Monitoring Antarctica from space has revealed how its ice is being lost to the oceans, providing crucial insight into the continent's response to a warming climate, scientists say.
The researchers, including those from the University of Leeds in the UK, reviewed decades of satellite measurements to reveal how and why Antarctica's glaciers, ice shelves, and sea ice are changing.
The study, published in the journal Nature, found that ice shelf thinning and collapse have triggered an increase in the continent's sea level contribution.
It also found that although the total area of sea ice surrounding Antarctica has shown little overall change during the satellite era, there are signs of a longer-term decline when mid-twentieth century ship-based observations are considered.
"Antarctica is way too big to survey from the ground, and we can only truly understand the trends in its ice cover by looking at the continent from space," said Andrew Shepherd, a professor at Leeds.
In West Antarctica, ice shelves are being eaten away by warm ocean water, and those in the Amundsen and Bellingshausen seas are up to 18 per cent thinner than in the early 1990s, researchers said.
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At the Antarctic Peninsula, where air temperatures have risen sharply, ice shelves have collapsed as their surfaces have melted.
Altogether, 34,000 square kilometres (km2) of ice shelf area has been lost since the 1950s, they said.
"Although breakup of the ice shelves does not contribute directly to sea-level rise - since ice shelves, like sea ice, are already floating - we now know that these breakups have implications for the inland ice: without the ice shelf to act as a natural buffer, glaciers can flow faster downstream and out to sea," said Helen Amanda Fricker, a glaciologist at University of California San Diego in the US.
More than 150 studies have tried to determine how much ice the continent is losing. The biggest changes have occurred in places where ice shelves - the continent's protective barrier - have either thinned or collapsed.