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Huge cavity in the Antarctic glacier signals rapid decay

A gigantic cave
– two thirds of the surface of Manhattan and almost 300 meters high – growing
at the foot of the Thwaites Glacier in West Antarctic is one of several
disturbing discoveries reported in a new NASA-led study of decay
Glacier. The results emphasize the need for detailed observations of the Antarctic
Bottoms of the glaciers in calculating how fast the global sea level will rise
Answer to climate change.

It is expected that some gaps between ice and rocks will be found between Thwaites & # 39; soil
Seawater could invade the glacier and melt from below. The size and
However, the explosive growth rate of the newly discovered hole surprised her. It is big
enough to contain 1

4 billion tons of ice, and most of this ice melted
the last three years.

"We have
For years it has been suspected that Thwaites was not firmly connected to the underground
including, "said Eric Rignot of the University of California, Irvine and
NASA's Jet Propulsion Laboratory in Pasadena, California. Rignot is a co-author
the new study published today in Science Advances. "Many Thanks
With a new generation of satellites, we can finally see the detail, "he said

The cavity was
Discovered by ice-penetrating radar during NASA's operation
an airborne campaign starting in 2010 and exploring connections
between the polar regions and the global climate. The researchers also used
Data from a constellation of Italian
and German
Spaceborne synthetic aperture radar. This very high-resolution data can be
processed by a technique called radar interferometry to reveal the soil
Surface below has moved between the pictures.

"[The size
of] A cavity under a glacier plays an important role in melting," he said
The lead author of the study, Pietro Milillo of JPL. "Because more heat and water come
it melts faster under the glacier. "

Models of ice sheets use a solid form to represent a cavity under the ice.
instead of changing the cavity and allowing it to grow. The new discovery implies that this limitation is likely to affect these models
Underestimate how quickly Thwaites loses ice.

About the size
from Florida, Thwaites Glacier is currently responsible for about 4
Percent of global sea level rise. It contains enough ice to raise the world ocean
just over 2 feet (65 centimeters) and behind the neighboring glacier
The sea level would increase the sea level by another 2.4m if it were all ice

Thwaites is one
To reach the most difficult places on earth, but it will soon become known
than ever before. The US National Science Foundation and British National
The Environmental Research Council launches a five-year field project to respond
the most critical questions about his processes and functions. The International
Thwaites Glacier Collaboration
begins field trials in
the summer of the southern hemisphere 2019-20.

How scientists measure ice loss

There is no way
Monitor Antarctic glaciers in the long term from the ground. Instead,
Scientists use satellite data or airborne instruments to observe their characteristics
When a glacier melts, change the speed, eg. B. flow rate and surface height.

The peculiarity of the glacier is the grounding line of a glacier – the place on the edge of the glacier
Continent, where it rises from the ground and begins to float in the seawater. Many Antarctic
The glaciers extend far beyond their grounding lines and float over them
Open ocean.

Just like one
a grounded boat can swim again when the weight of its cargo is removed, a
Glacier that loses ice can float over land where it used to stick. When
In this case, the grounding line retreats inland. That's more
The bottom of the glacier to seawater increases the likelihood that its melting rate will increase

An irregular retreat

For Thwaites
"We are discovering different retraction mechanisms," said Millilo.
Different processes in different parts of the 100 miles long (160 kilometers long)
In front of the glacier put the lines of retreat for the earth line and the ice
Loss of synchronization.

The huge cavity
is located under the main trunk of the glacier on its west side – the side further
from the West Antarctic Peninsula. In this region, when the tide rises and falls,
The ground line retreats and advances over a zone of about 2 to 3 miles (3
up to 5 kilometers). The glacier has broken away from a ridge in the valley
Bedrock at a constant rate of about 0.6 to 0.8 kilometers a
Year since 1992. Despite this stable rate of return of the earthing cables melts the
The rate on this side of the glacier is extremely high.

"In the East
Side of the glacier, the retreat of the ground line passes through small channels,
maybe a mile wide, like fingers reaching under the glacier to melt it
from below, "said Milillo, in which region the speed of the grounding line
The retreat doubled from 0.6 miles a year from 1992 to 2011
to 1.2 miles per year from 2011 to 2017. Also with this acceleration
Retreat, however, the melting rates on this side of the glacier are lower than on the
West side.

These results
emphasize that the interactions between ice and ocean are more complex than before
Roger that.

Milillo hopes
The new results will be useful for the international Thwaites Glacier
Collaboration researchers prepare for their fieldwork. "Such data is
It is essential that the local parties focus on the areas where the measure is located
The grounding line quickly contracts with complex spatial patterns. "

The details of how the ocean melts away from this glacier are essential for the projection
its impact on sea-level rise in the coming decades, "said Rignot.

The paper by Milillo and his co-authors in the journal Science Advances bears the title "Heterogeneous Retreat and Ice Melting"
Thwaites Glacier, West Antarctic. "Co-authors were from the University of
California, Irvine; the German Aerospace Center in Munich, Germany; and the
University of Grenoble Alpes in Grenoble, France.

Media contact

Esprit Smith
Jet Propulsion Laboratory, Pasadena, California
[email protected]

Brian Bell
University of California, Irvine
[email protected]

Written by Carol Rasmussen
Earth Science News Team of NASA


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