Satellites document alarming ice loss in Antarctica

Media playback is unsupported on your device                  Media caption Andrew Shepherd

Media playback is unsupported on your device Media caption Andrew Shepherd"The study incorporates 24 independent satellite assessments

We have found that since 1992 Antarctica has lost 2,720 billion tonnes of ice, raising global sea levels by 7.6mm. Unlike single-measurement studies, this team looked at ice loss in 24 different ways using 10 to 15 satellites, as well as ground and air measurements and computer simulations, Shepherd said.

"Satellites have given us an incredible, continent-wide picture of how Antarctica is changing", said Dr. Pippa Whitehouse, a member of the IMBIE team from Durham University, according to a University of Leeds press release.

The annual sea level rise that's attributed to Antarctica has tripled, from 0.2mm to 0.6mm, or from less than a tenth of an inch to almost a quarter of an inch, he says. Their mission is to produce the most comprehensive look at what's happening to the world's vulnerable ice sheets in Antarctica and Greenland.

- In the Southern Ocean around Antarctica, sea ice expands and contracts as ocean water freezes and melts throughout the year.

While the current ice loss measured is literally a drop in the ocean compared to Antartica's catastrophic potential to raise global sea level by as much as 58 metres (190 ft) if the ice sheets were to completely melt, the apparent acceleration in the latest satellite observations is enough to have scientists duly anxious.

"We should be anxious", said University of California Irvine's Isabella Velicogna, one of 88 co-authors. In East Antarctica the picture has been muddled as the ice sheet there gained mass in some years and lost mass in others. Suddenly removing the ice shelves attached to these sensitive areas could initiate glacier retreat and accelerate sea level rise. The upper end of this range would imply that most of the ice on the planet melted, enough to raise sea levels by 63 meters.

Reduced sea ice coverage since the late 1980s has led to increased exposure of ice shelves on the Antarctic Peninsula to ocean swells, causing them to flex and break.

Millimeters of sea level rise may not sound like much, but previous surveys suggested that Antarctica's massive ice sheets likely wouldn't be affected by climate change at all.

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"Continued ice loss in Antarctica is of great concern for humanity, affecting coastal communities, people, and infrastructure", she said in a statement. Together, the studies evaluate past and present conditions in Antarctica to determine the impact of climate change and human activity on the continent, and to present strategies for the future of its ecology and geology.

Much of the melt-off is coming from the Pine Island and Thwaites Glaciers, victims of climate change. These were a series of ancient cracks filled with marine ice, which resembled the features seen in areas with rapid melting.

"Some of the changes Antarctica will face are already irreversible, such as the loss of some ice shelves, but there is a lot we can prevent or reverse", said Martin Siegert, study co-author and professor at the Grantham Institute in London.

Lead author Andrew Shepherd of the University of Leeds told NPR that prior to 2012, Antarctica's ice losses had been contributing a "relatively small proportion" to global sea level rise.

"The data from GRACE's twin satellites show us not only that a problem exists, but that it is growing in severity with each passing year".

While we can't be sure that ice loss rates will continue to climb in this manner, researchers are concerned that the trend will remain upward.

But 40 per cent of that increase came from the last five years of the study period, from 2012 to 2017, when the ice-loss rate accelerated by 165 per cent.

"The detailed record shows an acceleration, starting around 2002, " said Beata Csatho, one of the study authors and a glaciologist at the State University of NY at Buffalo, in an e-mail. Forty percent of that loss has occurred in just the last 5 years, again underscoring the recent increase in losses. The water nibbles at the floating edges of ice sheets from below.

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