Rain showers in Greenland indicate climate change

Something extraordinary happened last Saturday at the highest point of the Greenland Ice Cap, two miles in the sky and over 500 miles ab...


Something extraordinary happened last Saturday at the highest point of the Greenland Ice Cap, two miles in the sky and over 500 miles above the Arctic Circle: it rained for the first time.

Rain at a research station – not just a few drops or a drizzle, but a stream for several hours, as temperatures slightly exceeded freezing – is another disturbing sign of a change in the Arctic, which is heating up faster than any other region on the planet. .

“It’s amazing, because this writes a new chapter in the Greenland book,” said Marco Tedesco, a researcher at the Lamont-Doherty Earth Observatory at Columbia University. “It’s really new.”

At the station, which is called Summit and is busy year round under the auspices of the National Science Foundation, there has been no evidence of rain since sightings began in the 1980s. And computer simulations do show. no evidence going even further back, said Thomas Mote, a climatologist at the University of Georgia.

Above-freezing conditions at Summit are almost as rare. Prior to this century, ice cores were shown to have occurred only six times in the past 2,000 years, wrote Martin Stendel, senior researcher at the Danish Meteorological Institute, in an email message.

But above freezing temperatures have now occurred at the peak in 2012, 2019 and this year – three times in less than 10 years.

The Greenland ice sheet, which is up to two miles thick and covers around 650,000 square miles, has lost more ice and contributed more to sea level rise in recent decades as Earth has warmed due to anthropogenic emissions of carbon dioxide and other heat-trapping gases.

The surface of the ice sheet is increasing in mass each year because the accumulation of snow is greater than the surface melt. But overall, the slick loses more ice by melting where it meets the ocean and breaking up icebergs. On average over the past two decades, Greenland has lost over 300 billion tonnes of ice each year.

This year will likely be an average year for surface buildup, said Dr Stendel, who is also the coordinator of Polar portal, a website that disseminates the results of Danish research on the Arctic. Heavy snowfall at the start of the year suggested it could be an above-average build-up year, but two periods of warming in July and another in early August changed that by causing widespread surface melting.

The warming that accompanied last Saturday’s rain also caused more than 50 percent of the ice sheet to melt.

Dr Mote said these melting episodes were each “one-time” events. “But these events seem to be happening more and more frequently,” he said. “And it tells the story that we are seeing real evidence of climate change in Greenland.”

Last Saturday marked the first time since satellite monitoring began in 1979 that melting occurred over more than half of the surface in mid-August, Dr Mote said. Normally, the melting peak occurs in mid-July, like in 2012, when there was a huge melting event.

“By the time you get to mid-August, you usually see a rapid decline in melting activity and a drop in temperature,” he said.

Dr Tedesco said rain at the top will not directly contribute to sea level rise, as the water flows through the ice rather than the ocean. “But if it happens at the top, the effect at low altitude will be more violent,” he said. “And that ice is actually going to the ocean.”

Dr Tedesco called the rain at the top “worrisome” because it shows that even a slight warming can have an effect in the region.

“Half a degree of warming can really change the state of the Arctic because you can go from freezing to liquid,” he said. “This is exactly what we are seeing.”

Last Saturday’s rain and melt occurred when the jet stream, instead of flowing normally from west to east, plunged south over northeastern Canada. This brought low pressure air to warmer waters, where it captured heat and humidity.

The jet stream then looped north, bringing this air to southwest Greenland from where it swept through the ice cap. The warm air and even the moisture-laden clouds themselves caused peak temperatures to rise and precipitation in the form of rain rather than snow, Dr Mote said.

Some scientists have linked jet stream disturbances like this, often referred to as ‘ripple’, to climate change in the Arctic, although this is still the subject of debate. But they do occur and also create blocking patterns that can block high pressure air over an area.

This is what happened during the first episodes of melting this summer. The high pressure air that stalled over the ice cap led to clear skies that allowed more sunlight to reach the surface, melting more snow.

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Newsrust - US Top News: Rain showers in Greenland indicate climate change
Rain showers in Greenland indicate climate change
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