researchers concluded that 20 of the 54 ice shelves studied are being melted by warm ocean currents. The ocean-driven thinning is responsible for the most widespread and rapid ice losses in West Antarctica, and for the majority of Antarctic ice sheet loss during the study period. The finding, published in the journal Nature, also brings scientists a step closer to providing reliable projections of future sea level rise.
Here is an animation that shows the circulation of ocean currents around the western Antarctic ice shelves. The shelves, which are being melted by warm ocean currents, are indicated by the rainbow color. Red is thicker, while blue is thinner.
Hamish Pritchard of the British Antarctic Survey in Cambridge, United Kingdom, and the lead author of the study, says, "We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt. The oceans can do all the work from below."
To map the changing thickness of almost all the floating ice shelves around Antarctica, the team used a time series of 4.5 million surface height measurements taken by a laser instrument mounted on ICESat from October 2003 to October 2008. They measured how the ice shelf height changed over time and ran computer models to discard changes in ice thickness because of natural snow accumulation and compaction. The researchers also used a tide model that eliminated height changes caused by tides raising and lowering the ice shelves.
ICESat was the first satellite specifically designed to use laser altimetry to study the Earth's polar regions. It operated from 2003 to 2009. Its successor, ICESat-2, is scheduled for launch in 2016.
Jay Zwally, ICESat project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., says, "This study demonstrates the urgent need for ICESat-2 to get into space. We have limited information on the changes in polar regions caused by climate change. Nothing can look at these changes like satellite measurements do."