The sea ice appears to be holding up this year so far. It could
leave us with a modest level of recovery. We also know though, that
the right wind combination can turn that on its head, so while losses
matching last year appear improbable, they are not impossible. In the
meantime, I have no good reason to think that the positive delta heat
from the gulf stream has abated yet. That would likely express
itself best with a reversal in the Antarctic which is still appears
to be maxing out.
So far, no dramatics this year, but the North West Passage should be
open in late August.
At the same time, I suspect that the gross ice content is also
continuing its decline and generally getting thinner.
Current State of
the Sea Ice Cover
J. C. Comiso, C. L.
Parkinson, T. Markus, D. J. Cavalieri and R. Gersten
The sea ice cover is
one of the key components of the climate system. It has been a
focus of attention in recent years, largely because of a strong
decrease in the Arctic sea ice cover and modeling results that
indicate that global warming could be amplified in the region by a
factor of about 3 to 5 times on account of ice-albedo feedback. This
results from the high reflectivity (albedo) of the sea ice compared
to ice-free waters. A satellite-based data record starting in late
1978 shows that indeed rapid changes have been occurring in the
Arctic, where the perennial ice cover has been declining at the rate
of about 13% per decade and the ice cover as a whole has been
declining at the lesser rate of about 5% per decade. In the
Antarctic, the trend is opposite to that in the Arctic, with the
sea ice cover increasing at about 1 to 2 % per decade. This is
despite unusual warming in the Antarctic Peninsula region and
declines in the sea ice cover in the Amundsen/Bellingshausen Seas of
about 6% per decade. In the Arctic, a slight recovery in the sea
ice cover has been observed in 2008 and 2009, following a major
decline of the ice in 2007, while in the Antarctic, the sea ice cover
was more extensive than normal in 2007, 2008, and 2009. Shown
below are up-to-date satellite observations of the sea ice covers of
both the Arctic and the Antarctic, along with comparisons with the
historical satellite record of more than 30 years. The plots and
color coded maps are chosen to provide information about the current
state of the sea ice cover and how the most current daily data
available compare with the record lows and record highs for the same
date during the satellite era..
Figure 1: 10-year
averages between 1979 and 2008 and yearly averages for 2007, 2012 and
2013 of the daily (a) ice extent and (b) ice area in the Northern
Hemisphere and a listing of the extent and area of the current,
historical mean, minimum, and maximum values in km2.
Figure 2: Color-coded
map of the daily sea ice concentration in the Northern Hemisphere for
the indicated recent date along with the contours of the 15% edge
during the years with the least extent of ice (in red) and the
greatest extent of ice (in yellow) during the period from November
1978 to the present. The extents in km2 for the current and for
the years of minimum and maximum extents are provided below the
image. The different shades of gray over land indicate the land
elevation with the lightest gray being the highest elevation.
Figure 3: 10-year
averages between 1979 and 2008 and yearly averages for 2007, 2012 and
2013 of the daily (a) ice extent and (b) ice area in the Southern
Hemisphere and a listing of the extent and area of the current,
historical mean, minimum, and maximum values in km2.
Figure 4:Color-coded
map of the daily sea ice concentration in the Southern Hemisphere for
the indicated recent date along with the contours of the 15% edge
during the years with the least extent of ice (in red) and the
greatest extent of ice (in yellow) during the period from November
1978 to the present. The extents in km2 for the current and for
the years of minimum and maximum extents are provided below the
image. The different shades of gray over land indicate the land
elevation with the lightest gray being the highest elevation.
Figure 5. Seasonal
cycle of Northern Hemisphere sea ice extents (a) and areas (b), given
as daily averages, for the years 2006 through 2013. The vertical line
represents the last data point plotted.
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