The latest report from the National Snow & Ice Data Center reports that “Arctic sea ice extent during the first two weeks of August continued to track below 2007 record low daily ice extents.
“As of August 13, ice extent was already among the four lowest summer minimum extents in the satellite record, with about five weeks still remaining in the melt season.
“Sea ice extent dropped rapidly between August 4 and August 8. While this drop coincided with an intense storm over the central Arctic Ocean, it is unclear if the storm prompted the rapid ice loss. Overall, weather patterns in the Arctic Ocean through the summer of 2012 have been a mixed bag, with no consistent pattern.”
The NSIDC reported that as of August 13 Arctic sea ice extent “was 5.09 million square kilometers (1.97 million square miles). This is 2.69 million square kilometers (1.04 million square miles) below the 1979 to 2000 average extent for the date, and is 483,000 square kilometers (186,000 square miles) below the previous record low for the date, which occurred in 2007.”
In addition the report said the “average pace of ice loss since late June has been rapid at just over 100,000 square kilometers (38,000 square miles) per day. However, this pace nearly doubled for a few days in early August during a major Arctic cyclonic storm.”
The NSIDC compared conditions over the Arctic in 2007 and this year. It described the summer of 2007 as presenting a “persistent pattern of high pressure,” which covered “the central Arctic Ocean and a pattern of low pressure was over the northern Eurasian coast.”
The summer of 2012, however, “has been characterized by variable conditions. Air temperatures at the 925 hPa level (about 3000 feet above the ocean surface) of 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2012 average have been the rule from central Greenland, northern Canada, and Alaska northward into the central Arctic Ocean.
“Cooler than average conditions (1 to 2 degrees Celsius or 1.8 to 3.6 degrees Fahrenheit) were observed in a small region of eastern Siberia extending into the East Siberian Sea, helping explain the persistence of low concentration ice in this region through early August.
“A low pressure system entered the Arctic Ocean from the eastern Siberian coast on August 4 and then strengthened rapidly over the central Arctic Ocean. On August 6 the central pressure of the cyclone reached 964 hPa, an extremely low value for this region. It persisted over the central Arctic Ocean over the next several days, and slowly dissipated. The storm initially brought warm and very windy conditions to the Chukchi and East Siberian seas (August 5), but low temperatures prevailed later.”
The low pressure, which produced the storm, further affected the already highly complex weather patterns over the Arctic. The report said that “coincident with the storm, a large area of low concentration ice in the East Siberian Sea (concentrations typically below 50 percent) rapidly melted out.
“On three consecutive days (August 7, 8, and 9), sea ice extent dropped by nearly 200,000 square kilometers (77,220 square miles). This could be due to mechanical break up of the ice and increased melting by strong winds and wave action during the storm. However, it may be simply a coincidence of timing, given that the low concentration ice in the region was already poised to rapidly melt out.”
Source: National Snow & Ice Data Center