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Big Warm-up Predicted for Northwest Territory as Pacific Side of Arctic Melts Out Early
17
April, 2014
The
long-term trend for Arctic sea ice is inexorably down.
Year-after-year, decade-after-decade, the human-driven accumulation
of heat in the Arctic has taken a terrible toll. Recently, mid
March through mid April showed record low sea ice extents for any
period since record keeping began in 1979.
Over
the past two weeks, extent levels bounced back to around 4th to 6th
lowest on record as winds shifted to north-to-south through the broad
region between Greenland and the Kara Sea. For this region, melt
pressure had been quite strong throughout Winter as a powerful warm
flow of air flooded up from the North Atlantic.
(Ice
in the Bering and the Sea of Okhotsk is rapidly melting. Warming and
sea ice melt ramp-up may also be on tap for both the Hudson Bay and
the Beaufort as south-to-north air flows associated with the
Ridiculously Resilient Ridge intensify. Image source: NSIDC.)
The
shift, which has occurred coincident with upper-level winds running
up from the Ridiculously Resilient Ridge in the Eastern Pacific, over
Alaska and the Northwest Territories of Canada, into the Beaufort and
on past the pole, has been pushing sea ice southward toward the
Barents and into the Fram
Strait.
The result has been minor sea ice expansion in the near Greenland
region at the cost of much more rapid melt in the Bering Sea, the Sea
of Okhotsk and a very earl season break up of ice in the Beaufort.
Pacific
Side Warming and Beaufort Break-up
Overall,
this Pacific-side warming of the Arctic has driven extent levels back
down into the range of 3rd to 4th lowest on record for this time of
year. And rapid melt in the Bering, the Sea of Okhotsk, together with
warming in the Beaufort and Hudson Bay may result in new challenges
to record lows over the coming days.
By
late April, break-up of Beaufort Sea ice is particularly dramatic
with very large polynyas forming in a broad region into and north of
the Canadian Archipelago and extending on into the off-shore region
of the Mackenzie Delta:
(The
Beaufort Sea shows extensive break-up and lackadaisical re-freeze on
April 26th 2015. Note the extensive dark cracks and polynyas [holes]
in the MODIS satellite image above. Such late-spring proliferation of
polynyas and cracks can critically reduce albedo as melt season
progresses. The Beaufort’s location also makes it vulnerable to
continued warm air influx over a very warm Northeastern Pacific
Ocean. Image source: LANCE
MODIS.)
Temperatures
within the Beaufort Sea and near the Canadian Archipelago are still
cold enough to support some re-freeze in the Polynya regions.
However, closer to the Mackenzie Delta, temps have trended more and
more toward near freezing or above freezing levels (sea water freezes
at around 28 degrees Fahrenheit). The result is a rather large region
with no new ice formation.
More
Warm air on the Way
As
of 5 PM Eastern Standard time, temperatures in the Mackenzie Delta on
the shores of the Beaufort Sea were pushing 32 degrees Fahrenheit.
Meanwhile, 50 degree temperatures dominated the region of Great Slave
Lake further upstream and southward. These readings are in the range
of 8-15 degrees above normal for this time of year, resulting in an
early melt pressure for the Mackenzie River and for coastal regions
near the post-thaw river outflow zones.
(Big
warm-up near the Mackenzie River and through the Northwest Territory
in April 28th’s GFS model prediction. Temperatures in the low
70s gather around Great Slave Lake as above freezing temperatures
drift down the Mackenzie River reaching all the way to Arctic Ocean
Shores. Note near and above sea water freezing temperatures [28 F]
throughout the Bering, Beaufort, northwest sections of the Canadian
Archipelago and Hudson Bay in the above image. Image source: Earth
Nullschool.)
This
warm pool is predicted to intensify through tomorrow with
temperatures reaching the low 70s Fahrenheit (22 C) near Great Slave
Lake and temperatures along Mackenzie Delta shores continuing to edge
up over freezing. The warm pool will then linger for another few days
before shifting east over Hudson Bay through early next week, pushing
temperatures between 10 to 25 degrees Fahrenheit above normal there.
By
late next week, long
range forecasts show
another warm ridge extension through the Mackenzie Delta and melt
pressure on the near-shore Beaufort re-intensifying.
Overall,
with Arctic Oscillation predicted to remain neutral, melt pressure in
the Arctic would tend to reduce somewhat. However, with both Bering
and Okhotsk rapidly melting out and with warmth predicted to persist
and intensify for those seas as well as for the Beaufort and for
Hudson Bay, it appears there’s an even shot that early melt season
will proceed at a more brisk than typical pace — again challenging
new record lows into early May.
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