———————————————————–
I didn’t expect to see things happen this quickly.
The ice shelf is hanging by a thread – we’ll know
in the next few days or weeks what its fate will be.”
———————————————————–
EurekAlert! — AAAS
Public release date: 25-Mar-2008
British Antarctic Survey
Contact: Athena Dinar
a.dinar@bas.ac.uk
44-122-322-1414
Antarctic Ice Shelf ‘Hangs By a Thread’
British Antarctic Survey has captured dramatic
satellite and video images of an Antarctic ice
shelf that looks set to be the latest to break
out from the Antarctic Peninsula. A large part of
the Wilkins Ice Shelf on the Antarctic Peninsula
is now supported only by a thin strip of ice
hanging between two islands. It is another
identifiable impact of climate change on the
Antarctic environment.
Scientists monitoring satellite images of the
Wilkins Ice Shelf spotted that a huge (41 by 2.5
km) km2 berg the size of the Isle of Man appears
to have broken away in recent days – it is still
on the move.
Glaciologist Ted Scambos from the University of
Colorado alerted colleagues Professor David
Vaughan and Andrew Fleming of the British
Antarctic Survey (BAS) that the ice shelf looked
at risk. After checking daily satellite pictures,
BAS sent a Twin Otter aircraft on a
reconnaissance mission to check out the extent of
the breakout.
Professor Vaughan, who in 1993 predicted that the
northern part of Wilkins Ice Shelf was likely to
be lost within 30 years if climate warming on the
Peninsula were to continue at the same rate, says,
“Wilkins is the largest ice shelf on the
Antarctic Peninsula yet to be threatened. I
didn’t expect to see things happen this quickly.
The ice shelf is hanging by a thread – we’ll know
in the next few days or weeks what its fate will
be.”
Jim Elliott was onboard the BAS Twin Otter to
capture video of the breakout for Vaughan and
colleagues. He says,
“I’ve never seen anything like this before – it
was awesome. We flew along the main crack and
observed the sheer scale of movement from the
breakage. Big hefty chunks of ice, the size of
small houses, look as though they’ve been thrown
around like rubble – it’s like an explosion.”
The breakout is the latest drama in a region of
Antarctica that has experienced unprecedented
warming over the last 50 years. Several ice
shelves have retreated in the past 30 years – six
of them collapsing completely (Prince Gustav
Channel, Larsen Inlet, Larsen A, Larsen B,
Wordie, Muller and the Jones Ice Shelf.)
Professor Vaughan continues, “Climate warming in
the Antarctic Peninsula has pushed the limit of
viability for ice shelves further south – setting
some of them that used to be stable on a course
of retreat and eventual loss. The Wilkins
breakout won’t have any effect on sea-level
because it is floating already, but it is another
indication of the impact that climate change is
having on the region.” Ted Scambos of the
University of Colorado says,
“We believe the Wilkins has been in place for at
least a few hundred years. But warm air and
exposure to ocean waves are causing a break-up.”
###
Issued by British Antarctic Survey Press Office.
Athena Dinar, tel: +44 (0)1223 221414; mob: 07740
822229; email: a.dinar@bas.ac.uk
Science contact: Professor David Vaughan, British
Antarctic Survey, +44 (0)1223 221643; email:
dgv@bas.ac.uk
Press contact at NSIDC, Stephanie Renfrow:
srenfrow@nsidc.org or +1 303 492-1497
Notes for editors
Pictures (stills and video) and location maps are
available from the BAS Press Office as above. The
Wilkins Ice Shelf covered an area of 16,000km2
(the size of Northern Ireland). Having been
stable for most of the last century it began
retreating in the 1990s. A major breakout
occurred in 1998 when 1000km2 of ice was lost in
a few months.
Satellite images processed at the US National
Snow and Ice Data Center revealed that the
retreat began on February 28 when a large (41 by
2.5 km) iceberg calved away from the ice shelf’s
south-western front. In a series of images, the
edge of the shelf proceeded to crumble and
disintegrate in a pattern that has become
characteristic of climate-caused ice shelf
retreats throughout the northern Peninsula,
leaving a sky-blue patch spreading across the
ocean surface compose of hundreds of large blocks
of exposed old glacier ice (see pictures). By 8
March, the ice shelf had lost just over 570 km2,
and the patch of disintegrated Antarctic ice had
spread over 1400km2. As of mid-March, only a
narrow strip of shelf ice was protecting several
thousand kilometres of potential further break-up.
The recent break out leaves a thin strip of ice
between Charcot and Latady islands on the
Antarctic Peninsula.
Climate warming has increased the volume of
summer meltwater on glaciers, which has weakened
ice shelves. Sea ice, which protects ice shelves
from ocean swell, has reduced also as a result of
warming temperatures.
The collapse of the 3250 km2 Larsen B Ice Shelf
took place in 2002. During the past 40 years the
average summer temperatures in this region of the
north-east Peninsula has been 2.2°C. The western
Antarctic Peninsula has showed the biggest
increase in temperatures (primarily in winter)
observed anywhere on Earth over the past
half-century.
The Antarctic Peninsula is an area of rapid
climate change and has warmed faster than
anywhere else in the Southern Hemisphere over the
past half century. Climate records from the west
coast of the Antarctic Peninsula show that
temperatures in this region have risen by nearly
3°C during the last 50 years – several times the
global average and only matched in Alaska.
Ice sheet – is the huge mass of ice, up to 4 km
thick, that covers Antarctica’s bedrock. It flows
from the centre of the continent towards the
coast where it feeds ice shelves.
Ice shelf – is the floating extension of the
grounded ice sheet. It is composed of freshwater
ice that originally fell as snow, either in situ
or inland and brought to the ice shelf by
glaciers. As they are already floating any
disintegration (like Larsen B) will have no
impact on sea level. Sea level will rise only if
the ice held back by the ice shelf flows more
quickly into the sea.
Regular satellite images of Wilkins Ice Shelf
were obtained using NASA’s Modis instruments and
the International Polar Year ‘Polar View’ project
which uses the European Space Agency Envisat
satellite. Polar View operates to provide timely
images of the Antarctic sea ice and shelves to
assist science and operations in the Southern
Ocean. Further information and images are
available at www.polarview.aq
This discovery follows the recent UNEP report
that the world’s glaciers are continuing to melt
away. Data from 30 reference glaciers in nine
mountain ranges show that between the years
2004-2005 and 2005-2006 the average rate of
melting and thinning has more than doubled.
The Cambridge-based British Antarctic Survey
(BAS) is a world leader in research into global
environmental issues. With an annual budget of
around £40 million, five Antarctic Research
Stations, two Royal Research Ships and five
aircraft BAS undertakes an interdisciplinary
research programme and plays an active and
influential role in Antarctic affairs. BAS has
joint research projects with over 40 UK
universities and has more than 120 national and
international collaborations. It is a component
of the Natural Environment Research Council. More
information about the work of the Survey can be
found at: www.antarctica.ac.uk
———————————————————–