Satellite image from NASA acquired February 23, 2013.
New images of 2013's Arctic sea ice mega-fracture have been posted on NASA's website. Sea ice fractures are not uncommon, though, according to NASA, the extent of this one is. Two things have combined this year to create the mega-fracture:
1) Arctic sea ice is not what it used to be. It is becoming thin and fragile, whereas thick, multi-year ice (ice that is around for many years and is much more stable) has declined. Arctic sea ice extent has plummeted since 1979, and reached an all-time low in September 2012. According to the National Snow and Ice Data Center, through 2013, February sea ice extent has declined at a rate of 2.9% per decade compared to the long-term average. This represents an overall reduction of more than 606,000 square miles from 1979 to 2013, which is equivalent to more than twice the area of the state of Texas. Scientific consensus points to global warming from fossil fuel emissions as the culprit of the Arctic's decline.
2) In February and March, the weather pattern has been consistently offshore and unfavorable for the sea ice, pushing the ice away from shore. These weather patterns are not uncommon. The difference is that these days, the fragile ice cannot endure the stress, and fractures more than it would have in previous years.
The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this view of extensive sea-ice fracturing off the northern coast of Alaska. The event began in late-January and spread west toward Banks Island throughout February and March 2013. Source: NASA Earth OBservatory on YouTube.
Animation of the ice fracture using satellite AVHRR data, from the Arctic Sea Ice blog on NSIDC.
The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this view of extensive sea-ice fracturing off the northern coast of Alaska. The event began in late-January and spread west toward Banks Island throughout February and March 2013.
Visualizations of the Arctic often give the impression that the ice cap is a continuous sheet of stationary, floating ice. In fact, it is a collection of smaller pieces that constantly shift, crack, and grind against one another as they are jostled by winds and ocean currents. Especially during the summer—but even during the height of winter—cracks—or leads—open up between pieces of ice.
That was what was happening on the left side of the animation (below) in late January. A high-pressure weather system was parked over the region, producing warmer temperatures and winds that flowed in a southwesterly direction. That fueled the Beaufort Gyre, a wind-driven ocean current that flows clockwise. The gyre was the key force pulling pieces of ice west past Point Barrow, the northern nub of Alaska that protrudes into the Beaufort Sea.
"A fracturing event in this area is not unusual because the Beaufort Gyre tends to push ice away from Banks Island and the Canadian Archipelago," explained Walt Meier of the National Snow & Ice Data Center (NSIDC). "Point Barrow can act like a 'pin point' where the ice catches and fractures to the north and east."
In February, however, a series of storms passing over central Alaska exacerbated the fracturing. Strong westerly winds prompted several large pieces of ice to break away in an arc-shaped wave that moved progressively east. By the end of February, large pieces of ice had fractured all the way to the western coast of Banks Island, a distance of about 1,000 kilometers (600 miles).
The data used to create the animation came from the longwave infrared (thermal) portion of the electromagnetic spectrum, so the animation illustrates how much heat the surface was emitting as VIIRS surveyed the area. Cooler areas (sea ice) appear white, while warmer areas (open water) are dark. The light gray plume near the cracks is warmer, moister air escaping from the ocean and blowing downwind. Clouds do not show up well in the VIIRS thermal band, so the storms that fueled the fracturing are not readily visible.
While fracturing events are common, few events sprawl across such a large area or produce cracks as long and wide as those seen here. The age of the sea ice in this area was one of the key reasons this event became so widespread. “The region is covered almost completely by seasonal or first-year ice—ice that has formed since last September,” said Meier. “This ice is thinner and weaker than the older, multi-year ice, so it responds more readily to winds and is more easily broken up.”
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