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Summer 2014 Melt Season to Ramp up in Early May Heat Wave: Fixed Jet Stream, Dual Ridges Form Sea Ice Achilles Heel
30
April, 2013
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:
(LANCE-MODIS
comparison of Bering and Chukchi Sea Ice on April 10 [left image] and
April 27 [right image]. Image source: LANCE
MODIS. Hat
Tip to Arctic
Sea Ice Forums Poster Frivolousz21.)
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:
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.
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