Thanks
to Kristy Lewis
The
findings, announced in February, used ice velocity data to show that
there is a critical tipping point at which the shelves act like a
restraining band, holding back the the ice that flows toward the sea.
In a dramatic press release, the ESA said that as the ice is lost, it
could be “point of no return” for Antarctica’s ice.
Climate: Antarctic ice shelf retreat may be irreversible
30
April, 2016
ESA
satellites offer clues about climate change consequences
Staff
Report
An
analysis of data fromEuropean
Space Agencysatellites
shows that Antarctic ice shelves may be losing their buttressing role
as they get thinner and retreat inland.
The
findings, announced in February, used ice velocity data to show that
there is a critical tipping point at which the shelves act like a
restraining band, holding back the the ice that flows toward the sea.
In a dramatic press release, the ESA said that, if the ice is lost,
it could be “point of no return” for Antarctica’s ice.
The
ice shelves are huge and losing them would have serious implications
for global climate, speeding the rise of sea level. The Ross Ice
Shelf, for example, is the size of Spain and towers hundreds of
meters above sea level.
Some
of the vulnerable ice shelves have already started to thin and
crumble, including the 1995 collapse of the Larsen A ice shelf (about
the size of Berlin).
Seven years later the Larsen B Ice Shelf also
collapsed and scientists are currently documenting the disintegration
of the Wilkins Ice Shelf.
After
the Larsen B Ice Shelf cracked apart, tributary glaciers started
flowing eight times faster, increasing the amount of ice discharged
to the sea. At least 50 other shelves fringe the continent, some of
them much bigger than Larsen B.
The
recent analysis of the buttressing role of the shelves was done by
scientists with the University of Erlangen-Nuremberg Institute of
Geography and with the Laboratoire de Glaciologie et Géophysique de
l’Environnement in Grenoble. They used radar data from satellites
such as ESA’s ERS and Envisat. Their findings were published today
inNature
Climate Change.
About
13 percent of the total ice-shelf area consists of a passive part,
which simply floats and doesnt’t help hold back the land-based ice.
But behind the passively floating zone there is an area of ice the
researchers call a ‘safety band’, which is the most critical
portion of the ice shelf restraining the ice flow.
“For
some decades now satellite remote-sensing has allowed us to track
changes and movement of Antarctic ice fronts. In some regions we have
seen continuous ice-shelf recession,” said Dr .Johannes Fürst,
from the University of Erlangen-Nuremberg’s Institute of Geography.
“Once ice loss through the calving of icebergs goes beyond the
passive shelf ice and cuts into the safety band, ice flow towards the
ocean will accelerate, which might well entail an elevated
contribution to sea-level rise for decades and centuries to come.”
However,
there are some contrasting results across the continent as not all
ice shelves have this passive ice.
“The
Amundsen and Bellingshausen seas have limited or almost no passive
ice shelf, which implies that further retreat of current ice-shelf
fronts will have serious dynamic consequences,” Fürst said. “This
region is particularly vulnerable as ice shelves have already been
thinning at high rates for two decades.”
By
contrast, the Larsen C ice shelf in the Weddell Sea has a large
passive frontal area, where the calving of large tabular ice bergs
probably won’t speed up the flow of glaciers flowing toward the
sea.
The
findings will help improve projections for how the meltdown of
Antarctica’s ice shelves will play out as the globe warms up.
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