Posts
I
have been debating Greg Braden on Facebook – mostly talking past
each other. We ended up discovering we were not QUITE as far apart
as we thought.
Climate
Trends in the Arctic as Observed from Space: It’s melting. Fast.
Greg
Braden
7
April, 2014
Earth’s
northern ice cap is heating up and melting down at an alarming, not
previously predicted, rate. A paper just out in Wiley
Interndisciplary Reviews: Climate Change, by Josefino Comiso and
Dorothy Hall looks at recent historic transformations in the Arctic
using satellite imagery, mainly from 1979 to the present. The decline
of Arctic ice is so extreme that ice thought to have existed for over
1450 years is melting now. (None of the sea ice is really ancient,
even the “old” ice recycles over geologically short time periods.
But in the near future there will be virtually no “old” ice left
in the region.)
According
to author Josefino Cosimo, of NASA, “The Arctic region has been
warming faster than anywhere else in the globe from 1981 to 2012.
Such warming is manifested strongly in all components of the
cryosphere in the Northern Hemisphere.”
The
following list of chilling, or rather, not chilling, facts is
paraphrased from the paper:
The
following list of chilling, or rather, not chilling, facts is
paraphrased from the paper: Warming
in the region has been amplified … with the rate of warming
observed to be ~0.60±0.07 o
C per decade in the Arctic (>64
oN) compared to ~0.2 o C per decade globally during the last three
decades.
- sea ice extent has been declining at the rate of ~3.8% per decade,
- while the perennial ice (represented by summer ice minimum) is declining at a much greater rate of ~11.5% per decade.
- Spring snow cover [is] declining by –2.12 % per decade for the period 1967 to 2012.
- The Greenland ice sheet has been losing mass at the rate of ~123 Gt per year (sea level equivalence of 0.34 mm per year) during the period from 1993 to 2010
- for the period 2005 to 2010, a higher rate of [Greenland ice sheet] mass loss of ~228 Gt per year has been observed.
- the average area of mountain glaciers has declined by as much as 10% per decade during the period from 1960 to 2000.
- Increases in permafrost temperature have also been measured in many parts of the Northern Hemisphere while a thickening of the active layer that overlies permafrost and a thinning of seasonally-frozen ground has also been reported.
Here
is the movie version of this review paper
The
review looks at clouds, albedo, and the Arctic Oscillation for
insight as to how this is all happening. The Arctic Oscillation is
one of those medium-term climate variations (like ENSO) which
involves a large scale shift in the movement of air masses from one
perennial pattern to another, often accompanied by effects having to
do with sea surface temperatures or sea currents.
The
Arctic Oscillation (AO), often referred to as Northern Annular Mode
(NAM), has been regarded as among the most dominant modes in the
[Northern Hemisphere], affecting atmospheric circulation and climate
in the Arctic. Its direct impacts on the sea ice cover and wind
circulation patterns have been evaluated using AO indices as
presented for the entire year on a monthly basis in Figure 9a and for
the winter period in Figure 9b. The plots show that the indices for
both monthly and for the winter season are mainly positive since 1988
although there are years (e.g., 2010) when they become strongly
negative. It has been previously reported that negative AO indices
are associated with extensive ice cover while positive indices would
correspond to a reduced sea ice cover. However, the indices have
become nearly neutral in the recent decade while the sea ice cover
continued to decline.
The authors conclude that the link between the Arctic Oscillation and recent changes in the Arctic is unclear. This is hard to interpret without further research but it may be bad news: The recent changes seen in the Arctic and possibly effects not covered in this paper (but discussed frequently on this blog) on global weather don’t seem to be associated with “natural variation.”
The
graphic at the top of the post is figure one from the paper, and has
this caption: Location Map of the Arctic Region including average sea
ice extent (yellow line), sea ice cover during record minimum in
summer of 2012 (shades of white), continuous and discontinuous
permafrost (shades of pink), glacier locations (gold dots) and snow
cover (average location of 50% snow line in black and maximum snow
line in green as inferred from MODIS data).
noth,,,ng new
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