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Archive for the ‘Antarctica’ Category

What in the Ocean Are Hydrothermal Vents?

Posted by feww on March 4, 2010

Press Resources | Latest News
The Earth Institute/ Columbia University

Scientists Locate Apparent Hydrothermal Vents off Antarctica

Discovery, a First, Could Spur Exploration of Distant Mid-Ocean Ridge

Scientists at Columbia’s Lamont-Doherty Earth Observatory have found evidence of hydrothermal vents on the seafloor near Antarctica, formerly a blank spot on the map for researchers wanting to learn more about seafloor formation and the bizarre life forms drawn to these extreme environments.

Hydrothermal vents spew volcanically heated seawater from the planet’s underwater mountain ranges—the vast mid-ocean ridge system, where lava erupts and new crust forms. Chemicals dissolved in those vents influence ocean chemistry and sustain a complex web of organisms, much as sunlight does on land. In recent decades more than 220 vents have been discovered worldwide, but so far no one has looked for them in the rough and frigid waters off Antarctica.

A vent spews chemical fluids from the East Pacific Rise, about 5,600 miles from newly suspected vents on the Pacific Antarctic Ridge.
Credit: Woods Hole Oceanographic Institution.


From her lab in Palisades, N.Y., geochemist Gisela Winckler recently took up the search. By analyzing thousands of oceanographic measurements, she and her Lamont colleagues pinpointed six spots on the remote Pacific Antarctic Ridge, about 2,000 miles from New Zealand, the closest inhabited country, and 1,000 miles from the west coast of Antarctica, where they think vents are likely to be found. The sites are described in a paper published THIS WEEK in the journal Geophysical Research Letters.

“Most of the deep ocean is like a desert, but these vents are oases of life and weirdness,” said Winckler. “The Pacific Antarctic ridge is one of the ridges we know least about. It would be fantastic if researchers were to dive to the seafloor to study the vents we believe are there.”

Two important facts helped the scientists isolate the hidden vents. First, the ocean is stratified with layers of lighter water sitting on top of layers of denser water. Second, when a seafloor vent erupts, it spews gases rich in rare helium-3, an isotope found in earth’s mantle and in the magma bubbling below the vent. As helium-3 disperses through the ocean, it mixes into a density layer and stays there, forming a plume that can stretch over thousands of kilometers.

The Lamont scientists were analyzing ocean-helium measurements to study how the deep ocean exchanges dissolved gases with the atmosphere when they came across a helium plume that looked out of place. It was in a southern portion of the Pacific Ocean, below a large and well-known helium plume coming off the East Pacific Rise, one of the best-studied vent regions on earth. But this mystery plume appeared too deep to have the same source.

Suspecting that it was coming from the Pacific Antarctic Ridge instead, the researchers compiled a detailed map of ocean-density layers in that region, using some 25,000 salinity, temperature and depth measurements. After locating the helium plume along a single density layer, they compared the layer to topographic maps of the Pacific Antarctic Ridge to figure out where the plume would intersect.

The Pacific Antarctic Ridge may be the least-studied of the underwater volcanic mountains that crisscross the globe. Blue square indicates suspected vents.
Credit: Modified image from Chris German and Karen Von Damm.

The sites they identified cover 340 miles of ridge line–the approximate distance between Manhattan and Richmond, Va.–or about 7 percent of the total 4,300 mile-ridge. This chain of volcanic mountains lies about three miles below the ocean surface, and its mile-high peaks are cut by steep canyons and fracture zones created as the sea floor spreads apart. It is a cold and lonely stretch of ocean, far from land or commercial shipping lanes.

“They haven’t found vents, but they’ve narrowed the places to look by quite a bit,” said Edward Baker, a vent expert at the National Oceanic and Atmospheric Administration.

Of course, finding vents in polar waters is not easy, even with a rough idea where to look. In 2007, Woods Hole Oceanographic Institution geophysicist Rob Reves-Sohn led a team of scientists to the Gakkel Ridge between Greenland and Siberia to look for vents detected six years earlier. Although they discovered regions where warm fluids appeared to be seeping from the seafloor, they failed to find the high-temperature, black smoker vents they had come for.  In a pending paper, Sohn now says he has narrowed down the search to a 400-kilometer-square area where he expects to find seven new vents, including at least one black smoker.

