Wilkins Antarctic ice shelf breaking up- unprecedented rate.
26/3/2008 The Independent. Wilkins is one of the biggest in Antarctica and, for the past century, the massive Wilkins ice shelf appeared to have escaped the ravages of global warming. But now, enormous cracks have appeared in this floating ice platform the size of
Northern Ireland. Scientists say it is breaking apart at an unprecedented rate
after warmer temperatures weakened it.
A thin strip of ice is all that now prevents the Wilkins shelf from
disintegrating and breaking away from the landmass of the Antarctic peninsula,
scientists said yesterday. The peninsula is the fastest-warming region in the
Antarctic and has seen some of the largest temperature rises on earth – 0.5C per
decade – which is why the Wilkins ice shelf is on the verge of disappearing
completely, said one of the scientists.
Observers at the British Antarctic Survey (BAS) in Cambridge and the US National
Snow and Ice Data Centre in Colorado said they were astonished to discover just
how fast the ice shelf was breaking apart since the first cracks were seen in
February.
“Wilkins is the largest ice shelf yet on the Antarctic peninsula to be
threatened, said David Vaughan of the BAS. “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.
“In this case things are happening more rapidly than we thought. We didn’t
really understand how sensitive these ice shelves are to climate change,” said
Dr Vaughan, who predicted in the 1990s that it would take 30 years for the ice
shelf to break up.
Ice shelves form along the coasts and, because the ice is already floating on
water, their disintegration does not affect sea levels. However, scientists
believe that their rapid disappearance could lead to the faster movement into
the ocean of the massive, land-based ice sheets and glaciers – which do raise
sea levels.
The Wilkins ice shelf covers an area of about 5,282 square miles and satellite
images taken at the end of February revealed that the rapid disintegration began
after an iceberg the size of the Isle of Man broke away from its western edge.
Ted Scambos, of the snow and ice data centre, spotted the development and
alerted colleagues at the BAS in Cambridge, who immediately dispatched a Twin
Otter reconnaissance aircraft to map the Wilkins ice shelf with aerial
photographs.
“I had never seen anything like this before – it was awesome,” said Jim Elliott,
who was on board the aircraft. “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, looked as though they’ve been thrown around like rubble – it was
like an explosion.”
Dr Scambos said: “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… the collapse underscores that the Wilkins region has experienced an
intense melt season. Regional sea ice has all but vanished, leaving the ice
shelf exposed to the action of waves.”
Several ice shelves on the peninsula have retreated in recent years and six of
them – the Prince Gustav Channel, Larsen Inlet, Larsen A and Larsen B, the
Wordie, Muller and the Jones ice shelves – have collapsed completely.
The Wilkins ice shelf is important because it is farther south on the Antarctic
peninsula, where temperatures are generally colder than at the northern tip.
“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,” Dr Vaughan said.
“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.”
The two biggest ice shelves in Antarctica – the Ross and the Ronne – lie on the
edges of the Antarctic mainland farther south and so far show no signs of
melting, Dr Vaughan added.