[meteorite-list] NASA Study Shows Antarctica's Larsen B Ice Shelf Nearing Its Final Act

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 18 May 2015 16:13:17 -0700 (PDT)
Message-ID: <201505182313.t4INDHWs004597_at_zagami.jpl.nasa.gov>

May 14, 2015

RELEASE 15-092

NASA Study Shows Antarctica's Larsen B Ice Shelf Nearing Its Final Act

A new NASA study finds the last remaining section of Antarctica's Larsen B
Ice Shelf, which partially collapsed in 2002, is quickly weakening and likely
to disintegrate completely before the end of the decade.

A team led by Ala Khazendar of NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, California, found the remnant of the Larsen B Ice Shelf is flowing
faster, becoming increasingly fragmented and developing large cracks. Two of
its tributary glaciers also are flowing faster and thinning rapidly.

"These are warning signs that the remnant is disintegrating," Khazendar said.
"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."

Ice shelves are the gatekeepers for glaciers flowing from Antarctica toward
the ocean. Without them, glacial ice enters the ocean faster and accelerates
the pace of global sea level rise. This study, the first to look
comprehensively at the health of the Larsen B remnant and the glaciers that
flow into it, has been published online in the journal Earth and Planetary
Science Letters.

Khazendar's team used data on ice surface elevations and bedrock depths from
instrumented aircraft participating in NASA's Operation IceBridge, a
multiyear airborne survey campaign that provides unprecedented documentation
annually of Antarctica's glaciers, ice shelves and ice sheets. Data on flow
speeds came from spaceborne synthetic aperture radars operating since 1997.

Khazendar noted his estimate of the remnant's remaining life span was based
on the likely scenario that a huge, widening rift that has formed near the
ice shelf's grounding line will eventually crack all the way across. The
free-floating remnant will shatter into hundreds of icebergs that will drift
away, and the glaciers will rev up for their unhindered move to the sea.

Located on the coast of the Antarctic Peninsula, the Larsen B remnant is
about 625 square miles (1,600 square kilometers) in area -- roughly the size
of Lake Superior and Lake Michigan combined -- and about 1,640 feet (500
meters) thick at its thickest point. Its three major tributary glaciers are
fed by their own tributaries farther inland.

"What is really surprising about Larsen B is how quickly the changes are
taking place," Khazendar said. "Change has been relentless."

The remnant's main tributary glaciers are named Leppard, Flask and Starbuck
-- the latter two after characters in the novel Moby Dick. The glaciers'
thicknesses and flow speeds changed only slightly in the first couple of
years following the 2002 collapse, leading researchers to assume they
remained stable. The new study revealed, however, that Leppard and Flask
glaciers have thinned by 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 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 eightfold - comparable to a car accelerating from 55
to 440 mph.

The third and smallest glacier, Starbuck, has changed little. Starbuck's
channel is narrow compared with those of the other glaciers, and strongly
anchored to the bedrock, which, according to authors of the study, explains
its comparative stability.

"This study of the Antarctic Peninsula glaciers provides insights about how
ice shelves farther south, which hold much more land ice, will react to a
warming climate," said JPL glaciologist Eric Rignot, a coauthor of the paper.

The research team included scientists from JPL, the University of California,
Irvine, and the University Centre in Svalbard, Norway. The paper is online
at:

http://go.nasa.gov/1bbpfsC

NASA uses the vantage point of space to increase our understanding of our
home planet, improve lives and safeguard our future. NASA develops new ways
to observe and study Earth's interconnected natural systems with long-term
data records. The agency freely shares this unique knowledge and works with
institutions around the world to gain new insights into how our planet is
changing.

For more information about NASA???s Earth science activities, visit:

http://www.nasa.gov/earth

-end-
Received on Mon 18 May 2015 07:13:17 PM PDT