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Friday, July 20, 2012

Jeff Masters: Record warmth at the top of Greenland Ice Sheet

by Jeff Masters, WunderBlog, July 18, 2012

The coldest place in Greenland, and often the entire Northern Hemisphere, is commonly the Summit Station. Located at the top of the Greenland Ice Sheet, 10,552 feet (3,207 meters) above sea level, and 415 miles (670 km) north of the Arctic Circle, Summit rarely sees temperatures that rise above the freezing mark. In the 12-year span 2000-2011, Summit temperatures rose above freezing only four times, according to weather records researcher Maximiliano Herrera. But remarkably, over the past week, temperatures at Summit have eclipsed the freezing mark on five days, including four days in a row from July 11 to 14. There are actually three weather stations located at the location -- Summit, Summit-US, and Summit AWS. The highest reliable temperature measured at any of the three stations is now the 3.6 °C (38.5 °F) measured on Monday, July 16, 2012, at Summit-US. A 4.4 °C reading at Summit in May 2010 is bogus, as can be seen by looking at the adjacent station. Similarly, a 3.3 °C reading from June 2004 is also bad. Records at Summit began in 1996.

Video 1. A 20-ton tractor attempting to repair a bridge washed out by the raging Watson River on July 11, 2012, in Kangerlussauaq, Greenland, gets washed downstream. The driver escaped unharmed. Image taken from an article,Warm air over the ice sheet provides great drama in Greenland, at the Danish Meteorological Institute's web site.

Record heat leads to major flooding in Greenland
The record heat has triggered significant melting of Greenland's Ice Sheet. According to the Arctic Sea Ice Blog, on July 11, glacier melt water from the Russell Glacier flooded the Watson River, smashing two bridges connecting the north and south of Kangerlussuaq (Sønder Strømfjord), a small settlement in southwestern Greenland. The flow rate of 3.5 million liters/sec was almost double the previous record flow rate.The latest forecast for Summit calls for cooler conditions over the coming week, with no more above-freezing temperatures at Summit.

Another huge iceberg calves off of Greenland's Petermann Glacier
A massive ice island two times the size of Manhattan and half as thick as the Empire State Building calved off of Greenland's Petermann Glacier on Monday, July 16, 2012. According to Andreas Muenchow, associate professor of physical ocean science and engineering at the University of Delaware's College of Earth, Ocean, and Environment in his Icy Seas blog, the break-off point has been visible for at least 8 years in satellite imagery, and has been propagating at 1 km/year towards Nares Strait. The same glacier calved an iceberg twice as big back on August 4, 2010 -- the largest iceberg observed in the Arctic since 1962. The freshwater stored in that ice island could have kept the Delaware or Hudson rivers flowing for more than two years, or kept all U.S. public tap water flowing for 120 days. “While the size is not as spectacular as it was in 2010, the fact that it follows so closely to the 2010 event brings the glacier’s terminus to a location where it has not been for at least 150 years,” Muenchow said in a university press release. “Northwest Greenland and northeast Canada are warming more than five times faster than the rest of the world, but the observed warming is not proof that the diminishing ice shelf is caused by this, because air temperatures have little effect on this glacier; ocean temperatures do, and our ocean temperature time series are only five to eight years long — too short to establish a robust warming signal.”

Figure 1. The calving of a massive 46 square-mile iceberg two times the size of Manhattan from Greenland's Petermann Glacier on July 14-18, 2012, as seen using MODIS satellite imagery. Image credit: NASA.

Figure 2. Look familiar? Two years ago, a 100-square-mile ice island broke off the Petermann Glacier. It was the largest iceberg in the Arctic since 1962. Image taken by NASA's Aqua satellite on August 21, 2010. Image credit: NASA. I've constructed a 7-frame satellite animation available here that shows the calving and break-up of the Petermann Glacier ice island. The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart. The images were taken by NASA's Aqua and Terra satellites.

Related posts

Unprecedented May heat in Greenland; update on 2011 Greenland ice melt

Greenland update for 2010: record melting and a massive calving event

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