A major warm spell has caused nearly half the surface of the Greenland ice sheet to start melting, something that’s highly unusual for this time of year. And while this spike may pass, the gears could already be in motion for record-setting melt on the ice sheet’s western flank.
Greenland has been scorching (by Greenland standards) for the past few days, with temperatures rising 10-20 degrees Celsius (18-36 degrees Fahrenheit) above normal across the island. Ruth Mottram, a climate scientist with the Danish Meteorological Institute, told Earther that the weather station at the top of the ice sheet saw temperatures reach above freezing on Wednesday and they were headed that way again on Thursday. That puts them just a degree or so away from setting the all-time heat record for June, which is currently held by June 2012.
The spike in temperatures has caused a spike in melt. Roughly 45 percent of the ice sheet surface has been melting. Normally, less than 10 percent of the ice sheet surface is melting at this time of year. According to data from the National Snow and Ice Data Center, Wednesday set a daily record for the widest melt area on that date, with 275,000 square miles—an area bigger than Texas—of the ice sheet’s surface becoming a slushy, watery mess. Mottram said the much of the ice is likely to refreeze once the heat breaks, but it will be more primed to melt later in the season.
Indeed, there are a number of factors working against Greenland’s ice right now. A spurt of heat in April kickstarted the second-earliest start to the melt season on record. Mottram noted that the weather station on the summit of Greenland read minus-1.2°C [29.8 degrees Fahrenheit] on April 30, its warmest ever April recording. May continued a trend of warmer than normal weather.
“In fact, one of my weather forecaster colleagues rather drolly remarked that you would have been more successful growing tomatoes outside in Kangerlussuaq [in western Greenland] than in most of Denmark this May, due to the very warm May without frosts there,” she wrote in an email.
This going-on-three months of warm temperatures comes after a very dry winter for Greenland, particularly on the ice sheet’s western edge. Ice sheets need snow to gain mass but also to act like a bright, white shield that reflects sunlight away, something scientists call the albedo effect. The low snowpack means the ice sheet’s protection is much weaker than normal. Greenland’s ice also has all sorts of schmutz on it as wildfire soot and other forms of black carbon that darken its surface and absorb more of the sun’s energy. Xavier Fettweis, a Greenland researcher at the University of Liege, called this situation “exceptional.”
“Due to a lower winter accumulation than normal, the bare ice area has been exposed very early in this area enhancing the melt due to the melt-albedo feedback,” he told Earther. “Therefore, at the beginning of the melt season, the snowpack along the west coast is now preconditioned to break records of melt.”
And unfortunately, record melt is likely to be in Greenland’s future due to the weather. The Arctic is warming twice as fast as the rest of the world, but certain natural climate patterns can enhance that warmth over Greenland. In particular, the North Atlantic Oscillation (NAO), a seesaw of high and low pressure areas, can really crank up the heat on Greenland when it’s in a negative phase. In that setup, higher than normal pressure plops itself over Greenland and parts of the Arctic and can lock in warm weather and sunny skies. The NAO is negative right now and forecasts indicate it’s like to stay negative all summer.
Which means this is almost certainly not the last heat wave Greenland will see. It remains to be seen if we’ll get a meltdown like July 2012 when the entire ice sheet’s surface destabilized, but regardless, it’s a disconcerting June for an ice sheet that, if it completely melted away, would raise sea levels by about 24 feet.