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![]() March 19, 2004 Patagonian Ice Dam Studied from Space, Cracks OpenA spectacle unseen for 16 years occurred in
Patagonia this week: a natural dam of blue ice
gave way to crushing lake waters trapped behind
it, finally breaking apart. Since last October this section � known as
Brazo Sur - had been blocked off from the rest of
the lake by the glacier’s flowing ice
tongue, which extended a solid wall of ice across
the narrow water channel. It is the subject of a long-term study by the
University of Innsbruck’s Institute for
Meteorology and Geophysics, with in-situ
observations supplemented by ESA satellite data.
“We also make use of radar imagery from ERS-2 and Envisat to monitor areas of accumulation and ablation and keep track of its position. “What makes Perito Moreno so interesting
to us is that it is one of the few Patagonian
glaciers that has advanced during recent days. It
dams the Brazo Sur on a periodic basis, the
previous time being 1988, then some 20 times
before that. It first occurred in 1917, and we
know it was the first time because a
several-hundred-year old forest was submerged as
a result.” Inevitably the total force the rising waters
exert upon the glacier becomes too much. On 12
March 2004 water began to drain through
subsurface fissures, which enlarged into a
tunnel. Two days later the ice fractured above
the waterline. Sightseers flocked to watch the
ice dam give way, a sight which some had feared
might never be seen this century due to global
warming. “Field studies of mass fluxes,
complemented by satellite radar, record 5.5
meters (216.5 inches) of precipitation falling on
the accumulation zone a year, equivalent to about
15 meters (590.6 inches) of consolidated snow.
“This feature of subglacial topography,
as well as the comparatively high elevation of
the accumulation area, means that is it less
vulnerable to changing conditions, such as warmer
climate that has led most glaciers in the region
to recede significantly during the last 30 years.
Following the fracture, the Innsbruck
University team will continue to monitor glacial
motion and flux across Southern Patagonia - a
region containing the largest glaciers in the
southern hemisphere outside of Antarctica. Henri Laur This text derived from http://www.esa.int/esaSA/SEM2OFX5WRD_earth_0.html Recommend this Article to a Friend Back to: News |
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