CLIMATEWIRE | Ominous clouds rippled overhead, and scientist Jason Box raced to reach shelter before the rain hit.
Box, a glaciologist with the Geological Survey of Denmark and Greenland, had been camping with colleagues on the Greenland ice sheet last Friday when the weather began to turn.
As the team rushed to get off the ice, Box was struck by how warm the air felt on his face. It reminded him of hot Chinook winds that sweep through Colorado in the wintertime, melting snow and ice in their path.
He was right to find it foreboding. Over the next few days, the warm weather triggered a major melting episode in Greenland — a stunning event for September, which typically marks the end of the ice sheet’s melt season.
During the episode’s peak Saturday, around 12 billion tons of ice melted and ran off into the sea. Scientists estimate that more than 200,000 square miles of the ice sheet — an area bigger than California — were affected by the melting.
Greenland is already the most significant contributor to sea level rise. This month's record melt event has only added to the planet's woes as human-caused greenhouse emissions continue to rise, heating the earth and changing the rainfall patterns we have built our civilization on.
Recent research has found that Greenland melting of zombie ice (ice still attached to the edges of the ice sheet but does not gain mass) will lead to almost a foot of sea-level rise no matter what we do to stop pumping C02 into the atmosphere.
For the second year in a row, a late fall melting event has smashed records. It was one of the tenth largest melt events in Greenland on record.
Scientists suggest that the melting covered 200,000 square miles on the island. The summit also melted during the astonishing event. NASA noted that historically, a summit melt event occurred once every 300 years; now, that's down to 4 years.
September first is the end of the island's melt season. This melt event highlights not only the intensity of melting events but also the increasing length of the melting season, as noted by Maurice van Tiggelen, a polar scientist from the Netherlands, in an email to the Capital Gang.
As you recall, last year's extreme late-season melt event (brought to you by an Atmospheric River) and the current event (the warmth from the south) included copious amounts of rainfall and moist air, which now are increasingly common in Greenland. Jason Box compared the moisture to the condensation you see on your kitchen window. The melt event was over four days long.
The Capital Weather Gang of the Washington Post writes:
Between Friday and Monday, several weather stations recorded their maximum air temperature for the entire year. Parts of western Greenland rose as high as 36 degrees Fahrenheit (20 degrees Celsius) above normal for this time of the year. The summit, traditionally the coldest part of the ice sheet, even rose above the melting point Saturday according to NOAA observations at the National Science Foundation's Summit Station.
“It’s truly amazing to see a heat wave like this cover Greenland in September,” Ted Scambos, a senior research scientist at the University of Colorado, said in an email. “For the first time on record, temperatures at summit exceeded the melting point in September, on the afternoon of Sept. 3.”
The heat spurred melting across about 35 percent of the ice sheet last weekend — widespread melting of the sort usually observed in July. Typically, only 10 percent of the ice sheet surface is melting in early September.
Fettweis explained that meltwater runoff is important to track because it can reach the ocean and contribute to sea-level rise. A portion of the runoff can also be retained into the snowpack and refreeze during the winter. However, he said, this unusually late melting could favor the formation of ice slabs at the top of the snowpack. The ice slabs could prevent meltwater from percolating through the snowpack, meaning it could instead enter the ocean, further contributing to sea-level rise.
“If such events will occur in the next summers (which is very likely), the sea-level contribution will [grow] larger,” Fettweis wrote in an email.
“Greenland’s ice margin can’t tolerate the conditions that are becoming increasingly common for it. This event is typical of those destabilizing conditions,” Scambos said.
Outside of the latest event, this year’s melt season in Greenland was fairly moderate. Before this heat wave, the most notable action was a “heat ripple” that caused moderate melting in mid-July, and the number of melt days was near average after the event.