Posted by: Dr Churchill | July 27, 2012

Petermann’s loss

 

The news that an unusually widespread melt occurred in Greenland during mid-July, when 97 percent of the Greenland ice sheet — including normally frigid high-elevation areas — experienced some degree of melting, has made international headlines, and for good reason. Such a widespread melt event has not occurred there since at least 1889, and may be yet another sign of the consequences of manmade climate change.   Greenland’s massive ice sheet drains slowly to the sea, but until the last decade or two, the drainage was balanced by new snow that fell every winter. Not anymore, though: thanks to rising global temperatures. Greenland has begun shedding ice at a prodigious rate, a major factor in the sea level rise that poses a greater threat to life and property with every passing year.

Usually, glacial ice enters the sea in chunks the size of buildings, but satellite images are showing the Petermann Glacier, in northwest Greenland, has let go of a slab of ice twice the size of Manhattan.

Now that Petermann has let go of this much ice, the vast new ice island is floating toward the Nares Strait, a body of water that separates the Arctic Ocean from Baffin Bay. The breakup is probably caused by rising air and ocean temperatures, which had until recently spared the northernmost parts of Greenland.

It isn’t the first time the Petermann glacier has lost so much ice at once: back in 2010, an even bigger piece — as big as four Manhattans put together — broke free. And last year, glaciologist Jason Box of the Byrd Polar Research Center at Ohio State University’s told the New York Times that another big piece was set to go.

As for what led to this unusual event, it was set off by unusually mild weather conditions that have occurred more frequently in that region during recent summers. According to NASA, a series of High Pressure centers, or “ridges” in the upper atmosphere, have set up over Greenland since May, NASA said, pumping mild air into the area and resulting in less cloudiness than average. The ridge, or “heat dome,” is similar to the weather patterns that have caused record heat in much of the U.S. this summer.

“This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate,” NASA reported. At the Summit station, the high temperature on July 11 was 36°F, which was warm enough to thaw snow and ice at that high altitude.

Sea surface temperatures have also been running much above average along the western coast of Greenland, which likely contributed to the loss of a massive chunk of ice from the Petermann Glacier in mid-July.

 

The Petermann Glacier photographed by NASA.

 

As the Petermann Glacier and other tidewater glaciers (that is, glaciers that reach the sea) lose ice at their seaward ends, the uphill parts can slide more easily — so even if the new ice island doesn’t add much to the rising seas, it could eventually make the Petermann a significant contributor, as glaciers in the south of Greenland already are.

That also goes for glaciers much further to the south — glaciers at the other end of the world, in Antarctica.

 

Recent studies have shown that warmer ocean temperatures could soon be causing significant ice loss from the ice sheets that blanket the South Pole.

 

In terms of the importance and significance of an entire ice sheet melt event, it gets you thinking the future of the Greenland Ice Sheet.

Is there a welcome future there?

 

 

Yours,

Pano

PS:

The last time it was as warm as it is now, about 120,000 years ago, sea level was up to 29 feet higher than it is today. And for it to have gone that high, Antarctic melting must have been part of the mix.

No one knows for sure what that means for our own future. But if the air, the atmosphere, the land and the water all keep getting warmer, and the ice keeps plopping into the sea, it can’t be a harbinger of good tidings…

 


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