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Delving Further into Uncharted Territory: Arctic Sea Ice Greatly Weakened at Start of Spring 2018
6
March, 2018
The
story of Arctic sea ice is one of short term complexity overlying an
inexorable long term trend of decline.
It has thus been difficult for sea ice monitors to forecast seasonal
ice growth and retreat, despite a larger and significant warming of
the Arctic.
(New
ice has formed north of Greenland following a massive polar warming
event last week. This ice is thin and faces the warm up of spring and
summer with uncertainty. Sitting over a region that is typically
filled with thick ice, it could provide a back-door for melt into the
Central Arctic come summer. As usual, weather will play a key role in
this year’s melt, despite the undeniable longer term trend of loss.
Image source: NASA.)
Undeterred by these
facts, a number of key factors stand out in 2018 — following a
winter in which the Arctic has suffered considerable warming and
related impacts to the ice.
Lowest
Sea Ice Extent; Warmest Freeze Season
Today, Arctic
sea ice extent is at its lowest levels on record.
Volume, is
at the second lowest levels ever measured.
And this year’s freeze season (October through February of
2017-2018) was the warmest ever recorded (see link below). Taken at
face value, these are pretty stark statistics. But they don’t tell
the whole story. Not by a long shot.
The
Arctic is warming up twice as fast as the rest of the world.
It has been doing so since around 2000 when Polar Amplification —
the science-based expectation that the poles will warm faster than
the globe as greenhouse gas levels rise — really began to kick in.
So the present warm peak in the Arctic is on top of a record spate of
accelerated warming. In the graphs it looks like a rocket ship taking
off.
Air temperatures (at 925 hPa) are a record high for the #Arctic freeze season (October - February, >67°N) in this data set
Graphic: http://sites.uci.edu/zlabe/arctic-temperatures/ …
We should be clear that
most of this warming has occurred during winter time. It’s warmth
that has softened the ice, thinned it. Produced a big push toward
thaw.
But like a cup of water with a single cube of melting ice in it
will resist surface temperatures above freezing, this thinning and
melting has yet to have have a significant impact on summer-time
temperatures in the high Arctic. That thinning skein of ice is still
doing its duty keeping the Arctic summer close to freezing. But it’s
a realistic question to ask — how much longer can it? What happens
when the majority of the summer ice is gone?
Such
radical warming has also had a number of environmental effects. It
is pushing fisheries that rely on cold water northward.
It is stressing key species like the Wright Whale, the Polar Bear,
and the Puffin. It is causing the permafrost to thaw, which produces
a number of environmental feedbacks. Not the least of which includes
land subsidence, the release of mercury into the Arctic environment
and global ocean, and the slow but rising expulsion of greenhouse
gasses long locked way.
Multiyear
Ice Has Pulled Away From Shore
The
thicker ice floes of yore are now mostly a bare memory. A
recollection of past cold blasted away by fossil fuel burning and
inexorable thaw. This year, an
LNG tanker crossed the thinning ice during winter time.
Bearing with it a great load of climate change quickening gas
destined to be burned in some nation still entangled by a
heat-producing web of gas plants, coal mines, and diesel and gasoline
cars.
According to the U.S. National Ice Center, this year’s ice (multi-year ice) has pulled completely away from the coast and the Northern Sea Route is dominated by first-year medium (0.7- to 1.2-meter) or first-year thick (1.2- to 2-meter) ice.
The
thick, multiyear
ice is
reduced to a phantom of its former girth and extent. It has drawn
back, pulling away from shore. Increasingly sequestered to more and
more remote regions. And on the run from the ocean swells, warmer
storms, and increasing instances of liquid rain that fall across an
Arctic that is facing violent transition.
Increasingly, it huddles
closer to Greenland and the Canadian Archipelago. But as we can see
in the image at the top of this post, even this region is no longer a
reliable sanctuary.
Cold
Pole Shift in Forecast — Canada/Alaska Predicted to See Abnormal
Warmth
As late winter
transitions into early spring, we enter the less certain time of melt
and thaw season. During recent years, as warming bloomed in the lower
latitudes, the Jet Stream which had slowed and meandered more during
winter due to polar warming, snapped back into place. This seasonal
flattening and speeding up of the upper level winds tended to harden
and deepen the cold pole at the north of our world. Reducing relative
temperature variance above normal averages even as melt season
advanced.
This created a kind of
Dr. Jekyll and Mr. Hyde relationship between winter and summer in
which high Arctic winter temps seemed outrageously warmer than normal
even as summer snapped back to more typical Arctic averages in the
furthest north locations.
(As
we enter spring and summer, high Arctic temperatures tend to regress
back toward the mean following winter warming. This is largely due to
the inertial cooling influence of ocean ice which will tend to keep
temperatures closer to the freezing line even as net energy gain is
ongoing. Loss of ice would result in the removal of this insulating
effect and likely push summer anomalies for the region into the +1 to
+5 C range. Image source: Zachary
Labe.
Data Source: DMI.)
But all is not well. The
loss of winter climate norms have done their damage. And the summers,
on balance, saw the edge ice retreat a bit further. Saw the
boundaries of Arctic cold pull a bit tighter and saw the open,
warmer, sunlight-capturing waters advance ever northward.
We don’t know if this
return to more normal temperatures for the high Arctic during summer
will save the ice from new record lows this year during melt season.
But we can track how thaw season is predicted to advance against a
greatly weakened Arctic sea ice pack. And this year, the cold pole
appears to be expected to shift over the land mass of western Siberia
during early March.
(A
warm North America, cool west Siberia dipole appears to be developing
during early March in the forecast models. If this trend reinforces,
it could leave large areas of ice open to early thaw from the Alaskan
and Canadian maritime to the Central Arctic. Note that residual
energy transfer along ocean zones remains in play in this forecast.
Image source: Climate
Reanalyzer.)
Meanwhile, on the North
American side, abnormal warmth is predicted to advance through
Alaska, Western Canada, and the Hudson Bay region.
If this trending location
of warm and cool extremes reinforces and holds through melt season
start, we can expect the front of melt advance to begin on the North
American side as the region near the Kara and Laptev seas resist melt
advance longer. Meanwhile, latent warmth over the Bering Sea and
Svalbard appear to be set to hold back late season refreeze in these
two key zones.
How this weather dynamic
plays out will determine if melt season 2018 begins on a record low
ramp and how resilient the ice will be to the seasonal thaw that is
on the way. We are presently in a situation where a record low start
is possible even as reasonable concerns about a potential rapid
summer melt progression are presently heightened.
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