These changes, over the relatively short period of less than a century, appear to be unprecedented. Greenland’s ice sheet shrank between 10,000 and 7,000 years ago, and has been slowly cumulating over the past 4,000 years. The current melting will reverse that pattern and within the next 1,000 years, if global heating continues, the vast ice sheet is likely to vanish altogether. If greenhouse gas emissions continue to rise strongly, the rate of melting could accelerate further to be four times greater than anything found in the past 12,000 years.
The team behind the latest Greenland study made their estimates by producing a computer model of a section of the south-western region of the ice sheet over the past 12,000 years and then projecting forward to the end of this century. They checked their findings against what we can tell actually occurred with the ice, through satellite measurements and other instruments, and also by mapping the position of boulders containing beryllium-10. These are deposited by glaciers as they move, and measurements of beryllium-10 can reveal how long the boulders have been in position, and therefore where the edge of the ice sheet was when the boulder was deposited.
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