As Greenland loses ice, global sea levels will rise—and its own will fall
By Evan Howell, Science.
Excerpt: Seas will rise this century—but not uniformly.... In the very places where glaciers are melting and shrinking, the land beneath will rebound as the burden eases, meaning seas may fall even as the meltwater causes them to rise elsewhere. A new study shows that in Greenland—whose rapidly melting ice sheet accounts for about one-fifth of current sea level rise—this paradox will mean expanding coastlines, dried-up fjords, and future complications. Published today in Nature Communications, the research shows portions of Greenland’s coast will rebound far more sharply than expected, causing seas to fall by anywhere from 1 to nearly 4 meters by 2100. Western and southern Greenland...will likely bear the brunt of the retreat, posing major problems for shipping and food security. ...Changes in the mass of Greenland’s enormous ice sheet, which is roughly three times the size of Texas and in some places more than 3 kilometers thick, are the culprit. ...As it melts, the underlying land springs back and rises, effectively lowering relative sea levels. ...For decades, researchers thought only the planet’s springy crust could respond on human timescales, rebounding by small amounts. Below the crust, the mantle’s slow, honeylike heave was thought to take millennia to relax. But ...Scientists now show that when the ice shrinks, the mantle flows faster than expected, to the point that this supposedly “long-term” process kicks in within decades. ...This study also builds on evidence from the past. For instance, geologic traces from a cold snap known as the Little Ice Age—roughly spanning the 14th through the 19th centuries, which may have hastened the Vikings’ departure from Greenland—show glacier volumes and sea level shifted quickly....