|December 11, 2018|
East Antarctica is losing ice faster than anyone thought
|East Antarctica was supposed to be the stable side of the icy continent, whose western flank is losing ice fast1. But glaciologists are finding that the closer they look at East Antarctica, the more change they see.|
Four small glaciers in a region known as Vincennes Bay are thinning at surprisingly fast rates, researchers reported on 10 December at a meeting of the American Geophysical Union in Washington DC.
"People think that East Antarctica is stable," says Helen Fricker, a glaciologist at the Scripps Institution of Oceanography in La Jolla, California. "But it's where we should be looking."
The glaciers are responding to warm ocean waters that now reach much closer to East Antarctica's icy edge than in years past --- and might continue to do so. "It's a signal of what's to come," says Catherine Walker, a glaciologist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who led the team analysing the glaciers.
The Vincennes Bay glaciers lie next to East Antarctica's awakening giant, a massive river of ice known as Totten. Totten's flow to the sea sped up between 2001 and 2007, most likely because warm water was intruding beneath the floating end of the glacier and melting it from below2.
Now, the giant's neighbours might also be rousing themselves, Walker says. Vincennes Bay caught her eye as she was looking at a map of how quickly ice flows in different parts of Antarctica. The four glaciers --- Vanderford, Adams, Bond and Underwood --- seemed to be accelerating their course to the sea.
That's important, because both Totten and the Vincennes Bay glaciers drain an enormous buried basin that holds enough ice to raise global sea levels by 9 metres.
Walker and her colleagues decided to take a closer look at Vincennes Bay to calculate how much ice was being lost. And for that, they needed a 3D view of how the glaciers' surfaces were moving up or down as they thickened or thinned. The team studied satellite measurements, including data on ice height gathered by NASA's ICESat between 2003 and 2009, and by the European Space Agency's Cryosat-2 since 2011. By combining these streams of information, the scientists generated monthly glimpses of how ice heights were changing throughout the year.
The work draws on a NASA-funded project, called Inter-mission Time Series of Land Ice Velocity and Elevation (ITS LIVE), which stitches together decades of ice-speed and height measurements made by different satellites. The result is a comprehensive look at how ice flows in three dimensions over time. "It gives us a new set of glasses to look at the change with," says Walker.
With this sharper vision, the scientists could see how the height of the Vincennes Bay glaciers shrank in the 1990s as they shed ice. The glaciers bulked up in the late 2000s, before they started to thin again in 2010. Now, the height of their surface ice is falling an average of 0.5 metres a year, much faster than their neighbour Totten is changing.
To determine how the ocean might be influencing ice loss, Walker looked at data from oceanographic floats, plus the occasional deep-diving seal that researchers kitted out with temperature probes, which showed ocean temperatures in the area beginning in 2008. Temperatures started to warm around 2010, when the Vincennes Bay glaciers began to thin.
How warm the water gets off East Antarctica varies from year to year, based on factors such as wind speed and direction, and the presence or lack of sea ice. But in general, climate scientists expect warm waters to make their way closer to East Antarctica more regularly in the future as weather patterns change. "As long as things keep going the way they're going, we should expect more warm water," Walker says.
And that could mean more quick changes on the way for East Antarctica.