Subscribe free to our newsletters via your
. 24/7 Space News .




EARTH OBSERVATION
Tohoku Tsunami Created Icebergs In Antarctica
by Patrick Lynch for Goddard Space Flight Center
Greenbelt MD (SPX) Aug 09, 2011


Photos of the Sulzberger Ice Shelf illustrate the calving event associated with the Japan earthquake and resulting tsunami that occurred on March 11, 2011. The icebergs have just begun to separate in the left image. Credit: European Space Agency/Envisat. Before and after images and a movie are available at GSFC.

A NASA scientist and her colleagues were able to observe for the first time the power of an earthquake and tsunami to break off large icebergs a hemisphere away.

Kelly Brunt, a cryosphere specialist at Goddard Space Flight Center, Greenbelt, Md., and colleagues were able to link the calving of icebergs from the Sulzberger Ice Shelf in Antarctica following the Tohoku Tsunami, which originated with an earthquake off the coast of Japan in March 2011.

The finding, detailed in a paper published online in the Journal of Glaciology, marks the first direct observation of such a connection between tsunamis and icebergs.

The birth of an iceberg can come about in any number of ways. Often, scientists will see the towering, frozen monoliths break into the polar seas and work backwards to figure out the cause.

So when the Tohoku Tsunami was triggered in the Pacific Ocean on March 11 this spring, Brunt and colleagues immediately looked south. All the way south.

Using multiple satellite images, Brunt, Emile Okal at Northwestern University and Douglas MacAyeal at University of Chicago were able to observe new icebergs floating off to sea shortly after the sea swell of the tsunami reached Antarctica.

To put the dynamics of this event in perspective: An earthquake off the coast of Japan caused massive waves to explode out from its epicenter.

Swells of water swarmed toward an ice shelf in Antarctica, 8,000 miles (13,600 km) away, and about 18 hours after the earthquake occurred, those waves broke off several chunks of ice that together equaled about two times the surface area of Manhattan. According to historical records, this particular piece of ice hadn't budged in at least 46 years before the tsunami came along.

And as all that was happening, scientists were able to watch the Antarctic ice shelves in as close to real-time as satellite imagery allows, and catch a glimpse of a new iceberg floating off into the Ross Sea.

"In the past we've had calving events where we've looked for the source. It's a reverse scenario - we see a calving and we go looking for a source," Brunt said. "We knew right away this was one of the biggest events in recent history - we knew there would be enough swell. And this time we had a source."

Scientists first speculated in the 1970s that repeated flexing of an ice shelf - a floating extension of a glacier or ice sheet that sits on land - by waves could cause icebergs to break off. Scientific papers in more recent years have used models and tide gauge measurements in an attempt to quantify the impact of sea swell on ice shelf fronts.

The swell was likely only about a foot high (30 cm) when it reached the Sulzberger shelf. But the consistency of the waves created enough stress to cause the calving. This particular stretch of floating ice shelf is about 260 feet (80 meters) thick, from its exposed surface to its submerged base.

When the earthquake happened, Okal immediately honed in on the vulnerable faces of the Antarctic continent. Using knowledge of iceberg calving and what a NOAA model showed of the tsunami's projected path across the unobstructed Pacific and Southern oceans, Okal, Brunt and MacAyeal began looking at what is called the Sulzberger Ice Shelf. The Sulzberger shelf faces Sulzberger Bay and New Zealand.

Through a fortuitous break in heavy cloud cover, Brunt spotted what appeared to be a new iceberg in MODerate Imaging Spectroradiometer (MODIS) data.

"I didn't have strong expectations either way whether we'd be able to see something," Brunt said. "The fastest imagery I could get to was from MODIS Rapid Response, but it was pretty cloudy.

So I was more pessimistic that it would be too cloudy and we couldn't see anything. Then, there was literally one image where the clouds cleared, and you could see a calving event."

A closer look with synthetic aperture radar data from the European Space Agency satellite, Envisat, which can penetrate clouds, found images of two moderate-sized icebergs - with more, smaller bergs in their wake.

