It appears that conditions
have conspired to generate maximal areal coverage but observe that half the
area and the most northerly half even is running thin opening the door for a
real clean out next year. There is yet
little if any evidence that we have seen a change in delta H that has dominated
since the late seventies.
Thus this looks
at best to be a fortuitous anomaly not unlike the year 2007 which is six years
ago.
Thus next year
does bear watching particularly if we have evidence of real accumulation to
counter the trend line. The right
combination of winds though could show a sharp drop and records again broken
simply because the ice pack is not getting stronger. We are dealing with a powerful decadal trend
linked strongly to the ongoing maxima in the South Atlantic that is a long ways
from been over or even precipitously reversed which is now how I expect this
ultimately to end.
Arctic Ice Almost Back
To 2002 Levels
Posted
on September 2, 2013by stevengoddard
One
of alarmist’s favorite games is saying that we aren’t allowed to look at Arctic
ice until September. So it is now safe to look.
This
year has obliterated the record for year over year ice gain, by a factor of
two. It is now close to what it was in 2002
Arctic
sea ice extent maintained a steady, near-average pace of retreat through the
first half of August, making it highly unlikely that a new record low minimum
will be reached this year. Nevertheless, there are extensive areas of low
concentration ice, even in regions close to the North Pole, atmospheric
pressure and temperature patterns this summer have differed markedly from those
experienced in 2012; cooler than average conditions have prevailed over much of
the Arctic Ocean. By contrast, Antarctic sea ice is near a record maximum
extent for mid-August.
Overview
of conditions
Sea
ice retreat through the first half of August was near average, bringing the ice
extent to 5.94 million square kilometers (2.30 million square miles). Sea ice
extent continues to track well below average levels (average of 1981 to 2010),
though remains within two standard deviations of the long-term mean. Retreat
rates increased slightly in the western Beaufort Sea and Chukchi Sea, but ice
cover remains extensive in those regions compared to 2012. Another major
difference between ice extent during 2012 and this year is the much greater
extent in the East Siberian Sea. Low ice extent in this region observed last
year was in part attributed to the effects of the “Great Cyclone of 2012” (see
previous post of August
14, 2012). On the eastern side of the Arctic near Europe and Greenland, the
extent remains below average.
Conditions
in context
The
sea ice retreat rate averaged from August 1 to 18 was near average at
approximately 75,000 square kilometers (29,000 square miles) per day. However,
satellite data show extensive low-concentration areas within the ice cover,
which appear to have developed in response to the frequent passage of storm
systems. These weather patterns also result in lower-than-average air
temperatures over the Arctic. Temperatures in the central Arctic at the 925 hPa
level have been 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below
average since late July.
A
bit thin on top
Satellite
data from the AMSR-2 instrument and MODIS show an unusually large expanse of
low-concentration sea ice (20 to 80% cover) within our extent outline (15% or
greater, using the SSM/I sensor) spanning much of the Russian side of the
Arctic and extending to within a few degrees of the North Pole. A small area
north of the Kara Sea has concentrations below 30%. This is likely in part a
result of the dispersive effect of low-pressure systems that have migrated
across the central Arctic over the past month. While some of the low
concentrations recorded by AMSR-2 may be due to surface melt on sea ice, the
MODIS image confirms that a large region is covered by isolated floes. The
tendency towards a more open pack, with large areas of open water between ice
floes, has increased in the past decade as the ice cover has thinned, as well
as a tendency for formation of large polynyas (see ASINA posts for September 2006) and areas
of pack detached from the main Arctic ice cover (such as mid-August
2012). The University of Washington’s Pan-Arctic
Ice Ocean Modeling and Assimilation System (PIOMAS) model and other
models of ice thickness continue to indicate thin ice cover this summer.
A
comparison of average temperature and sea level pressure maps for June and July
of 2012 (left diagrams) and 2013 (right diagrams) help us to understand why ice
extent is higher in 2013. The pattern of unusually low pressure centered near
the pole in 2013 has helped to spread the ice out and is consistent with
generally cool conditions over much of the Arctic Ocean, inhibiting melt. By
contrast, in the summer of 2012, a broad region of unusually high pressure
centered over Greenland, in combination with below average pressure centered
over the East Siberian and Chukchi seas, led to winds over the Beaufort Sea
with a more southerly component than is usually the case, leading to warm
conditions. That high pressure last year over Greenland also contributed to a
record melt season for the Greenland ice sheet. Melt this year over the ice
sheet has been more moderate, though still above rates seen in the 1990s. See
our upcoming Greenland Today site post later this week.
Can’t
get there from here
Projections
of the likely minimum extent this year based on retreat rates from past years
argue that it is highly unlikely that sea ice will surpass the record-setting
low extent seen in 2012. With retreat rates similar to those of 2007 to 2012,
the minimum extent would be near 5.0 million square kilometers (2.0 million
square miles) in mid-September.
Record
extent in the Antarctic
Antarctic
sea ice extent for August 19 is 18.70 million square kilometers (7.22 million
square miles), a record or near-record high level (August 19, 2010 was
similarly high), led by unusually extensive ice in the Bellingshausen,
Amundsen, and Ross seas, and in the western Indian Ocean sector. Climate
conditions since June have been variable, but the most recent surge in ice
growth has occurred during a period of unusually high pressure over the center
of the continent, resulting in a slowing of the circumpolar winds, warm winter
conditions for the central ice sheet areas (Vostok Station and Amundsen-Scott
South Pole Station both had periods of spring-like -30s earlier in the month),
and cold conditions in the Bellingshausen, allowing ice to grow extensively
there.
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