Computer models and field measurement conducted by researchers from Rutgers University revealed that vanishing Arctic sea ice, extreme weather systems over Greenland and widespread surface ice melting on the massive island are all tied to global sea level rise.
Melting Arctic sea ice is largely driven by frequent "blocking-high" pressure systems during Greenland summers. Such weather systems spin clockwise, stay largely in place and can block cold, dry Canadian air from reaching the massive island. Consequently, the highs tend to enhance the flow of warm, moist air over Greenland, contributing to increased extreme heat events and surface ice melting.
The problem is that these weather events fuel sea level rise, according to study co-author Jennifer Francis, a research professor in Rutgers University's Department of Marine and Coastal Sciences. The Greenland ice sheet holds an enormous volume of frozen water that, if melted, would increase the global sea level by 20 to 23 feet. This, in turn, creates a "monstrous" issue for coastal communities around the world.
"I think this study does a good job of pinning down the fact that the [Arctic sea] ice is disappearing for a whole bunch of reasons - and that is causing the surface of Greenland's melt area to increase," Francis explained.
What's more is that the increased melting on the Greenland ice sheet in recent years may also be linked to cooler-than-normal ocean temperatures south of the island, which inevitably lead to a slowdown of the circulation in the North Atlantic Ocean.
Increased surface melting and modest snow accumulation has been a problem since the 1970s, however, since 2009 the problem has been greatly exacerbated. In fact, last July the National Oceanic and Atmospheric Administration (NOAA) reported that the Greenland melt area covered more than half of its ice sheet for the first time since July 2012.
Sea level rise is already "becoming very conspicuous and it's going to be bad. It's happening faster and faster as my Rutgers colleagues have been measuring," Francis added. "This change is accelerating."
Blocking-high pressure systems over Greenland usually form when a lot of warm air is in the Arctic. This Arctic warmth then weakens the jet stream, which typically flows west to east, allowing it to meander more to the north and south, Francis explained.
The jet stream can take "such a big northward swing that it actually kind of breaks off and forms a closed circulation," she said, adding that this makes blocking highs persistent and hard to forecast. So far this year, the Arctic has seen unusually warm temperatures and reports indicate sea ice cover is at a record low.
"Whenever there's a big melt year in Greenland, on the surface anyway, it's usually because there's either a blocking high or a large northward swing in the jet stream and both of those things tend to be long-lived features in the circulation," Francis concluded.
Their findings were recently published in the Journal of Climate.