Posts
Ten Mile Wide Chunks of Arctic Sea Ice are Disintegrating North of Svalbard
14
June, 2016
Over
the past 10 days, the rate of sea ice extent loss in the Arctic has
slowed down somewhat.
And as a result sea ice extent measures, though maintaining in record
low ranges, are much closer now to the 2012 line. Low pressure
systems have come to dominate the Arctic Ocean zone. And the
outwardly expanding counter-clockwise winds from these systems have
tended to cause the ice to spread out and to thin. In the past, such
events were seen as an ice preserving feature. But this year, there’s
cause for a little doubt.
The
first cause comes in the form of record Arctic temperatures for all
of 2016. As
Zack Labe shows in the compelling graphic below,
not only has the first half of 2016 been a record warm six months for
the Arctic, it’s been a record warm half-year like no other.
(The
first half of 2016 is about 1.5 C hotter in the Arctic than the
previous record hot year. It’s a huge jump to new record warmth
that should cause pretty much everyone to feel a deep sense of
concern about this sensitive region. Image source: Zack
Labe.)
And
if extra heat is guaranteed to do one thing — it’s melt frozen
water. We can see that in the current near
record low snow coverages for
the Northern Hemisphere. We can see it in the fact that — despite
what would be ‘bad melt’ weather conditions such as cloud cover
and low pressure systems dominating the Arctic during the middle of
June — Arctic
sea ice extents are still in record low ranges and
Arctic sea ice volume continues
to track just below 2012’s record low trajectory.
And we can certainly see it in the fact that despite the clouds that
would normally promote cooler Arctic conditions during this time of
year, surface
temperatures have remained well above normal for the majority of
June.
Overall,
these conditions are unprecedented for the Arctic. And, in microcosm,
we can tell a little bit of this story of heat by tracking the life
of a ten mile wide hunk of ice that was recently blown away from the
ice pack and into the warming waters north of Svalbard.
Ocean
Zone North of Svalbard — A New Sea Ice Melt Field
On
June 8th, this ten-mile wide chunk of ice was ushered away from a
thinning but concentrated grouping of ice about 80 miles to the North
of the Island Archipelago of Svalbard. In past decades during June,
the sea ice had tended to remain closer to Svalbard, often enveloping
this Arctic island chain straddling the 80th parallel. But during
recent years sea surfaces around Svalbard have dramatically warmed
due to a human-forced heating of the atmosphere and oceans. And
today, sea surface temperatures surrounding Svalbard range from
1 to 8 degrees Celsius above 20th Century averages.
That’s
still cold water in the range of 32 to 46 F. At least to the human
perspective — as neither you nor I would find it a pleasant
experience to plunge into sea waters that are still relatively close
to freezing. But to sea ice, this water is basically warm enough to
represent an oceanic killing field.
By
June 10, our ten mile wide hunk of ice had been ejected about 30
miles into this warm water zone north of Svalbard. After only two
days, the previously contiguous structure of the ice is riddled with
cracks large enough
to be plainly visible in the 250 meter satellite resolution.
The sudden contact with warmer waters was more than enough to shatter
the surface of this island-sized hunk of Arctic sea ice.
Export
into warmer waters has long been a melt issue for ice moving out
through the Fram Strait. And loss of ice in this fashion due to
strong winds circulating clockwise around Greenland has become a
growing concern. Ice originating in the thick (though much thinner
than in past decades) ice pack north of Greenland can be funneled
along the Greenland Coast and eventually propelled out into the
warmer waters of the North Atlantic where it has no chance to
survive.
But
this is exactly what happened to this 10 mile wide chunk of ice as it
entered waters North of Svalbard. It exited the ice pack, lost access
to the fresh water field protecting the ice. It entered 1-3 C surface
waters. And it basically disintegrated.
Arctic
Ocean Near Summer Melt Tipping Points?
Added
Arctic heat is not just a measure, therefore, of atmospheric
temperatures. It’s a measure of implied ocean surface heat and
ocean heat lurking just beneath the surface. In the end, what we see
is that new ways to lose sea ice are now emerging. And it appears
that sea ice export into the northern Barents and near Svalbard
waters is yet one more sea ice melt risk potential. It’s a matter
worth bringing up due to the simple fact that this zone of ocean
water was once frozen, was once a consistent part of the Northern
Hemisphere ice pack. And after warming just enough, it’s a region
that is now hostile to sea ice.
(More
reliable US Navy ARCc model shows rapid thinning of remaining
Beaufort sea ice taking hold over the next seven days. With so much
heat baked into the Arctic over the past six months, we should remain
vigilant regarding outlier melt possibilities for 2016. Image
source: US
Navy.)
Looking
north, there’s risk that human caused climate change will drive
that ice hostility zone into the near polar region itself. During the
melt phase, broken ice can generate a bit of negative feedback by
promoting cloud formation through increased water evaporation and
reduced albedo as surface melt ponds are essentially dumped back into
the ocean. But such floes are at the mercy of transport and waves.
And they sit upon a warming surface ocean. A discontinuous floe can
hit a melt tipping point pretty rapidly — covering a large region
and then disappearing in a very short period. We’ve seen instances
of such events during late June for Baffin Bay, Hudson Bay, and the
Kara Sea.
Now,
much of the Arctic Ocean is covered by these floes. And with so much
heat in the system, it’s worth considering that the old rules no
longer fully apply. It’s worth realize that the ice is dancing in
an increasingly tenuous temperature zone between the warming waters
below and the warming airs above.
Links:
Hat
tip to Neven
No comments:
Post a Comment
Note: only a member of this blog may post a comment.