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From Pole to Pole, Global Sea Ice Values are Plummeting
During
the record hot year of 2016, both Arctic and Antarctic sea ice
extents took a huge hit.
15
November, 2016
Extreme
warmth in the Arctic helped to produce leading losses there. Values
that began during January at 1 million square kilometers below
average have steadily declined as the months progressed to near 2
million square kilometers below average. Meanwhile, the Antarctic —
which began the year at near average sea ice extent values — saw
significant losses as the region grew anomalously warm during austral
spring. Today, sea ice extent values surrounding the Antarctic are
now also just shy of 2 million square kilometers below average.
(Zachary
Labe, one
of the most well-recognized up and coming U.S. climate scientists,
has produced this graph based on NSIDC recorded global, Arctic, and
Antarctic sea ice values. As you can see, global sea ice extent
during the hottest year on record has steadily plummeted to near 4
million square kilometers below average as the months progressed.
Image source: Zack
Labe’s Sea Ice Figures.
Data source: NSIDC.
You can also follow Zack’s
informative twitter feed here.)
In
total, global sea ice coverage is now about 3,865,000 square
kilometers below average.
If
you think that number sounds really big, it’s because it is. It
represents a region of lost ice nearly 40 percent the size of the
land and water area of the entire United States including Alaska and
Hawaii. To visualize it another way, imagine all of the land area of
Alaska, California, Texas, Montana, Arizona and New Mexico combined
and you begin to get the gist.
Sea
Ice Coverage — An Important, But Complex Climate Indicator
Many
climate specialists have viewed sea ice as a kind of climate change
canary in the coal mine.
Sea ice sits upon the warming oceans and beneath a warming
atmosphere. And these oceans are now
taking up the majority of the heat being trapped in the atmosphere by
fossil fuel emissions.
Warming ocean surfaces have a higher specific heat value than the air
and this greater
overall energy capacity in
warming regions generates a substantial blow to ice coverage even if
the initial water surface temperature swing is only moderate.
Once
sea ice is lost for a significant period, a kind of feedback loop
comes into play where dark ocean surfaces trap more of the sun’s
rays during polar summer than once-white ice coverage — which
previously reflected radiation back toward space. This newly absorbed
heat is
then re-radiated back into the local atmosphere during polar fall and
winter —
creating an inertial barrier to ice reformation and ultimately
generating a big jump in seasonal ocean and atmospheric surface
temperatures.
(Highly
pronounced ocean surface warming coupled with warm air invasions
appears to be generating the extreme losses to sea ice now seen in
the Arctic. The Barents Sea, shown above, has seen particularly
extreme warming. Note the 11 C above average hot spot near the sea
ice edge zone. In the Antarctic, the causes of losses remain
uncertain. However, atmospheric warming and shifts in the circumpolar
winds appear to be producing this effect even as slightly cooler than
average surface waters remain in place — possibly due to storm
related Southern Ocean upwelling and increasing fresh water outflows
from Antarctic glaciers. Image source: Earth
Nullschool.)
This
dynamic is particularly pronounced in the Arctic where a thawing
ocean surrounded by warming continents tends to readily collect heat
even as atmospheric energy transfers from the south, in
the form of warm wind events,
have grown more pronounced. An effect related to the climate change
influence known as Northern Hemisphere Polar Amplification.
In
the Antarctic, the stormy Southern Ocean generates up-welling. This
dynamic tends to cool the ocean surface even as it transfers heat
into the deeper ocean. And increasing stormy conditions surrounding
Antarctica related to climate change can intensify this effect. In
addition, warm
bottom waters melting sea-fronting glaciers in Antarctica produce a
lens of fresh water which cools the surface and also traps heat
below.
So the signal coming from Antarctica with regards to sea ice has
tended to be more mixed — with atmospheric warming and changes in
wind patterns generating more variable sea ice impacts relative to
the Arctic. So this year’s sea ice losses there are more difficult
to directly link to climate change even though climate change related
influences on the physical system in the Antarctic and among its
surrounding waters are becoming more and more apparent.
