ESA Says Northwest Passage Open

Satellites witness lowest Arctic ice coverage in history

14 September 2007

http://www.esa.int/esaCP/SEMYTC13J6F_index_0.html

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 ESA?s Envisat satellite, the dark gray colour 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.

Envisat ASAR mosaic of Arctic Sea

Mosaics of Arctic Ocean for 2005, 2006, 2007
"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.

ASAR image of the Northwest Passage

A 2007 ice-free portion of the Northwest Passage

The Polar Regions are very sensitive indicators of climate change. The UN?s
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-coloured
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
(IPY) - a large worldwide science programme 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.



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