Sept.
14, 2007
SATELLITES
WITNESS LOWEST ARCTIC ICE COVERAGE IN HISTORY
The area covered by sea ice in the
Arctic has shrunk to
its lowest level this week since satellite measurements began nearly 30
years
ago, opening up the Northwest Passage – a long-sought short
cut between Europe
and Asia that has been historically impassable.
In the mosaic image above, created
from nearly 200 images
acquired in early September 2007 by the Advanced Synthetic Aperture
Radar
(ASAR) instrument aboard the European Space Agency's (ESA) Envisat
satellite,
the dark gray color represents the ice-free areas while green
represents areas
with sea ice.
Leif Toudal Pedersen from the Danish National Space Centre
said: "We
have seen the ice-covered area drop to just around 3 million sq km
which is
about 1 million sq km less than the previous minima of 2005 and 2006.
There has
been a reduction of the ice cover over the last 10 years of about 100
000 sq km
per year on average, so a drop of 1 million sq km in just one year is
extreme.
"The strong reduction in just one
year certainly
raises flags that the ice (in summer) may disappear much sooner than
expected
and that we urgently need to understand better the processes involved."
Arctic sea ice naturally extends its surface coverage each
northern winter
and recedes each northern summer, but the rate of overall loss since
1978 when
satellite records began has accelerated.
The most direct route of the Northwest Passage (highlighted in
the top
mosaic by an orange line) across northern Canada
is shown fully navigable, while the Northeast
Passage
(blue line) along the Siberian coast remains only partially blocked. To
date,
the Northwest Passage
has been predicted to
remain closed even during reduced ice cover by multi-year ice pack
– sea ice
that survives one or more summers. However, according to Pedersen, this
year’s
extreme event has shown the passage may well open sooner than expected.
The previous record low was in 2005 when the Arctic area
covered by sea ice
was just 4 million sq km. Even then, the most direct Northwest Passage did not fully
open.
The Polar
Regions are
very sensitive indicators of climate change. The United Nations'
Intergovernmental Panel on Climate Change showed these regions are
highly
vulnerable to rising temperatures and predicted the Arctic
would be virtually ice free by the summer of 2070. Still other
scientists
predict it could become ice free as early as 2040 due to rising
temperatures
and sea ice decline.
Because
sea ice has a bright surface, the majority of solar energy that hits
it is reflected back into space. When sea ice melts, the dark-colored
ocean
surface is exposed. Solar energy is then absorbed rather than
reflected, so the
oceans get warmer and temperatures rise, making it difficult for new
ice to
form.
The Arctic
is one of
Earth’s most inaccessible areas, so obtaining measurements of
sea ice was
difficult before the advent of satellites. For more than 20 years, ESA
has been
providing satellite data to the cryosphere communities. Currently, ESA
is
contributing to the International Polar Year – a large
worldwide science
program focused on the Arctic
and Antarctic.
Since 2006, ESA has supported Polar View, a satellite
remote-sensing
programme funded through the Earthwatch GMES Service Element (GSE) that
focuses
on the Arctic and
the Antarctic.
In 2009, ESA will make another significant contribution to cryosphere
research
with the launch of CryoSat-2. The observations made over the three-year
lifetime of the mission will provide conclusive evidence on the rates
at which
ice cover is diminishing.
##
Contact:
Mariangela D'Acunto
European
Space Agency
39-069-418-0856
mariangela.dacunto@esa.int
This
text derived from:
http://www.esa.int/esaEO/SEMYTC13J6F_planet_0.html
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