https://www.science.org/doi/10.1126/science.ade4248 Measurements made on subglacial sediment from the Camp Century ice core in northwestern Greenland show that the location was ice free during the interglacial that occurred around 400,000 years ago.
The absence of ice at that location means that the Greenland Ice Sheet must have contributed more than 1.4 meters of sea-level equivalent to the high sea-level stand, when the average global air temperature was similar to what we will soon experience because of human-caused climate warming.
If Greenland’s ice sheet saw rapid melting during a period of moderate warming, it may be more sensitive to human-caused climate change than previously understood – and will be vulnerable to irreversible, rapid melting in coming centuries. “It’s really the first bulletproof evidence that much of the Greenland ice sheet vanished when it got warm,” Bierman said. “Greenland’s past, preserved in 12 feet of frozen soil, suggests a warm, wet, and largely ice-free future for planet Earth,” he added.
The potential implications for sea level rise are enormous, Tammy Rittenour, a professor from Utah State University and study co-author said in a statement. “We are looking at meters of sea level rise, probably tens of meters. And then look at the elevation of New York City, Boston, Miami, Amsterdam. Look at India and Africa – most global population centers are near sea level.”