Greenland Ice Melt Caused by Arctic Amplification

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Researchers led by Asa Rennermalm of Rutgers University and including the University of Georgia's Thomas Mote measure meltwater runoff from the ice sheet margin in Greenland during summer 2013.

The melting of ice in Greenland has been linked to faster warming of the Arctic as compared to rest of the places in the Norther Hemisphere – something which is known as Arctic amplification.

The link has been established through a new study by an international team of researchers from University of Georgia, Columbia University, University of Liege, City College of New York, University of Leeds and the University of Sheffield and published in Nature Communications.

The study is the first to provide evidence for this link predicted by previous studies by showing that effects of Arctic amplification occurred over northern Greenland during summer 2015, including a northern swing of the jet stream that reached latitudes never before recorded in Greenland at that time of year.

One of the primary reasons why the Greenland ice sheet is the focus of multiple studies is that it is the second largest ice sheet in the world after Antarctica and if it were to melt in its entirety, according to estimates, it will release enough water to raise the global sea levels by a whopping 7 meters, or almost 23 feet. Studies of this area is key to understanding how much sea level will rise and by how much in the future and how Greenland’s freshwater runoff will affect ocean circulation and ecology.

Researchers have been tracking the Greenland ice sheet melts for years and according to reports, the last two decades have witnessed increasing melt from the Greenland ice sheet and the one in year 2012 was one of the largest ever recorded.

Another thing that researchers point out in their study is that the year 2015 has been a unique one as well considering that there was extensive melting recorded on the northern reaches of the ice sheet, which is unusual considering that this area has been linked with rather modest melt compared to southern Greenland.

From the global increase in temperature point of view, the more the temperatures increase, the more open water there is because of increased melting. This water absorbs more solar radiation and causes faster warming in the Arctic. While Arctic amplification is well documented, its effects on the atmosphere are still debated. One theory among scientists is that the shrinking temperature difference between the Arctic and the temperate zone will lead to a slowing of the jet stream. Normally, when the jet stream circles the northern latitudes, the frigid polar air is separated from warmer air in the south. Slower winds, however, could create wilder swings that would allow warm, humid air to penetrate farther north.

Northwest Greenland’s summer melt started last June when a high-pressure ridge squeezed off from the jet stream and moved westward over Greenland and hovered over the Arctic Ocean, the study shows.

Clear skies and warmer weather in northern Greenland from this high-pressure system resulted in record setting surface temperature and meltwater runoff in the northwest. With less summer snow falling and melting underway, northern Greenland’s reflectivity also decreased and the water absorbed more heat from the sun, further increasing melting.

Northern Greenland’s wind patterns also changed from the usual west to east direction to east to west. Only two other years on record show east to west wind averages in July and both were slower. Further, the jet stream’s northernmost ridge swung nearly 2 degrees farther north than the previous July record, set in 2009.

The same atmospheric pattern had a different impact on southern Greenland, where new melting records have been set over the past decade. The south saw more snow during summer 2015 and less melting than previous years.

The authors don’t fully confirm Arctic amplification as the cause of the warming, but say the results of their study fit the description of possible effects as predicted by other researchers. Whether the patterns seen in 2015 will continue in the future is uncertain. This spring, Arctic sea ice set another record low for its maximum extent for the year.

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