The largest iceberg was about four by six miles in surface area - itself about equal to the surface area of one Manhattan. All the ice surface together about equaled two Manhattans.

After looking at historical satellite imagery, the group determined the small outcropping of ice had been there since at least 1965, when it was captured by USGS aerial photography.

The proof that seismic activity can cause Antarctic iceberg calving might shed some light on our knowledge of past events, Okal said.

"In September 1868, Chilean naval officers reported an unseasonal presence of large icebergs in the southernmost Pacific Ocean, and it was later speculated that they may have calved during the great Arica earthquake and tsunami a month earlier," Okal said. "We know now that this is a most probable scenario."

MacAyeal said the event is more proof of the interconnectedness of Earth systems.

"This is an example not only of the way in which events are connected across great ranges of oceanic distance, but also how events in one kind of Earth system, i.e., the plate tectonic system, can connect with another kind of seemingly unrelated event: the calving of icebergs from Antarctica's ice sheet," MacAyeal said.

In what could be one of the more lasting observations from this whole event, the bay in front of the Sulzberger shelf was largely lacking sea ice at the time of the tsunami.

Sea ice is thought to help dampen swells that might cause this kind of calving. At the time of the Sumatra tsunami in 2004, the potentially vulnerable Antarctic fronts were buffered by a lot of sea ice, Brunt said, and scientists observed no calving events that they could tie to that tsunami.

"There are theories that sea ice can protect from calving. There was no sea ice in this case," Brunt said. "It's a big chunk of ice that calved because of an earthquake 13,000 kilometers away. I think it's pretty cool."

.


Related Links
-
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








EARTH OBSERVATION
Software on the Fly
Kelly Lake, Canada (SPX) Aug 09, 2011
Much of the activity that enables the Pavilion Lake Research Project (PLRP) to reach its scientific goals happens behind the scenes. In this latest post I'm going to talk a bit about the software glue, a system known as xGDS (Exploration Ground Data System), that enables PLRP's scientific success. Perhaps the most crucial set of scientific data generated by PLRP is video footage. For the f ... read more


EARTH OBSERVATION
"Big Splat" May Explain The Moon's Mountainous Far Side

LADEE Completes Mission Critical Design Review

Moon's mountains made by slo-mo crash: study

Unique volcanic complex discovered on Lunar far side

EARTH OBSERVATION
Opportunity On Final Rove To Endeavour Crater

Nearing First Landfall of Large Crater

Briny water may be at work in seasonal flows on Mars

Mars' northern polar regions in transition

EARTH OBSERVATION
Boeing Selects Atlas V Rocket for Initial Commercial Crew Launches

NASA funds 30 new space research projects

Welsh tech firm starting U.S. company

Invisibility cloak closer to reality

EARTH OBSERVATION
Toys for Tiangong

Why Tiangong is not a Station Hub

China to launch experimental satellite in coming days

Spotlight Time for Tiangong

EARTH OBSERVATION
Crew Stows Spacesuits, Completes Robotics Checkout

The Orbital Perspective of Astronaut Ron Garan

Voyage to Vaccine Discovery Continues with Space Station Salmonella Study

New uses for Space Station

EARTH OBSERVATION
Arianespace blasts another pair of satellites into orbit

Lockheed Martin-Built BSAT-3c/JCSAT-110R Satellite Launched Successfully For Japanese Firms

Ariane 5 ready for next heavy-lift flight

64 satellites launched by ISRO so far

EARTH OBSERVATION
Exoplanet Aurora Makes For An Out-of-this-World Sight

Distant planet aurorae modeled

Exoplanet Aurora: An Out-of-this-World Sight

Ten new distant planets detected

EARTH OBSERVATION
'Housekeeping' could solve space junk mess

Sony, Panasonic, Samsung in 3D glasses deal

Taiwan unveils eco-friendly rewritable 'paper'

Watermark ink device identifies unknown liquids instantly




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal 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. 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