Scientists at the US National Snow and Ice Data Center (NSIDC) say that sea ice extents in the Arctic are very low for this period. They say that increasing amounts of ice were lost during the middle of July, while open waters could be observed throughout the Kara Sea and the Barents Sea.
Typically, this number and sizes of open water regions only start to become visible in September. In other words, sea-based ice began melting earlier on in the year in 2012 than the long-term average would suggest as normal.
Two days ago, on July 23, the total sea ice extent at the North Pole was 7.32 million square kilometers (2.82 million square miles), just 0.10 million square kilometers (0.04 million square miles) above the record-lowest amount ever recorded on the same day, which occurred in 2011.
NSIDC investigators say that the Barents Sea, the Kara Sea, and the Laptev Sea are the most affected areas. Most of the ices that were supposed to be covering these bodies of water have now retreated all the way to the edge of the multi-year ice sheets.
“The first part of July was once again dominated by high sea level pressure over the Beaufort Sea, combined with low sea level pressure over Siberia and Alaska. […] This pressure pattern tends to promote above-average temperatures and enhances ice transport out of the Arctic through Fram Strait,” the team says.
“The timing of seasonal melt onset, which can be estimated from satellite passive microwave data, plays an important role in the amount of ice that melts each summer. Unusually early melt onset means an early reduction in the surface albedo, allowing for more solar heating of the ice,” experts add.
This means that more melt ponds can develop, which promote even more rapid ice melt. With the exception of the Bering Sea and the East Greenland Sea, the melt season began in all areas of the Arctic faster in 2012 than between 1979-2000.
For its studies, NSIDC uses data from the Special Sensor Microwave Imager (SSM/I) and the Special Sensor Microwave Imager/Sounder (SSMIS) instruments, as well as the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) instrument, all aboard special satellites.
“Low ice concentrations mean a low surface albedo, allowing for more of the sun’s energy to be absorbed, melting even more sea ice. This makes the multiyear ice in the Beaufort and Chukchi seas vulnerable to melting out this summer,” the new report concludes.