Zack
Labe notes
that:
The Arctic sea ice anomaly, however, fits with the ongoing Arctic amplification trend of thinning sea ice and loss of old ice. Additionally, it has been well noted in previous literature (i.e., http://onlinelibrary.wiley.com/doi/10.1029/2010GL044136/full …) concerning the increasing fall temperatures in the Arctic and possible causes.
Major
Volume Losses From 2015 to 2016
Despite
big losses to sea ice surrounding the Antarctic this fall, it is the
Arctic where the damage and risk of further loss is most pronounced.
Particularly, reductions to thicker, multi-year ice in the Arctic
during 2015 to 2016 have been exceptionally severe:
In
the above images, we see a comparison between late November sea ice
coverage and thickness as
provided by the U.S. Navy ARCc model.
The left frame represents late November of 2015 and the right frame
represents projected values for November 20, 2016. Note the greatly
reduced coverage in the 2016 image. But even more noteworthy is the
substantial loss of thicker ice in the Arctic Ocean north of the
Canadian Archipelago and Greenland.
These
two images tell a tale of a great loss of sea ice volume. One that
the sea ice monitor PIOMAS confirms.
According to PIOMAS, ice volume values during
October were tracking near lowest levels ever recorded.
And continued heat into November generates a concern that a period of
new record low volume levels may be on the way.
But
it’s not just the record low values that should be a concern. It’s
the location of the remaining thick ice that’s a worry as well. For
a substantial portion of the remaining thick ice is situated near the
Fram Strait. Wind and ocean currents tend to push ice out of the
Arctic Ocean and through the Fram. Ice tends to then be funneled down
along the coast of Greenland and on into the North Atlantic where it
melts. So the fact that a big chunk of the already greatly reduced
remaining thick ice now sits on the edge of the sea ice version of
Niagra Falls is not a good sign.
La
Nina Years Tend to Push More Heat Toward the Poles
It
is notoriously difficult to accurately forecast sea ice melt and
refreeze trends in the various seasonal measures for any given
individual year. And even many of the top sea ice experts have had a
devil of a time forecasting the behavior of sea ice during recent
years. However, one thing remains quite clear — the long term trend
for sea ice in the Arctic is one of rapid decline.
We
are now entering a situation where one very warm winter followed by
one warmer than normal summer could push Arctic sea ice values to
near the zero mark. A situation that could effectively set off a blue
ocean event in the near future. A number of prominent sea ice experts
have predicted that it’s likely that such a state will be achieved
rather soon — by
the early 2030s under current trends.
Others point
toward nearer-term loss potentials.
But there is practically no-one now saying, as was often stated
during the early 2010s, that a blue ocean event could hold off until
the early 2050s.
All
that said, the trajectory going into 2017 for the Arctic at present
doesn’t look very good. Both sea ice extent and volume are now at
or well below the previous low marks for this time of year. Remaining
thick ice positioned near the Fram Strait generates a physical
disadvantage to the ice in general. In addition, NOAA
has announced that La Nina conditions are now present in the
Equatorial Pacific.
And La Nina events tend to push more ocean and atmospheric heat
toward the poles — particularly toward the Arctic.
Links/Notes/Disclaimer:
Note:
This article is written as a follow-on to the previous blog post
— For
The Arctic Ocean Above 80 North, It’s Still Summer in November —
and they should be read together for context.
Disclaimer: I
asked PhD
student Zachary Labe to
make a general comment on sea ice trends, to which he generously
provided his particular take on the Arctic. I have also made my own
best-shot science and observation-based analysis of the situation
given current trends. Because of the fact that the present situation
is new and evolving, some of my statements may well pass outside the
bounds of currently accepted science. The fact that Labe commented in
this post does not, in this case, mean that he agrees fully or in
part with my particular initial rough analysis of the subject.
Hat
tip to Andy Lee Robinson
Hat
tip to Cate
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