Scientists have found the first evidence that links melting ice in Greenland to Arctic amplification – faster warming of the Arctic compared to the rest of the Northern Hemisphere as sea ice disappears.
The findings show that the predicted effects of Arctic amplification, as described in previous studies, occurred over northern Greenland during summer last year, including a northern swing of the jet stream that reached latitudes never before recorded in Greenland at that time of year.
The Greenland ice sheet, Earth’s second largest after Antarctica, holds enough ice that if it were to melt entirely, it would raise average global sea level by about 7 metres.
Learning more about the drivers of melting is essential to discerning 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.
“During the past two decades, we have seen increasing melt from the Greenland ice sheet, culminating in a very large melt event in the summer of 2012,” said Thomas Mote, professor at University of Georgia in the US.
“Last year was unique in the extensive melting that occurred on the northern reaches of the ice sheet, an area that usually has rather modest melt compared to southern Greenland.
“We identified an unusual configuration of the jet stream toward northern Greenland that led to this melt pattern,” said Mote.
Rising global temperatures are melting Arctic sea ice, leaving dark open water that 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.
The study was published in the journal Nature Communications.