Antarctica is About to Lose a 2,000 Square Mile Chunk of Ice — And it Could Mean the End of the Larsen C Ice Shelf
10
January, 2017
It’s
happened before. Ice shelves on the northern Antarctic Peninsula
released large chunks of ice into the Southern Ocean as the world
warmed up. They developed a concave shape which became unstable. Then
they collapsed.
The
ultimate collapse of Larsen A occurred in 1995. In 2002, further up
the Antarctic Peninsula, the larger Larsen B Ice Shelf succumbed to
the same fate. And it is thought that such losses haven’t happened
to this section of Antarctica in at least 11,000 years and possibly
as long ago as 100,000 years.
(NASA’s Jet
Propulsion Laboratory provides
this narrative describing the collapse of the Larsen B Ice Shelf in
2002. Video source: JPL.)
But
in the present world, one where human fossil fuel emissions have
forced global temperatures above 1 C hotter than 1880s averages, the
stability of many of the great great ice shelves is now endangered.
Larsen
C Ice Shelf to Calve 2,000 Square Mile Iceberg
Today,
a huge rift has nearly bisected a large frontal section of the Larsen
C Ice shelf — an ice system many times the size of its now deceased
companions Larsen A and Larsen B. And during December — a period
when Antarctica was warming into Austral Summer — this
massive crack grew by 18 kilometers.
When,
and not if, the crack reaches the ocean, a 2,000 square mile ice berg
will float away from Larsen C. It will be one of the largest ice
bergs ever to form in human memory. One the size of the state of
Delaware. It will tower hundreds of feet above the ocean surface. And
it will last for years before ultimately melting.
(The
Larsen C is rift grew considerably — both lengthening and widening
during December of 2016. It was an indication that a massive ice berg
was about to break off. Image source: MIDAS.)
This
event will change the geography of our world. And for this alteration
alone, it has great consequence. But, as
Chris Mooney notes in this excellent Washington Post article on the
subject,
it’s what happens afterward that really counts.
Event
Could Presage Total Collapse
Of
concern is the fact that once this massive ice berg calves off of
Larsen C, the great ice sheet may become unstable. It will take on a
concave form. This form will make it more vulnerable to further melt
by warming waters running in toward the shelf. Furthermore, the large
ice berg will take a chunk of Larsen C’s compressive arch with it.
Such a compressive arch — like the arch of a flying buttress —
helps to bear the weight of the shelf and keep it from smashing into
thousands of tiny pieces. If too much of the arc is lost, the shelf
can’t survive for long.
(Researchers
at The
MIDAS Project have
projected that a 2,000 square mile section of the Larsen C Ice Shelf
is about to break off. This section represents 10 percent of the
Larsen C system. Its loss risks destabilization of the entire ice
shelf. If Larsen C does disintegrate, it will release glaciers
capable of increasing global sea level by another 4 inches. Image
source: MIDAS.)
Glaciologist
Eric Rignot notes in The
Washington Post:
“We studied the current rift in the past few years, it has been progressing rather ‘normally,’ the recent acceleration in the rift progression is ‘expected’ in my opinion. The consequences on the rest of the ice shelf are not clear at this point. If the calving continues and goes past the compressive arch … then the ice shelf will break up.”
Scientists
are currently divided over the issue of whether or not Larsen C’s
near-term demise is imminent. However, the loss of such a massive ice
berg from Larsen C, the present human-forced warming of the Antarctic
land and ocean environment, and the presently observed thinning of
the ice shelf all point toward a rising risk of destabilization or
disintegration.
As
with most things geological, you can’t really say that such an
event is certain until after the fact. But as for Larsen C’s
prospects of long term survival, things aren’t looking too great at
the moment.
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