Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



EARTH OBSERVATION
Studies offer new glimpse of melting under Antarctic glaciers
by Staff Writers
Pasadena CA (JPL) Oct 27, 2016


A view from Operation IceBridge's aircraft of Crosson Ice Shelf, foreground. Mt. Murphy is in the background. Image courtesy NASA/OIB/Michael Studinger. For a larger version of this image please go here.

Two new studies by researchers at NASA and the University of California, Irvine (UCI), detect the fastest ongoing rates of glacier retreat ever observed in West Antarctica and offer an unprecedented direct view of intense ice melting from the floating undersides of glaciers. The results highlight how the interaction between ocean conditions and the bedrock beneath a glacier can influence the glacier's evolution, with implications for understanding future ice loss from Antarctica and global sea level rise.

The two studies examined three neighboring glaciers in West Antarctica that are melting and retreating at different rates. Smith, Pope and Kohler glaciers flow into the Dotson and Crosson ice shelves in the Amundsen Sea Embayment in West Antarctica, the part of the continent with the largest loss of ice mass.

A study led by Bernd Scheuchl of UCI, published in the journal Geophysical Research Letters on Aug. 28, used radar measurements from the European Space Agency's Sentinel-1 satellite and data from the earlier ERS-1 and ERS-2 satellites to look at changes in the glaciers' grounding lines - the boundary where a glacier loses contact with bedrock and begins to float on the ocean.

The grounding line is important because nearly all glacier melting takes place on the underside of the glacier's floating portion, called the ice shelf. If a glacier loses mass from enhanced melting, it may start floating farther inland from its former grounding line, just as a boat stuck on a sandbar may be able to float again if a heavy cargo is removed. This is called grounding line retreat.

Scheuchl's team found a rapid retreat of Smith Glacier's grounding line of 1.24 miles (2 kilometers) per year since 1996. Pope retreated more slowly at 0.31 mile (0.5 kilometer) per year since 1996. Kohler, which had retreated at a slower pace, actually readvanced a total of 1.24 miles (2 kilometers) since 2011.

These differences motivated Ala Khazendar of NASA's Jet Propulsion Laboratory, Pasadena, California - a coauthor of Scheuchl's study - to measure the ice losses at the bottoms of the glaciers, which he suspected might be underlying the changes in their grounding lines.

Khazendar's study, published Oct. 25 in the journal Nature Communications, used measurements of changes in the thickness and height of the ice from radar and laser altimetry instruments flown by NASA's Operation IceBridge and earlier NASA airborne campaigns.

Radar waves penetrate glaciers all the way to their base, allowing direct measurements of how the bottom profiles of the three glaciers at their grounding lines changed between 2002 and 2014. Laser signals reflect off the surface, so for the floating ice shelves, laser measurements of changes in surface elevation can be used to infer changes in ice thickness.

Previous studies using other techniques estimated the average melting rates at the bottom of Dotson and Crosson ice shelves to be about 40 feet per year (12 meters per year). Khazendar and his team, using their direct radar measurements, found stunning rates of ice loss from the glaciers' undersides on the ocean sides of their grounding lines.

The fastest-melting glacier, Smith, lost between 984 and 1,607 feet (300 and 490 meters) in thickness from 2002 to 2009 near its grounding line, or up to 230 feet per year (70 meters per year).

Those years encompass a period when rapid increases in mass loss were observed around the Amundsen Sea region. The regional scale of the loss made scientists strongly suspect that an increase in the influx of ocean heat beneath the ice shelves must have taken place.

"Our observations provide a crucial piece of evidence to support that suspicion, as they directly reveal the intensity of ice melting at the bottom of the glaciers during that period," Khazendar said.

"If I had been using data from only one instrument, I wouldn't have believed what I was looking at, because the thinning was so large," Khazendar added. However, the two IceBridge instruments, which use different observational techniques, both measured the same rapid ice loss.

