Africa Water, Sanitation & Hygiene Africa water, Sanitation May-June2015 Vol. 10 No.3 | Page 35

Climate Change

Major Antarctic Ice Shelf May Disappear by 2020
By Jenna Iacurci

Pictured: Larsen B Ice Shelf following the 2002 collapse.
(Photo : MODIS, NASA’s Earth Observatory)
With climate change heating things up, and the Earth’s
poles rapidly melting, it should come as no surprise that
a major Antarctic ice shelf may completely disappear by
2020, according to a new NASA study.
The last remaining section of the Larsen B Ice Shelf, which
partially collapsed in 2002, is quickly weakening, flowing
faster, and becoming more and more fragmented as well
as developing large cracks. This, plus the fact that two of
its tributary glaciers are also flowing faster and thinning
rapidly, does not bode well for the ice shelf.
“These are warning signs that the remnant is
disintegrating,” Ala Khazendar of NASA’s Jet Propulsion
Laboratory (JPL) in Pasadena, Calif., who led the
study, said in a news release. “Although it’s fascinating
scientifically to have a front-row seat to watch the ice shelf
becoming unstable and breaking up, it’s bad news for our
planet. This ice shelf has existed for at least 10,000 years,
and soon it will be gone.”
This news directly follows research published just recently
that a neighboring ice shelf, called the Larsen C Ice Shelf,
is simultaneously thinning from above and below.
Ice shelves such as these are extremely important because
they prevent Antarctic glaciers from flowing out to sea and
dumping massive amounts of freshwater into the ocean.
Without ice shelves like the Larsen B Ice Shelf, the rate of
global sea level rise will quickly accelerate.
To better understand the consequences of climate
change in the future, this latest NASA study took the
first comprehensive look at the health of the Larsen B
remnant and the glaciers that flow into it. The results
were published in the journal Earth and Planetary Science
Letters.
Khazendar’s team used data collected by aircraft measuring
ice surface elevations and bedrock depths as part of an
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Africa Water, Sanitation & Hygiene • May - June 2015

annual NASA survey campaign. Data on flow speeds came
from spaceborne synthetic aperture radars operating since
1997.
The scientists predicted that the Larsen B Ice Shelf will
completely disappear by 2020 - that is, assuming that the
huge, widening rift that has formed near its grounding line
will crack all the way across, a likely future scenario. The
free-floating remnant will shatter into hundreds of icebergs
that will drift away, and the glaciers will have nothing to
stop them from moving out to sea.
Currently, the Larsen B remnant, located on the coast
of the Antarctic Peninsula, is about 625 square miles
(1,600 square
kilometers) in
area and about
1,640 feet
(500 meters)
thick at its
thickest point.
However,
these
dimensions
(Photo : NSIDC/Ted Scambos) are expected
to shrink
further and further as the climate continues to warm.
“What is really surprising about Larsen B is how quickly
the changes are taking place,” Khazendar said. “Change
has been relentless.”
The scientists fear that the cracking of the shelf could see
its three glaciers - named Leppard, Flask and Starbuck accelerate rapidly towards the ocean. In the first couple of
years following the 2002 collapse, the glaciers’ thicknesses
and flow speeds changed only slightly, leading experts
to believe that they were stable. However, the new study
reveals that that’s not the case.
The Leppard and Flask glaciers have thinned by a
staggering 65-72 feet (20-22 meters) and accelerated
considerably in the intervening years. The fastest-moving
part of Flask Glacier had accelerated 36 percent by 2012 to
a flow speed of 2,300 feet (700 meters) a year - comparable
to a car accelerating from 55 to 75 mph.
Flask’s acceleration, while the Larsen B remnant has been
weakening, may be just a preview of what will happen
when the remnant breaks up completely. After the 2002
Larsen B collapse, the glaciers behind the collapsed part of
the shelf accelerated as much as eight-fold.
Much of Antarctica is melting faster than ever, and Arctic
sea ice is also projected to disappear completely in our
lifetime, and these phenomena paint a bleak future in
terms of global sea level rise as a result of climate change.