Arctic Sea Ice Now Below 2014 in All Major Measures — Warm Storm Settles In
29
July, 2015
When
looking at Arctic sea ice melt, there are trends and there are
bounces. The great 1979 to 2015 melt we call a trend. The 2013 and
2014 rebound from all-time record lows during 2012? That we call a
bounce. But it’s starting to look more and more like the bounce is
ending and the long-term melt trend is starting to, inexorably,
reassert.
Overall,
it was a decent rebound. By September, minimum seasonal ice popped up
by about 3,500 cubic kilometers in the PIOMAS
volume record,
by about 1.4 million square kilometers in the Cryosphere
Today area measure,
and by 1.5 million square kilometers in the NSIDC
extent measure.
A decent rebound, but still about 11,000 cubic kilometers lower in
volume than 1979 (more than a 55 percent loss), about 1.9 million
square kilometers lower than 1979 in area (more than a 36 percent
loss), and about 1.9 million square kilometers lower than 1979 in
extent (about a 30 percent loss).
Sadly,
a bump of this kind does not a trend make. Looking at the overall
volume loss line (above), we can clearly see that the 2013 and 2014
rebound after 2012’s record low was plainly within the melt
progression’s boundaries. Moreover, out of the last 8 years, 2014
is the only year above base-line rate of loss at 3,200 cubic
kilometers per decade. A rate of loss that, if it continues would
bring us within striking distance of a dreaded ‘blue ocean’ type
event for the Arctic by the early 2020s.
Since
this trend is polar amplification driven — an underlying aspect of
phase 1 climate change forced by human greenhouse gas emissions —
the only major driver with the potential to challenge Arctic melt is
a large outflow of fresh water from Greenland. Such an outflow would
temporarily reduce ocean ventilation of heat through the sea surface
in the fresh water outflow region. The result being that surface
temperatures would, for a short time, cool in the outflow zone. This
would have an effect of regenerating sea ice in a larger
counter-melt-trend feedback. It’s likely that melt outflows from
Greenland would need to be significant enough to have profound
impacts on the Arctic environment as a whole. To hit anywhere near
these levels, we likely need to see in the range of at least a half
centimeter of sea level rise from Greenland melt alone each year. And
we are, as yet, nowhere near that rate of loss (although
we might get there in a decade or two or three).
So
though the recent 2012 Greenland melt high mark was likely enough to
push AMO negative, to
further weaken AMOC,
to develop a cool pool in the ocean south and east of Greenland, to
back a super hot Gulf Stream up to the US East Coast during the
winter of 2014-2015, and to set off a slew of nasty weather impacts
for the North Atlantic from 2012 through 2015, it was nowhere near
enough to upset the overall long-term, human heat-driven Arctic melt
trend. If such an event were to occur, what we would likely see is a
signature not only of a North Atlantic cool pool but also of more ice
in Baffin Bay, more ice in the North Atlantic itself and more ice on
the Arctic side near Greenland. A signal that we do not fully see at
this time.
It
is thus more likely that we will see a re-assertion of the overall
Arctic sea ice decline trend. And there are a growing number of
indicators that some of this re-assertion is starting to come about
during the summer of 2015.
All
Major Monitors Now Below 2014
For
the Summer of 2015, melt has been consistently strong — especially
for July. During most of the month, strong high pressure systems
dominated. This situation led to compaction, storm formation at the
sea ice edge, and a degree of sea ice export. It amplified solar
insolation at a time when the sun was near its seasonally highest
angle — enhancing surface melt and melt ponding.
As
of yesterday, the major extent monitors — JAXA and NSIDC — as
well as Cryosphere Today’s area monitor were all below or well
below the 2014 line. The ongoing and rapid July melt drove JAXA below
the 2014 line late last week while NSIDC hit below 2014 just
yesterday. As a result, NSIDC
sits at 7.2 million square kilometers extent or
7th lowest on record (a decline of 2 places since last week) and JAXA
shows a 6.79 million square kilometer extent or
5th lowest on record in the measure (also a decline of 2 place).
Cryosphere
Today’s area measure,
meanwhile, continued to drop — showing increasing divergence from
the 2014 line and hitting a 4th lowest area on record for the 27th (a
one place dip from last week).