Khazendar said Smith's fast retreat and thinning are likely related to the shape of the underlying bedrock over which it was retreating between 1996 and 2014, which sloped downward toward the continental interior, and oceanic conditions in the cavity beneath the glacier. As the grounding line retreated, warm and dense ocean water could reach the newly uncovered deeper parts of the cavity beneath the ice shelf, causing more melting.

As a result, "More sections of the glacier become thinner and float, meaning that the grounding line continues retreating, and so on," he said. The retreat of Smith might slow down as its grounding line has now reached bedrock that rises farther inland of the 2014 grounding line.

Pope and Kohler, by contrast, are on bedrock that slopes upward toward the interior.

The question remains whether other glaciers in West Antarctica will behave more like Smith Glacier or more like Pope and Kohler. Many glaciers in this sector of Antarctica are on beds that deepen farther inland, like Smith's.

However, Khazendar and Scheuchl said researchers need more information on the shape of the bedrock and seafloor beneath the ice, as well as more data on ocean circulation and temperatures, to be able to better project how much ice these glaciers will contribute to the ocean in a changing climate.

Scheuchl's study is titled "Grounding Line Retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, Measured with Sentinel-1a Radar Interferometry Data." It was published in Geophysical Research Letters. Khazendar's paper, titled "Rapid Submarine Ice Melting in the Grounding Zones of Ice Shelves in West Antarctica," was published in Nature Communications.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Operation IceBridge at NASA
Earth Observation News - Suppiliers, Technology and Application






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
EARTH OBSERVATION
NASA satellite sees sulfur dioxide diffuse across northern Iraq
Mosul, Iraq (UPI) Oct 25, 2016
Sulfur dioxide is emanating from a fire at a mine in northern Iraq. As new satellite images show, the noxious gas is diffusing across the region's lower atmosphere. The fire ignited last week at a sulfur extraction and processing facility near Mosul, Iraq. Since then, a plume of sulfur dioxide has grown in size. An image captured by NASA's Aqua satellite shows wind pushing the plume tow ... read more


EARTH OBSERVATION
No Balloons for JPL's Birthday, Just a 'Satelloon'

Urine may be the X factor to exploring deep space

US, Russian, Japanese astronauts return from ISS

Team braves wildlife, dust and darkness to find safe home for abandoned records

EARTH OBSERVATION
SpaceX zeroes in on helium containers for rocket explosion

Proven engine packs big, in-space punch for Space Launch System

Boosting Europe's all-electric satellites

Guiding Supply Ship to the International Space Station

EARTH OBSERVATION
Detailed images of Schiaparelli and its descent hardware on Mars

Cursed not, Difficult yes

Did it crash or land? Search on for Europe's Mars craft

Rover Conducting Science Investigations at 'Spirit Mount'

EARTH OBSERVATION
US, China hold second meeting on advancing space cooperation

China to enhance space capabilities with launch of Shenzhou-11

Ambitious space satellite projects set for liftoff

China's permanent station plans ride on mission

EARTH OBSERVATION
Dream coming true for ISS-bound rookie French astronaut

Airbus DS contracts with Intelsat General for European Defence Communications

Final exams prepare Thomas Pesquet for launch

Airbus DS in partnership with Orbital ATK to build EUTELSAT 5 West B

EARTH OBSERVATION
With new model, buildings may 'sense' internal damage

3-D-printed permanent magnets outperform conventional versions, conserve rare materials

New tech uses electricity to track water, ID potential problems in concrete

Nickel-78 is a doubly magic isotope supercomputer confirms

EARTH OBSERVATION
How Planets Like Jupiter Form

Giant Rings Around Exoplanet Turn in the Wrong Direction

Preferentially Earth-sized Planets with Lots of Water

Potential new hunting ground for exoplanets discovered

EARTH OBSERVATION
Last Bits of 2015 Pluto Flyby Data Received on Earth

Uranus may have two undiscovered moons

Possible Clouds on Pluto, Next Target is Reddish

Curious tilt of the Sun traced to undiscovered planet




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement