Blistering temperatures and rainfall over Greenland have jump-started the summer melt season weeks early. On Monday, a stunning 12 percent of Greenland’s massive ice sheet was melting — “smashing by a month the previous records of more than 10 percent of the ice sheet melting,” according to the Danish Meteorological Institute (DMI).
DMI scientists were “at first incredulous.” One DMI climate scientist said, “We had to check that our models were still working properly.” But in fact, temperatures over parts of Greenland this month have been measured as high as 17.8°C — a scorching 64°F.
“Even weather stations quite high up on the ice sheet observed very high temperatures on Monday,” explained Robert Fausto of the Geological Survey of Denmark and Greenland (GEUS). At one “site at 1840 meters [1.1 miles] above sea level, we observed a maximum temperature of 3.1°C [37.6°F]. This would be a warm day in July, never mind April.”
Here are the key charts from DMI:
Greenland holds the second-biggest chunk of land-locked ice in the world (after Antarctica), and its melt, by itself, could raise sea levels 20 feet. Equally worrisome, accelerated Greenland ice melt has been implicated in the slowdown of the Gulf Stream system.
That slowdown, in turn, appears to be one reason “ocean temperatures off the U.S. east coast are warming faster than global average temperatures,” as Stefan Rahmstorf, Co-Chair of Earth System Analysis at the Potsdam Institute for Climate Impact Research, has explained. And that faster warming of the coastal U.S. has, in turn, helped supercharge monster storms like Blizzard Jonas and Superstorm Sandy.
Significantly, a new study this month “has found that the climate models commonly used to simulate melting of the Greenland ice sheet tend to underestimate the impact of exceptionally warm weather episodes on the ice sheet.”
Fausto, the lead author, has said, “When we were analysing our weather station data, we were quite surprised that the exceptional melt rates we observed were primarily caused by warm and moist air because ice sheet wide melt is usually dominated by radiant energy from sunlight.”
So unusually warm blasts of moist air are a key driver of the accelerating disintegration of the Greenland ice sheet.
How anomalously warm was the blast of moist air that brought Greenland high temperatures and rain this week? It was upwards of 36°F above normal over large parts of the ice sheet:
And, while this kind of extraordinary warmth won’t last, sometime this week we might see temperatures up to 57°F above normal.
In the spring, meltwater and rainfall on the ice sheet generally goes into the snow and refreezes. That said, “Meltwater refreezing releases heat into the snow at depth, reducing the amount of heating needed for melt to start and forming ice layers that can help melt water run off the ice sheet earlier with climate warming,” according to Jason Box of GEUS, who leads a major effort to understand how ice melt and rainfall can lead to unexpectedly fast (non-linear) runoff.
With both Greenland and Antarctica now clearly disintegrating faster than the climate models had projected, we must redouble our efforts to keep total warming below 2°C.