(Sea
ice area dips to 4.67 million square kilometers or the fourth lowest
on record in the July 27th Cryosphere Today measure. Note the 2015
sea ice area trend line is indicated in yellow, the 2014 sea ice area
trend line in red. Image source: Cryosphere
Today.)
Overall,
these drop-offs are consistent with a returning to the long-term melt
trend in 2015. But it does not yet place 2015 in striking distance of
new all-time record end melt season lows set during 2012. And we’d
be quite surprised if it did. Larger ocean and atmospheric
teleconnections tend to drive increasing heat in the Arctic ocean
waters and airs and to increase sea ice transport to compound ice
weakness during El Nino year +1 and El Nino year +2. The most recent
record lows both occurred 2 years after El Nino (2007 and 2012).
Given the large ocean and atmospheric drivers related to this trend,
we may look to next year or, more possibly, 2017 as potential new
record low years.
Weather
Change on the Way
All
that said, it doesn’t mean that 2015 cannot surprise us or (2005,
an El Nino year, was also a record low year), at least, serve up some
interesting features. Notably, there’s a change in the weather on
the way.
Throughout
July, we saw what was, perhaps, the worst possible atmospheric regime
for sea ice melt during that month. Atmospheric heat was relatively
high, clear skies dominated allowing for enhanced surface melt
through direct solar heating, and the persistent high pressure
systems helped to drive compaction and export. Though the action of
gyres moving ice out of the Fram Strait was relatively moderate,
overall melt conditions were very strong.
In
particular, a synergy between the high pressure driven pole-ward pull
of sea ice away from the Siberian side of the Arctic and a
significant influx of warm water northward from the Pacific Ocean and
through the Bering and Chukchi Seas had a marked impact. You can see
the amazing melt progress led by these two influences in the
excellent animation provided by The
Great White Con below:
Now,
however, the high pressure is sliding increasingly to the Siberian
side of the Arctic. Meanwhile, a persistent storm is beginning to
take hold over the Beaufort Sea and Central Arctic. Overall, it’s
an increased storminess for the Arctic. One that is now driving 25-35
mph winds through the shattered ice sections of the Beaufort Sea.
There’s
some argument that storms are friendly to sea ice. And, perhaps, this
is more true during the June time-frame when storms can reduce
insolation and melt ponding. When they can spread the sea ice out to
increase overall albedo. But in the current melt regime, sea ice is,
overall, far more fragile. There is more latent heat in the Arctic
Ocean that is available for storm systems to tap in order to melt
ice. And it is this condition that is most at play as we enter late
July and early August.
(A
storm is predicted to persist over the Beaufort for at least the next
five days. Image source: Earth
Nullschool.)
Over
the next five days, the current storm is predicted to persist over
the Beaufort. It will rumble along, sending its 20-35 mph winds out
over the fractured multi-season ice and large stretches of open
water. It will linger, gobbling up little storms rushing north over
Alaska and the Bering. And it will lash the ice there with increasing
wave action, breaking the surface cool water cap and pumping warm
water up toward the ice from below.
In
addition, this Beaufort low will form a kind of dipole with a high
pressure system that will tend to remain on the Kara Sea side of the
Arctic Ocean. The net effect of the dual circulation of the high over
the Kara and the low over the Beaufort will be to lift the thick ice
away from its base of support along the Northern Canadian
Archipelago. The result is likely to be a continued widening of a
large polynya already developing there.
(Winds
cycling between a high pressure over the Kara and a storm over the
Beaufort may further widen a large polynya north of the Canadian
Archipelago over the next few days. Image source: LANCE
MODIS.)
Meanwhile,
milder compaction and sea ice retreat is likely to continue on the
Siberian side with ice recession particularly likely in the Kara,
Laptev, and East Siberian Sea regions.
Overall,
these factors should continue to drive melt enough to keep the
monitors at or below the 2014 line with particular risk of increased
divergence in the area measure over the coming week due to storm
activity in the Beaufort. There is an outside, though not entirely
negligible, risk that Beaufort storm activity will greatly impact the
already very fragile ice along the Chukchi Sea boundary toward the
Siberia side. Such an impact would result in still greater area and
extent impacts. But more likely is an enhanced winnowing of the
remaining multi-year ice together with a widening of the large
polynya north of the Canadian Archipelago.
Links:
Hat
tip to Humorta
(Please
support publicly funded, non special interest based science like the
fantastic work done by NSIDC, NASA, PIOMAS and JAXA which has made
this report possible)
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