Saturday, May 28, 2016

Arctic Sea Ice Goes Far Beyond Record Low Extent for May

By: Bob Henson , 4:01 PM GMT on May 20, 2016

The sea ice that coats the Arctic Ocean each winter and erodes each summer is going through its most depleted spring since modern observing began. The Danish Meteorological Institute reported the lowest sea ice extent of any April in the Arctic’s 38-year-long satellite record. As luck would have it, the primary satellite sensor used by the National Snow and Ice Data Center (NSIDC) for extent measurement began producing spurious data in April. A similar microwave imager from another satellite is now in the process of being intercalibrated to ensure consistency of the long-term record. Even with that caveat, it’s clear that the unusually rapid ice loss from April is steaming ahead. NSIDC’s Mark Serreze confirmed in an email that the 2016 Arctic sea ice extent is indeed at record-low levels for May, as implied by Figures 1 and 2. Different agencies use different algorithms to measure sea ice extent, but the slight variations that result do not affect the big picture.


This year’s hasty ice retreat has been fueled by incredibly mild temperatures across the Arctic during much of the winter and spring--a byproduct of El NiƱo atop longer-term warming from human-produced greenhouse gases. At Barrow, Alaska, every day since January 1 has been above average except for January 22, February 6, and a stretch from March 28 to April 3. Alaska’s Climate Division 1, which covers the North Slope, is having its warmest year to date by far (see Figure 3), with the January-to-April average of 2.7°F beating the previous record (–1.4°F, from 2014) by an eye-popping 4.1°F. Another red-letter data point: snow cover disappeared from the open tundra at the NOAA Barrow Observatory on May 13.


Another downside of premature snow cover loss is the potential for early-season wildfire across the far north. A prime example is Canada’s disastrous Fort McMurray fire, which exploded in early May as record heat swept over a snowless landscape. Although the fire still surrounds the city, some 85 to 90 percent of Fort McMurray’s structures were saved, and residents may be able to return beginning in early June. Media interest in the event has waned in recent days, but the fire continues to rage, with a new burst of growth this week. On Thursday, the fire covered some 1.2 million acres--twice the size of Rhode Island--and was beginning to extend into Saskatchewan. As noted by blogger Robert Scribbler, this fire already has spanned more area than all of Alberta’s fires in 2015 combined. Soot from the Fort McMurray fire, and from major wildfires burning across parts of Siberia, could exacerbate the loss of sea ice by falling atop the ice and darkening the surface, thus increasing its ability to absorb sunlight.


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