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As climate change brings warmer temperatures to Antarctica, scientists have generally believed that the continent could experience a subsequent increase in snowfall. But new research may obliterate that theory. Published in the Proceedings of the National Academy of Sciences, scientists discovered that gravity-based winds from interior Antarctica are causing snowflakes to disappear before hitting the ground, thus negating at least some of the expected increase in moisture. Changing climate there could increase the winds, leading to further snowfall loss. Antarctic snowfall totals are useful in understanding the mass balance of its ice sheets as well as their influence on sea levels, so the study has important implications in these research areas.

In 2015 and 2016, scientists utilized unprecedented radar and precipitation gauge systems to monitor precipitation patterns in the Adelie Land region of Antarctica.

"Precipitation in Antarctica is a big unknown because it's very remote, there are very few people, so not much is known about what's going on there," says study coauthor Alexis Berne of the Swiss Federal Institute of Technology. "And so we thought it would be a good idea to bring ... state-of-the-art remote sensing instruments to study precipitation in this environment."

The research team discovered that a considerable amount of snow was vanishing before reaching the ground, which they attributed to the cold katabatic winds cascading from higher elevations to the coast. The dry winds cause snowflakes floating in the air to sublimate, instantly changing them from a solid to a gaseous state and preventing them from ever reaching the ground and accumulating.

From their observations as well as atmospheric model simulations, the scientists determined that katabatic winds could reduce snowfall across Antarctica by 17%, and up to 35% around the lower elevations of East Antarctica.

Because it occurs so close to Earth's surface, the sublimation cannot be detected by satellite observations, which affects the accuracy of satellite-based snowfall estimations near the ground that are used to determine ice loss after calving and ice replacement after new snow falls. As Berne notes, if temperatures in Antarctica increase, "then the classical view is to say, well, warmer air, you can have more moisture in the air, so we should expect an increase in precipitation." But the new findings suggest much of that uptick in precipitation could be offset by the sublimation process, which would accelerate with any increase in the katabatic winds.

"Our point is we should be careful in evaluating the evolution of the ice mass balance, taking into account these processes," Berne says.

The study was released just as West Antarctica's Pine Island Glacier--one of the largest in the region and the fastest-melting glacier on the continent--calved a massive iceberg more than 100 square miles in size--more than 4 times the size of Manhattan. For more about that glacier, see the News & Notes section in the November 2017 BAMS. [SOURCE:]

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Publication:Bulletin of the American Meteorological Society
Date:Feb 1, 2018

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