http://news.bbc.co.uk/2/hi/science/nature/3200450.stm
Last Updated: Friday,
17 October, 2003, 11:13 GMT 12:13 UK
BBC
South American glaciers' big melt
[ Picture
of Calvo Glacier in Chile... ]
CAPTION #1:
"A dramatic image looking down the Calvo Glacier in Chile"
[ Picture
of Lucia Glacier... ]
CAPTION #2:
"Lucia Glacier: Like many others its leading edge calves
into a lake"
The Patagonia glaciers of Chile and Argentina are melting so fast
they are making a significant contribution to sea-level rise,
say scientists.
They report ice was
lost at a rate sufficient to push up ocean
waters by 0.04 millimetres per year during the period from 1975
through to 2000.
This is equal, the
researchers say, to 9% of the total annual
global sea-level rise from all mountain glaciers.
The American research
team reports its findings in the journal Science.
Rising temperatures
The team combined data
from a space shuttle mission in 2000 and
survey data gathered on the ground to study the 63 largest Patagonia
ice fields.
They compared ice loss
rates between 1968 and 1975, and from
1975 to 2000. As well as the general increase in melting,
the team also found accelerated ice-mass loss between 1995
and 2000.
This period saw melting
sufficient to push up sea-levels
by 0.1 millimetres per year.
In comparison, the
team says, Alaska's glaciers, which cover
an area five times larger, account for about 30% of the total
annual global sea-level rise from mountain glaciers.
The researchers, led
by Eric Rignot, from the US space agency's
Jet Propulsion Laboratory, believe climate change has led to
the region experiencing a rise in air temperatures and decreased
precipitation.
Going backwards
Still, those factors
alone are not sufficient to explain the
rapid thinning.
The rest of the story
appears to lie primarily in the unique
dynamic response of the region's glaciers to climate change,
the researchers believe.
"The Patagonia
ice fields are dominated by so-called 'calving'
glaciers," Rignot said.
"Such glaciers
spawn icebergs into the ocean or lakes and have
different dynamics from glaciers that end on land and melt at
their front ends.
"Calving glaciers
are more sensitive to climate change once
pushed out of equilibrium, and make this region the fastest
area of glacial retreat on Earth," he said.
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