Late-season snow cover also shrinking dramatically in northern hemisphere
FRISCO — Warm June temperatures across much of the Arctic may have set the stage for a big sea ice meltdown during the next few weeks, federal ice trackers said as they released their latest monthly update last week.
The Arctic sea ice extent for June 2015 was the third lowest on record, and June snow cover was the second-lowest, according to the National Snow & Ice Data Center report, which measured an average sea ice extent of about 4.24 million square miles for the month, which is 355,200 square miles below the 1981 to 2010 long-term average.
July is the warmest month in the northern hemisphere, so the melting will quicken the next several weeks, especially if warm conditions continue. Over the Kara Sea, air temperatures ranged from 4 to 9 degrees Fahrenheit above average, and over the Siberian Sea, temperatures were about 4 to 5 degrees Fahrenheit above average.
The continued meltdown of the Arctic was also highlighted by the low June snow cover in the northern hemisphere — the second-lowest on record, at 2.10 million square miles, according to the Rutgers Global Snow Lab. The snow cover extend was especially low over Alaska and western Canada after a warm and dry winter. The region is now experiencing record wildfires.
But even through spring snowcover has been on a steep decline in the northern hemisphere, climate scientists say precipitation in the Arctic will increase through the 21st century. More moisture in the atmosphere will bring increased poleward transport and convergence of moisture, with the most pronounced effects in Autumn.
The NSDIC report cites a recent study showing that more open water in the Barents and Kara seas has indeed led to an increase in autumn snowfall over Eurasia, which helps account for a decadal upward trend in winter (but not spring) snow cover extent across the northern hemisphere.
At the other end of the globe, sea ice extent in Antarctica is once again near a record high level. Satellite observations show unusually extensive sea ice growth along the western side of the Antarctic Peninsula.
But the recent record-level Antarctic sea ice extent is not making up for losses in the Arctic. A recent NASA-led study showed that, overall, the planet has been losing sea ice for the past few decades. Between 1996 to 2013, the loss was about 19,500 square miles per year — larger than the states of Vermont and New Hampshire combined.