Ramp-Up in Antarctic Ice Loss Speeds Sea Level Rise

Rodiano Bonacci
Giugno 17, 2018

East Antarctica's ice sheet, however, is gaining mass at an average rate of 5 billion metric tons per year.

From 1992 to 2011, Antarctica lost almost 84 billion tons of ice a year (76 billion metric tons).

In the big picture, the new findings suggest this: instead of the Antarctic ice sheet contributing 0.2 mm of water to rising sea levels, it is now three times that at 0.6 mm annually.

As well as being a major cause of sea-level rise, scientists say the oceans around Antarctica are a key "carbon sink" - absorbing huge amounts of greenhouse gases helping to mitigate the impacts of climate change. Antarctica is, on balance, losing its ice sheets and raising the world's sea levels.

More than 3.3 trillion tons of ice have already melted away since 1992, contributing to a quarter-inch rise (7.6 millimeters) in global sea levels - 40 percent of which (or a 3-millimeter rise) taking place during the last five years, notes Eurek Alert.

Whether Antarctic mass loss keeps worsening depends on choices made today, argues DeConto, who co-authored a separate paper in this week's Nature outlining two different visions for Antarctica's future in the year 2070.

Isabella Velicogna, another co-author of the study said,"I think we should be anxious". Theoretically, if they melted entirely, sea level worldwide would rise by 58 meters (190 feet), posing an existential threat to small island nations and coastal communities. "To do this, we need to keep watching the ice sheet closely, but we also need to look back in time and try to understand how the ice sheet responded to past climate change". Altogether, 13,000 square miles of ice shelf area has been lost since the 1950s.

Ice losses from Antarctica have tripled since 2012, increasing global sea levels by 0.12 inch (3 millimeters) in that timeframe alone, according to a major new worldwide climate assessment funded by NASA and the European Space Agency (ESA).

Antarctica is not the only contributor to sea-level rise.

Scientists from the University of Maryland, the University of Leeds, and the University of California have reviewed decades of satellite measurements to reveal how and why Antarctica's glaciers, ice shelves, and sea ice are changing. "But where there is loss of sea ice, storm-generated ocean swells can easily reach the exposed ice shelf, causing the first few kilometers of its outer margin to flex".

Part of West Antarctica, where most of the melting occurred, "is in a state of collapse", said co-author Ian Joughin of the University of Washington. This NASA illustration shows where the ice is moving fastest; areas in red have the fastest flow, followed by those in pink and purple.

New and improved satellite missions, such as Sentinel-3, the recently launched Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) and the eagerly awaited ICESat-2, will continue to give researchers more detailed insights into the disappearance of Antarctic ice.

"If we don't get on top of climate change and make good policy decisions now, we will end up with a world we haven't seen for three million years, with a sea level up to 30 metres higher than now".

This week's issue of Nature features several other reports on Antarctica and its future.

That exact location matters, as the communities living on the US coastline will see the sea levels rise, according to climate scientists. By mapping our measured sea level contribution on top of these projections, we found that our previous assessment of Antarctic sea level contribution, which measured ice loss until 2012, was tracking the IPCC's lowest projection.

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