Shepherd, of Leeds University in the UK, who led the study.
He said the thinning of some ice streams had extended 300 miles inland along their 600-mile length. “More than 50% of the Pine Island and Thwaites glacier basins have been affected by thinning in the past 25 years. We are past halfway and that is a worry.”
Researchers already knew that ice was being lost from West Antarctica, but the new work pinpoints where it is happening and how rapidly. This will enable more accurate projections to be made of sea level rises and may aid preparations for these rises.
In the recent past, snow falling on to Antarctica’s glaciers balanced the ice lost as icebergs calved off into the ocean. But now the glaciers are flowing faster than snow can replenish them.
“Along a 3,000km [1,850-mile] stretch of West Antarctica, the water in front of the glaciers is too hot,” he said. This causes melting of the underside of the glaciers where they grind against the seabed. The melting lessens the friction and allows the glaciers then to slide more quickly into the ocean and therefore become thinner.
“In parts of Antarctica, the ice sheet has thinned by extraordinary amounts,” Shepherd Said.www.theguardian.com/...
“The Antarctic ice sheet is one of the two polar ice caps of the Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth. It covers an area of almost 14 million square kilometres (5.4 million square miles) and contains 26.5 million cubic kilometres (6,400,000 cubic miles) of ice.[2] A cubic kilometer of ice weighs approximately one metric gigaton, meaning that the ice sheet weighs 26,500,000 gigatons. Approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to about 58 m of sea-level rise.[3] In East Antarctica, the ice sheet rests on a major land mass, while in West Antarctica the bed can extend to more than 2,500 m below sea level.
In contrast to the melting of the Arctic sea ice, sea ice around Antarctica was expanding as of 2013.[4] Satellite measurements by NASA indicate a still increasing sheet thickness above the continent, outweighing the losses at the edge.[5] The reasons for this are not fully understood, but suggestions include the climatic effects on ocean and atmospheric circulation of the ozone hole,[4] and/or cooler ocean surface temperatures as the warming deep waters melt the ice shelves.”en.wikipedia.org/...
Visualization of NASA's mission Operation IceBridgedataset BEDMAP2, obtained with laser and ice-penetrating radar, collecting surface height, bedrock topography and ice thickness.
en.wikipedia.org/...