Winds Carve Away Antarctic Snow

A new study has found that powerful winds are removing massive amounts of snow from parts of Antarctica, potentially boosting estimates of how much the continent might contribute to sea level. Up to now, scientists had thought that most snow scoured from parts of the continent was simply redeposited elsewhere on the surface. However, the new study shows that in certain parts, called scour zones, some 90 percent—an estimated 80 billion tons per year—is instead being vaporized, and removed altogether. The finding means that scientists must adjust their models of how much mass Antarctica is losing, and how much it might lose in the future. The study appears this week in the journal Geophysical Research Letters.

Wind-scour zones, which cover about 7 percent of Antarctica, occur where winds persistently scrape away at the surface, sometimes for centuries.  The new study documented one area where winds have obliterated as much as 18 meters (more than 50 feet) of snow—equal to 200 years’ accumulation.  The scientists identified thousands of similar sites using satellite imagery. This persistent loss has created pockets where the surface is eroding about as fast as ice flows in. That means the surface retains its shape, but in fact is exporting mass. In the past, warmer climates have brought more snowfall to Antarctica, and this could happen again now, so knowing where all that snow ends up could become increasingly important.
The research was led by Indrani Das, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory.“We need to get the physics right.” said Das. “The ice surface and the scouring process are tied together with climate.”
As snow falls in Antarctica, it builds up layers on the ice sheet. Researchers can see these layers in radio-echo images and ice-core samples. In East Antarctica, where the researchers did their work, Das noticed irregularities on the radar images: landscapes where snow had accumulated as expected, and then sections where the layers disappeared for a few kilometers, then resumed. These were wind-scour zones, sometimes called “glaze” for their buffed ice surfaces. Das developed an empirical model, described in a 2013 Nature Geoscience paper, that could locate the scour zones. She then used satellite data from earlier research led by glaciologist Ted Scambos of the University of Colorado’s National Snow and Ice Data Center to validate it.