Tuesday, July 23, 2013

Snow and Arctic sea ice extent plummet suddenly as globe bakes

from The Washington Post

Temperature difference from average during June around the globe (NASA)

NOAA and NASA both ranked June 2013 among the top five warmest (NOAA fifth warmest, NASA second warmest) Junes on record globally (dating back to the late 1800s). But, more remarkable, was the incredible snow melt that preceded the toasty month and the sudden loss of Arctic sea ice that followed.

NH snow cover extent difference from average April to May (NOAA)

The amazing decline in Northern Hemisphere snow cover during May is a story few have told, but is certainly worth noting. In April, hefty Northern Hemisphere snow cover ranked 9th highest on record (dating back to 1967), but then turned scant, plummeting to third lowest on record during May. Half of the existing snow melted away.

“This is likely one of the most rapid shifts in near opposite extremes on record, if not the largest from April to May,” said climatologist David Robinson, who runs Rutgers University Global Snow Lab.

The snow extent shrunk from 12.4 million square miles to 6.2 million square miles in a month’s time. By June, just 2.3 million square miles of snow remained in the Northern Hemisphere (a decline of 63 percent from May), third lowest on record.

“In recent years it hasn’t seemed that unusual to have average or even above average winter snow extent rapidly diminish to below average values come spring,” Robinson said.

Northern Hemisphere spring snow cover is in the midst of long-term free fall, similar to its relative, summer Arctic sea ice extent.

You may recall, late last summer the Arctic sea ice extent dropped to its lowest level on record, 49 percent below the 1979-2000 average.

Temperature difference from normal over the high latitude Northern Hemisphere over first 10 days of July (National Snow and Ice Data Center)

It’s not clear if 2013 levels will match 2012′s astonishing record low, but – with temperatures over the Arctic Ocean 1-3 degrees above average – the 2013 melt season has picked up in earnest during July.

“During the first two weeks of July, ice extent declined at a rate of 132,000 square kilometers (51,000 square miles) per day. This was 61% faster than the average rate of decline over the period 1981 to 2010 of 82,000 square kilometers (32,000 square miles) per day,” the National Snow and Ice Data Center writes on its website.

Despite this rapid ice loss, the current mid-July 2013 sea ice extent is greater than 2012 at the same time by about 208,000 square miles NSIDC says.

2013 sea ice extent (blue line) compared to average (black line) and record (dahsed green line). (National Snow and Ice Data Center)

Will 2013 close the gap? That depends on the weather, as the Arctic Sea Ice blog explains:

….the amount of easy-to-melt ice is starting to run out. Even though this year’s ice pack consists of a record amount of first-year ice [which melts most readily], the weather still plays an important role. . . .

. . . there’s no telling what could happen if the weather is very conducive to melting/compacting/transport for a week or two….

Jason Samenow is the Capital Weather Gang's chief meteorologist and serves as the Washington Post's Weather Editor. He earned BA and MS degrees in atmospheric science from the University of Virginia and University of Wisconsin-Madison.

check out all the graphs here at the original post in the Washington Post

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