Greenland ice melts four times faster than expected – what that means



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A new study warns that Greenland ice melts faster than previously thought. But perhaps the biggest surprise is that most of the loss of ice comes from the fast ice sheet, not the Greenland glacier.

The new study, which was published January 21 at Proceedings of the National Science Academy, found that the largest continuous loss of ice from early 2003 to mid-2013 came from the southwestern region of Greenland, which most did not have large glaciers.

Greenland, the largest island in the world, appears to have reached a tipping point around 2002-2003 when ice loss accelerated, said lead author Michael Bevis, a geographer at Ohio State University. In 2012 the annual ice loss was "unprecedented" at a rate nearly quadrupled in 2003, Bevis said in an interview.

Most of this accelerated ice melt comes from southwest Greenland, a part of the island that is not known to lose ice quickly. Previously, the scientific focus was in the southeastern and northwestern regions of Greenland, where large glaciers drew chunks of ice the size of icebergs into the Atlantic Ocean.

"We know we have one big problem with the increasing rate of release of ice by several large glacier outlets," said Bevis. "But now we recognize the second serious problem: The more mass of ice will go as melt water, like the river flowing into the sea.

Data from the NASA GRACE satellite and GPS stations scattered around the coast of Greenland show that between 2002 and 2016, Greenland lost around 280 billion tons of ice per year. The average annual melting of ice is enough to cover the entire state of Florida and New York that sink deep in disbursement, and sink Washington, D.C. and one or two other small countries.

"This will cause additional sea level rise. We see the ice sheet reaching a critical point," Bevis said.

The Greenland ice sheet is 10,000 feet thick in several places and contains enough ice to raise the sea level 23 feet (7 meters). In the 20th century, Greenland has lost around 9,000 billion tons of ice in total, contributing 25 millimeters of sea level rise. (It takes around 360 billion tons of ice to produce one millimeter of global sea level rise.)

However, Greenland is dwarfed by the Antarctic ice sheet, which can raise sea level 57 meters if it completely melts. Alarmingly, Antarctica is also experiencing accelerated liquefaction, ice loss is six times more than four decades ago, a January 14 study reported. The ice loss averages 252 billion tons per year over the past decade.

That is the same story for western North American glaciers – a fourfold loss of ice since the early 2000s to 12.3 billion tons per year, a recent study revealed.

What causes liquefaction?

Global warming with a temperature of only 1 degree C is the main driver behind the massive ice crisis of the world. In Greenland, researchers found that global warming, coupled with the negative phase of the North Atlantic Oscillation, caused a rapid melting of the ice sheet during the summer. North Atlantic Oscillation (NAO) is an irregular natural change in atmospheric pressure and brings warm and sunny summer weather to the west side of Greenland while in a negative phase. Before 2000, this did not cause significant melting of ice, said Bevis, but since then the negative phase of NAO resulted in a large increase in ice melting.

This is analogous to the El NiƱo-Southern Oscillation (ENSO) cycle and coral bleaching, he said. In 1997-98, a strong El Nino event caused massive bleaching of most of the world's tropical reefs. Previously, such events only had a small impact on coral reefs, but in 1997 climate change warmed tropical seawater to the point where any additional warming because El Nino was too much for corals to survive. Now every time an El Nino reef suffers.

The Bevis study shows southwest Greenland is where ice sheets are most vulnerable to atmospheric cycles such as El Nino which is superimposed on a warming trend, said Jason Box, a geologist at the Danish Geological Survey and Greenland. And it's clear that more overall loss of ice comes from the surface than the glaciers that end the sea, Box said.

What is needed to melt the Greenland ice sheet is the surface temperature of 1 C and sunlight. "It used to rarely get temperatures above 0 degrees on the ice sheet, but not anymore," Bevis said. And every degree above 1 C doubles the amount of melting ice.

What happens next?

Without acting immediately to dramatically reduce the burning of fossil fuels that increase global temperatures, most or all of Greenland's ice can melt, raising the sea level 23 feet, warns Richard Alley, a glaciologist at Penn State. This will happen for centuries. However, there is a warming threshold that can be traversed in decades or less and, if it exceeds long enough, the destruction of Greenland will not be changed, Alley said.

The residents of Greenland Village were evacuated as Giant Iceberg Floats By

Another major concern is that all this melt water slows down the Gulf Stream which brings warm water from the equator to the North Atlantic and cold water drops into the deep sea. The Gulf Stream, better known as Atlantic meridional overturning (AMOC) circulation, is why Western Europe has moderate weather. Last year, researchers reported in the journal Natural that AMOC has decreased in strength by 15 percent since the mid-20th century.

Meteorologists now believe this slowdown is related to the recent summer heat wave in Europe. A joint writer Natural Research, Stefan Rahmstorf of the Potsdam Institute for Research on Climate Impacts in Germany, linked slowing to the huge volume of meltwater from Greenland. "I think it's happening … And I think that's bad news," he told Washington Post.

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