For many months the weather pattern has been essentially fixed. A ridge over China and Eastern Russia combined with warm air flows over Central Asia to amplify heat from Siberia and on into the Arctic Ocean. On the other side of the Pacific, a harmonic pattern involving warm southerly air flows over Alaska and Western Canada has also transported an inordinate amount of highly anomalous heat into the Arctic.
These warm ridges have been consistently reinforced by high amplitude Jet Stream waves. During the Winter of 2013-2014, these same atmospheric heat transport engines collapsed the polar vortex, causing melt, avalanches, and 60 degree F temperatures for Alaska in January all while pulling Arctic air down over the Eastern United States throughout the winter months.
For Alaska, Western Canada and the Eastern US, it is a general pattern that has now lasted nearly 14 months. A blocking pattern that weather historians everywhere should take note of as a general evidence of atmospheric changes resulting from human-caused warming and a validation in observation to the findings of Dr. Jennifer Francis.
Early Season Melt in the Bering Sea
This warm air flow also severely retarded sea ice formation in the Bering Sea between Alaska and far Eastern Russia throughout winter. Now, this poorly formed ice is rapidly melting out as a barrage of storms and continued warm, southerly air flows result in ongoing degradation. Recent observations show a rather extreme loss of sea ice in this region over the past 18 days:
As we can clearly see in the two images above, both snow cover and sea ice have experienced severe losses in this region from April 10 to April 27. Warm southerly winds have continued to push ice northward enhancing melt as temperatures typically remained near or above -2 C (the temperature at which sea ice begins to melt) in most regions. Snow losses amplified warmer than freezing water flows into adjacent ocean basins, also enhancing sea ice losses as land masses continued to warm.
Heat Pulse for Bering, Chukchi, East Siberian and Beaufort Seas
Over the next six days, this general warming trend is expected to spike, bringing with it a front of much hotter than usual temperatures extending along a broad zone of the Arctic Ocean north of Canada, Alaska and East Siberia and nearly reaching the North Pole at maximum extent.
The pulse is expected to bring 18-32 F above average temperatures for this region, pushing daily highs into the mid 30s to mid 40s over the Arctic Ocean and to nearly 50 F over waters directly adjacent to the Alaskan coast. GFS model runs for May 2, 2014 show this powerful warm air invasion, indicated by the wave of green on the map below, extending well into the Arctic Ocean with extraordinarily warm temperatures in the mid-to-upper 60s over a broad swath of Central Alaska:
(GFS temperature model for May 2, 2014. Image source: University of Maine.)
Such an intense warm pulse will greatly involve the Bering, the Chukchi, the East Siberian and Beaufort Seas. It will likely most significantly impact sea ice in regions of the Bering Sea and near-shore zones of the Chukchi and Beaufort. The early season heat wave may also enhance the ice weakening process throughout the affected zone by softening the sea ice and by creating the potential for melt pond formation.
The Major Impact of Early Season Melt Pond Formation
During May and June, early melt pond formation can have a dramatic impact on sea ice melt much later in the season as the darker pools reduce ice sheet albedo serving as a kind of heat lens that bores down through the ice surface. Eventually, the melt ponds connect, forming larger and larger volumes over the ice face until the sea ice is almost completely overwhelmed. In the last phase, melt breaks down through the ice surface to contact the ocean. At this point, the sea ice is typically splintered into much smaller and disassociated fragments.
A recent paper in the journal Nature has found that a multiplication of such early season melt ponds may well be a predictive indicator of end season sea ice extent, area and volume values come September.
The paper notes:
Our simulations show that melt ponds start to form in May, a maximum extent of 18% is reached in the climatological mean at mid-July, and there are hardly any exposed ponds left by mid-August. The strong interannual variability and the positive trend are striking. Whereas in 1996, the year with the highest September ice extent since 1979, the maximum pond fraction reaches only 11%, in 2012, the year with the lowest September ice extent, up to 34% of the sea ice is covered by ponds.
(Major expanse of dark sea ice melt ponds in the Chukchi Sea during June of 2010. Image source: The Polaris Project.)
Achilles Heel For the Arctic During the Summer of 2014
The most recent hot pulse for this region may just be the first of many as the spring and summer melt season progresses. Jet Stream patterns continue to remain fixed, delivering much hotter than normal temperatures throughout the Western Canadian, Alaskan, and East Siberian regions. Furthermore, snow cover losses for these regions are particularly well advanced further enhancing the likelihood of warm air invasions from these rapidly heating continental zones. Anomalously large and extreme early season fires may also result in a degree of albedo loss as smoke and soot is drawn northward to darken both remaining snow cover and sea ice.
As such, this zone represents a kind of sea ice Achilles heel as the 2014 melt season progresses. If we do see major losses and a progression toward record melt, it will likely come as a result of extreme weather patterns emerging from the continental zones spanning East Siberia, Alaska and Western Canada.