HEAT WAVE IN GREENLAND TRIGGERS RECORD EARLY START TO ICE MELT SEASON...

Humbolt Glacier in northern Greenland. Image: NASA

It may be a cold start to spring in the Midwest and eastern U.S., but in Greenland, more than 2,000 miles to the north, it's been positively balmy lately...

On Monday, when Boston had a high temperature of 60 degrees Fahrenheit, Kangerlussaq, Greenland, which serves as an important logistical hub for scientific research throughout the island, saw a record high temperature of 17.8 degrees Celsius, or 64.4 degrees Fahrenheit. 

This was the warmest April temperature on record at that location, and it nearly set an all-time warm temperature record for Greenland as a whole, which is the world's largest island.

Melt area in Greenland on April 10 and 11, 2016. Image: Polar portal

The unusually mild weather, which was accompanied by rain, set the annual ice melt season into gear about a full month earlier than it has been recorded before. 

According to the Polar Portal, which is a website funded by the Danish Energy Agency that tracks sea and land ice developments, the previous record earliest start to the Greenland melt season was on May 5. 

On April 11, satellite data showed that almost 12 percent of the Greenland ice sheet had more than 1 millimeter of ice melt as of April 11, following the kick off to the melt season on April 10. (The melt season formally begins when an area of 10 percent or greater of the ice sheet is melting.)

“We had to check that our models were still working properly,” Peter Langen, a climate scientist at the Danish Meteorological Institute (DMI) told the Polar Portal. 

Making this premature melt season more remarkable is the fact that of the top 3 earliest starts to the melt season since such data began in 1979, all of them occurred in May, the DMI's data shows. 

On Monday, temperatures were above freezing even at 6,000 feet in elevation, a height that rarely sees such mild temperatures even in the middle of the summer.

The Summit Station, at an elevation of nearly 11,000 feet, also set a high temperature record on Monday of minus-6.6 degrees Celsius, or 20 degrees Fahrenheit.

The unusual warmth was driven by a strong, persistent ridge of high pressure near Greenland combined with the airflow around low pressure systems to the west the island. These weather systems funneled relatively mild air northeastward across Greenland from lower latitudes. 

Computer model forecasts show the mild conditions persisting on Wednesday and Thursday, before transitioning to a somewhat colder regime later in the week.

The melt season is likely to proceed in fits and starts from here on out, with refreezing taking place in most areas of the island this month. 

Temperature anomalies in degrees C in the lower atmosphere, showing unusual warmth over Greenland. Image: Weatherbell Analytics

This refreezing process, though, releases heat into the snow, which can make the ice pack more prone to melting later in the spring.

Greenland contains the second-largest ice sheet in the world. If it were to all melt, global sea level would rise by about 20 feet, swallowing coastal cities from New York to Shanghai. 

Increased melting in recent years has disrupted ocean circulation in the North Atlantic, leading to what many scientists are referring to as a "cold blob" of water southeast of Greenland. 

The Greenland ice sheet has shed an estimated 1 trillion tons of ice since 1900, with a doubling in the rate of ice loss from 2003 to 2010, according to a study published last year in the journal Nature.

Much of that ice has been lost at the margins of the ice sheet, at places where ices terminate in floating ice tongues. Warming ocean waters are eating away at the underbelly of these outlet glaciers.

Ice melt in other parts of Greenland leads to a complex maze of waterways flowing under the ice sheet, lubricating it and allowing glaciers to speed their movement into the sea.

The early start to the Greenland melt season comes in the same year as the North Pole saw a brush with above-freezing temperatures when a powerful storm dragged warm air to the top of the world in early January.

As is the case with Arctic sea ice, how Greenland's 2016 melt season turns out will depend significantly on transient weather conditions during the late spring and summer. In 2012, at least 95 percent of the ice sheet experienced some melting due to a prevailing weather pattern that favored unusually mild conditions there. However, that record has not been tied or broken since.


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