Within the ice sheet, the Thwaites and Pine Island glaciers are particularly vulnerable to global warming and are already contributing to rises in sea level.
Now, a new study led by the University of Maine and the British Antarctic Survey, including academics from Imperial College London, has measured the rate of local sea-level change - an indirect way to measure ice loss - around these particularly vulnerable glaciers.
They found that the glaciers have begun retreating at a rate not seen in the last 5,500 years. With areas of 192,000 km2 (nearly the size of the island of Great Britain) and 162,300 km2 respectively, the Thwaites and Pine Island glaciers have the potential to cause large rises in global sea level.
Co-author Dr Dylan Rood of Imperial's Department of Earth Science and Engineering said: "We reveal that although these vulnerable glaciers were relatively stable during the past few millennia, their current rate of retreat is accelerating and already raising global sea level.
"These currently elevated rates of ice melting may signal that those vital arteries from the heart of the West Antarctic Ice Sheet have been ruptured, leading to accelerating flow into the ocean that is potentially disastrous for future global sea level in a warming world. Is it too late to stop the bleeding?"