by Neven Acropolis
Whoever said watching the Arctic during the melting season is boring, needs to put his glasses on. After a record low reflectivity of the Greenland ice sheet (with accompanying floodings on the west coast of Greenland), the calving of another enormous iceberg from Petermann Glacier, and the general rapid decline of Arctic sea ice despite adverse weather patterns, we can now add to the 2012 melting season bonanza the appearance of a cyclone the likes of which are rarely seen in winter, let alone in summer.
The storm came in from Siberia, intensified and then positioned itself over the central Arctic, reaching sea level pressures of below 965 mb in the storm’s centre, engendering 20 knot winds and 50 mph wind gusts:
The storm is now losing its strength and dissipating, but its effect on the sea ice has been enormous so far. In this phase of the melting season when decline starts to slow down, large swathes of sea ice just disappear from one day the next, and the next, and the next (which is why I refer to it as flash melting). It can clearly be seen on this animation of sea ice concentration maps that are updated daily on the Cryosphere Today website, showing the sea ice decline of the past couple of days:
Although technically not all of the ice that disappears on these maps is completely melted (some of it doesn’t get picked up by satellite sensors due to clouds and waves submerging ice floes), the gale-force winds displace and break up ice floes, and churn the waters below causing warmer, saltier layers under the thin film of fresh water to mix upwards and melt the ice some more from the bottom. This storm is the worst thing that could have happened to an already weakened and dispersed ice pack.
One development on these sea ice concentration maps that stand out particularly, is the detachment of a large swathe of ice floes from the main ice pack. I’ve never seen such a thing before, and I wouldn’t be surprised if it is unprecedented in the satellite era. But I guess that is what highly unusual Arctic summer storms can lead to.
The effects on the ice pack are also staring to get picked up on sea ice area and extent graphs. The most remarkable decline can be seen on this sea ice extent graph from the Danish Meteorological Institute: