Following on a record rate of retreat for Arctic sea ice in June, as of July 17 sea ice area in the Arctic has fallen below 5 million square kilometers (nearly 2 million square miles), a decline reached earlier in the melt season than at any time in recorded history. The ice extent shrank from 6 million square kilometers to less than 5 million in just nine days.
Chart from National Snow & Ice Data Center showing arctic sea ice extent
The 2012 sea ice area fell from its maximum to below 5 million square kilometers in only 110 days, the quickest decline in the 33-year record. For nine of those years, the area never made it below 5 million square kilometers. In the years the ice dipped below 5 million, it took on average 159 days from maximum. The previous record was only last year, when the decline took 135 days.
Of course, sea ice area and extent typically decline during the short Arctic summer, from as much as 15 million square kilometers (area) in late spring to 3 million at the start of autumn. The current Arctic sea ice area is now 2 million square kilometers below the 1979-2008 mean, a full month earlier than the previous earliest record in 2007.
Unprecedented Greenland ice sheet melt
Satellite images over Greenland this month indicate surface ice melted over a larger area of the continent than at any time in the 30-year satellite record. According to the data, 97 percent of the ice sheet is estimated to have thawed at some point by the middle of July. It is still too early to determine how much of an affect the current surface thaw will have on overall ice loss and sea level rise.
“The Greenland ice sheet is a vast area with a varied history of change,” said Tom Wagner, NASA’s cryosphere program manager in Washington. “This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story. Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system.”
On July 11, the recorded temperature on Greenland’s Summit Camp was 2.2 degrees Celsius (almost 36 degrees Fahrenheit). Summit Camp is located at an elevation of 3200 meters (10,498 ft.) the highest point of the Greenland ice sheet.
Main image credit: public domain images; Arctic sea ice decline chart credit: National Snow & Ice Data Center