Sudden Arctic Cyclone Churns Through Beaufort Sea Ice

Sudden Arctic Cyclone 2013 over Beaufort Sea. Image source: DMI

In a new incarnation of the Warm Storm event that has increasingly come to impact summer Arctic sea ice, a rapidly intensifying low pressure system formed Tuesday over the Beaufort, tracking directly through a large section of vulnerable ice and moving on toward the Canadian Archipelago. At its most intense the storm dropped to 977 millibars but has weakened slightly today to 980 millibars. The storm is expected to continue slowly weakening through today and tomorrow until finally fading by late Saturday or early Sunday.

Though strong, this storm is expected to be brief and is likely to not have the same impacts seen during the Great Arctic Cyclone of 2012. That storm approached the Arctic as an already well-developed system. Packing winds in excess of 60 miles per hour, it had the opportunity to rile a large section of open water and then fling waves as high as 10 feet up against the ice pack. Though this particular storm has hosted gale force winds, they have mostly blown parallel to the ice edge and did not have the same opportunity to develop a longer fetch over open water. It is also worth noting that the Great Arctic Cyclone lasted for about two weeks while this most recent Sudden Arctic Cyclone is likely to last for only about four to five days. So ongoing effects are likely to be limited.

All that said, this storm should have some impact. Already, an increasing number of slats of open water are visible through large sections of the Beaufort and the ice edge appears to have been torn at like a large swatch of tissue paper might act when forcibly twisted. The ice this year is particularly thin and slushy, making it subject to much more rapid motion and deformation. So we are already seeing such effects.

The below image shows a section of central Beaufort sea ice just after the storm center passed. Note the cracked and more diffuse condition of the ice.

Sea ice traumatized by Sudden Arctic Cyclone at 80N and 150W. Image source: NASA

In addition to the impacts described above, warmer air and constant sunlight over the Beaufort have likely provided a number of reservoirs of heat energy for the storm to tap to melt and thin the ice. Cyclonic pumping will be able to dredge warmer, saltier waters from the bottom layer even as surface churning will mix both ice and water warmed by these cyclonic forces. Brine channels within the ice are more likely to activate now that summer has had the opportunity to soften up the ice, pushing an increasing number of patches above the critical -5 C threshold.

CICE model runs do show a substantial thinning of Beaufort sea ice over the next few days even as the thick sea ice remaining near the Canadian Archipelago is both shoved into narrow island channels and ablated toward the Fram Strait between Greenland and Svalbard. Note the shift of light blue to dark blue, and yellow and red to green in many regions indicating significant predicted thinning in response to storm conditions. The two meter ice line is seen to rapidly retreat into the Beaufort from near the Canada/Alaska coast and also from the Chukchi, East Siberian, and Laptev Seas. Meanwhile, the four meter ice line is slammed directly against the Canadian Archipelago as thicker ice is slammed against shores or jammed into the island channels:

CICE model run. Image source: US Navy.

In summary, we can expect these effects from this, rather strong, storm. Not likely to be as pronounced as GAC 2012 nor as ongoing as PAC 2013 (whose scars are still visible in the large region of melt in a wide triangle from the Laptev toward the North Pole). But this Sudden Arctic Cyclone will certainly leave its own mark on the 2013 melt season.

Posted by robertscribbler on July 25, 2013

https://robertscribbler.wordpress.com/2013/07/25/sudden-arctic-cyclone-churns-through-beaufort-sea-ice/