Arctic cyclone

First Named Arctic Cyclone to Deliver Powerful Blow to Sea Ice?

robertscribbler,

22 July, 2013

The weather models are all in agreement, an Arctic Cyclone is predicted to form over the Beaufort and Chukchi Seas tonight and tomorrow, then strengthen to around 980 millibars as it churns through a section of thin and broken sea ice. The storm is predicted to last at least until Saturday and is expected to deliver gale force winds over a broad swath of thinning sea ice throughout much of its duration.

Gale force winds predicted for Beaufort, Chukchi and East Siberia Seas.

(Image source: Arctic Weather Maps)

The fact that this particular storm is forming in late summer is some cause for concern. The sea ice has been subjected to above freezing temperatures for some time. Melt ponds have increasingly formed over much of the Arctic and, since late June, most of the precipitation falling on the Arctic has been in the form of rain. The central ice pack is in complete chaos, with extensive thinning and fracturing surrounding a wide arc near the North Pole and a broad melt triangle full of broken ice and patches of open water extending far into the Laptev Sea. Further, the long duration of sunlight falling on the ice surface and penetrating into the ocean layer just beneath has likely warmed waters below the cold, fresh layer near the ice.

As the storm passes, its strong winds and cyclonic circulation have the potential to dredge up this warmer water and bring it in contact with the ice bottom. Such action can rapidly enhance melt, as we saw during the Great Arctic Cyclone of 2012. Since the brine channels are all mostly activated (with much ice in the region now above -5 degrees Celsius) Cyclonic pumping during storm events like this one can transport sea water directly through the ice to increase the size of melt ponds, to break, or to even disintegrate ice flows.

It is important to add the caveat that this particular storm in not predicted to be quite as long or as strong as the Great Arctic Cyclone of 2012 which, in its first week, coincided with a loss of 800,000 square kilometers of ice. But Arctic weather is nothing if not unpredictable and this particular event could just as easily fizzle as turn into an unprecedented monster.

That said, a number of concerning conditions have emerged just prior to this storm that may result in an enhanced effect on the ice. The first condition is that large sections of the Beaufort, East Siberian and Chukchi Seas are covered in thin, diffuse and mobile sea ice. These conditions are clearly visible in the surface shots provided by NASA/Lance-Modis:

In this section, as in other broad stretches of the Beaufort, the ice is reduced to a kind of slurry in which, as Neven over at the Arctic Ice Blog notes, the individual flows are completely degraded and difficult to make out. This slushy region is in direct contact with a region of mostly open water. Such areas of de-differentiated ice are likely to show greater mobility and enhanced wave action during storms, which puts them at risk of more rapid melt.

Another somewhat ominous note in advance of this storm is a rise in Arctic Ocean temperature anomalies over the past couple of days. NOAA’s surface temperature measure indicates a spreading pool of warmer than normal surface ocean conditions throughout the Arctic. In the region this storm is predicted to most greatly affect, the storm will have the potential to bring such warmer than normal surface waters into more consistent contact with the ice through the mechanical action of waves and by activating the brine channels in the ice. Further, a large pool of much warmer than normal surface water in the Chukchi Sea is likely to be driven deeper into the ice pack where it also may enhance melt.

(Image source: NOAA)

In general, there’s quite a bit of atmospheric and ocean heat energy for this storm to tap and fling about. Not only is the surface ocean warmer than 1971-2000 base temperatures, but most continental land masses surrounding the Arctic are showing highs between the mid 60s to upper 80s and lows between the 40s and upper 60s.

ECMWF model forecasts show the storm tapping some of this energy in advance of intensification, with a tongue of warm Alaskan and Canadian air being drawn into the storm at the 5,000 foot level late Monday and early Tuesday. Directly opposite, Siberia and Eastern Europe have hosted very warm air masses with daytime surface temperatures above the Arctic Circle reaching the upper 80s consistently over the past week. This warmth also encroaches just prior to storm intensification.

(Image source: ECMWF)

Added heat energy injected at the surface and at the upper levels will ensure that the vast majority of precipitation during this event emerges as rainfall.

Broader effects of this storm could be quite significant. The US Navy’s CICE models are showing a greatly enhanced ice motion throughout the duration of this storm as its counter-clockwise circulation is predicted to dramatically increase the movement of the Arctic’s remaining thick ice toward the Fram Strait. The Navy’s thickness monitor also shows a jump in ice thinning and dispersal throughout the ice pack over the duration of this event. In particular, the back end of remaining thick ice north of the Canadian Arctic Archipelago is mashed like a tube of tooth paste in the model run, pushing a broad head of ice toward the Fram. At the same time, a large section of Central ice, earlier thinned by PAC 2013, is projected to rapidly expand and further thin under the influence of this storm.

Note the rapidly expanding melt wave from the North Pole to the Laptev that appears in the final frames of the run below:

(Image source: US Navy)

So it appears we have a short duration but relatively high intensity Warm Storm event predicted to have broad-ranging effects from the Beaufort to the Central Arctic. An event that could have impacts similar to those of the Great Arctic Cyclone of 2012. Should such circumstances arise, it begs the question — is the Beaufort a region that is more likely to spawn these kinds of storms come late July through early to mid August? The region is now surrounded by increasingly warm continents. The observed weakening of the polar Jet Stream by 14% has resulted in a much greater transport of heat to the high continental boundary, as evidenced by a broad swath of heat-waves ringing the Arctic above the 60 degree North Latitude line. The increasingly thin Beaufort ice jutting out into this crescent of continental heat may well be the ignition point for major atmospheric instability, powerful storms and related heat transfer. Something to consider should these kinds of late season ice melters recur on a more frequent basis.

To this point, a new naming convention has been proposed over at the Arctic Sea Ice blog for summer storms that greatly impact the ice. Preliminary standards have been set for storms with a central pressure lower than 985 mb (at peak intensity) and a duration longer than 4 days. Suggestions for storm titles include traditional Inupiat names from this region or even the use of the names of prominent climate change deniers (My opinion is that both calling attention to major Arctic melt events and how climate change deniers have attempted to cover such events up would be an excellent use of such a convention, but I may be out-voted).

You can take part in the naming convention discussion on the Arctic Ice Blog by following this link here.

In conclusion, the potential arises for the first named Arctic Cyclone to result in dramatic melt and weakening of sea ice throughout the upcoming week. This potential heightens the risk for 2013 to be another record melt year and so we will continue monitoring the storm’s development closely for you.