The Greenland ice sheet melting isn’t abnormal. But the suddenness of this week’s melt caught scientists off guard. 12% of the ice sheet was covered in a layer of melt water at least 1 millimeter thick.
Researchers at the Danish Meteorological Institute (DMI) first thought their models were bugging out. “We had to check that our models were still working properly,” said Peter Langen, a climate scientist at DMI. Their models were right. Climate stations on the ice sheet were reporting temperatures above 10 degrees Celsius in spots. That’s 50 degrees Fahrenheit. Those aren’t temperatures you generally think of in Greenland, but they do happen in the summer.
What’s surprising scientists this year is how early it’s happening. The earliest scientists have ever seen the melt area larger than 10% was in May – May 5th, 2010, May 8th, 1990 and May 8th, 2006.
You can see how quickly the melt area expanded over two days earlier this week in the image below. The right side of the image shows a graph indicating the percentage of ice melt and when it typically happens.
The sudden rise in temperatures extended into higher elevations. One site at just over 6,000 feet above sea level saw a maximum temperature of 3.1 degrees Celsius. “This would be a warm day in July, never mind April,” said Robert Fausto, a scientist who helped compile the melt data.
What’s driving this increase in temperatures? Check out the map below showing the flow pattern for Greenland on Monday.
Anyone who turns on the Weather Channel in the morning knows that’s a ridge. And a ridge means higher temperatures. Martin Stendel of the DMI explains what we are looking at. “It is a very unusual situation, especially so early in the year, with very cold air and deep low pressure systems to the west and east of Greenland and very warm air forming a ‘cap’ over the island. This helped to force a frontal system with very warm air up the west coast bringing rain over the ice sheet,” said Stendel.
Some of you living in the northeast saw this weather pattern first hand with a not-so-normal April snow. I just want the 80s to get to Alabama and stay here.
Stendel added, “The very cold weather by contrast in north eastern Greenland is exactly what we would expect with this pattern.”
So what does the early rainfall and meltwater on the ice sheet mean? In April, the meltwater tends to refreeze as temperatures don’t typically stay this warm for long. But this leads into another issue. I’ll let Professor Jason Box of the Geological Survey of Denmark and Greenland explain. “Melt water 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.”
Bottom line? The early ice melt could have bigger impacts that are felt as Greenland enters the summer months.