The search for vents off Antarctica may be equally unpredictable, but the map produced by the Lamont scientists should greatly improve the odds of success, said Robert Newton, a Lamont oceanographer and study co-author. “You don’t have to land right on top of a vent to know it’s there,” he said. “You get a rich mineral soup coming out of these smokers—methane, iron, manganese, sulfur and many other minerals. Once you get within a few tens of kilometers, you can detect these other tracers.”

Since the discovery of the first hydrothermal vents in the late 1970s, scientists have searched for far-flung sites, in the hunt for new species and adaptive patterns that can shed light on how species evolved in different spots. Cindy Van Dover, a deep sea biologist and director of the Duke University Marine Laboratory, says she expects that new species will be found on the Pacific Antarctic Ridge, and that this region may hold important clues about how creatures vary between the Indian and Pacific Oceans, on either end.

“These vents are living laboratories,” said Van Dover, who was not involved in the study. “When we went to the Indian Ocean, we discovered the scaly-foot gastropod, a deep-sea snail whose foot is covered in armor made of iron sulfides. The military may be interested in studying the snail to develop a better armor. The adaptations found in these animals may have many other applications.”

Other study authors include Peter Schlosser, head of Lamont’s Environmental Tracer Group and Lamont marine geologist Timothy Crone.

Posted in Antarctica, East Pacific Rise, Gakkel Ridge, geochemistry, Pacific Antarctic Ridge, underwater mountain ranges | Tagged: , , , | 1 Comment »

The Great Antarctic Peninsula Ice Shelf Extinction

Posted by feww on February 23, 2010

Public Release: USGS

Ice shelves disappearing on Antarctic Peninsula

Glacier retreat and sea level rise are possible consequences

Ice shelves are retreating in the southern section of the Antarctic Peninsula due to climate change. This could result in glacier retreat and sea-level rise if warming continues, threatening coastal communities and low-lying islands worldwide.

Click Images to Enlarge!


Southern Portion of Antarctic Peninsula. This image identifies the southern portion of the Antarctic Peninsula, which is one area studied as part of this project. Research on the southern Antarctic Peninsula is summarized in the USGS report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” (map I—2600—C). Source: U.S. Geological Survey


Multi-year ice. ARCTIC OCEAN – A multi-year ice floe slides down the starboard side of the Coast Guard Cutter Healy Aug. 11, 2009, as the ship heads north into even thicker ice. “You can tell that this is a multi-year ice floe by the light blue melt ponds that have formed on top of the floe,” said Pablo Clemente-Colón, chief scientist at the U.S. National Ice Center. Credit: Patrick Kelley, U.S. Coast Guard


Southern Antarctic Peninsula. This image shows ice-front retreat in part of the southern Antarctic Peninsula from 1947 to 2009. The southern portion of the Antarctic Peninsula is one area studied as part of this project, and is summarized in the USGS report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” (map I—2600—C). Source: U.S. Geological Survey

U.S. Geological Survey says its research is the first to document that every ice front in the southern part of the Antarctic Peninsula has been retreating overall from 1947 to 2009, with the most dramatic changes occurring since 1990. The USGS previously documented that the majority of ice fronts on the entire Peninsula have also retreated during the late 20th century and into the early 21st century.

The ice shelves are attached to the continent and already floating, holding in place the Antarctic ice sheet that covers about 98 percent of the Antarctic continent. As the ice shelves break off, it is easier for outlet glaciers and ice streams from the ice sheet to flow into the sea. The transition of that ice from land to the ocean is what raises sea level.

“This research is part of a larger ongoing USGS project that is for the first time studying the entire Antarctic coastline in detail, and this is important because the Antarctic ice sheet contains 91 percent of Earth’s glacier ice,” said USGS scientist Jane Ferrigno. “The loss of ice shelves is evidence of the effects of global warming. We need to be alert and continually understand and observe how our climate system is changing.”

The Peninsula is one of Antarctica’s most rapidly changing areas because it is farthest away from the South Pole, and its ice shelf loss may be a forecast of changes in other parts of Antarctica and the world if warming continues.

Retreat along the southern part of the Peninsula is of particular interest because that area has the Peninsula’s coolest temperatures, demonstrating that global warming is affecting the entire length of the Peninsula.

The Antarctic Peninsula’s southern section as described in this study contains five major ice shelves: Wilkins, George VI, Bach, Stange and the southern portion of Larsen Ice Shelf. The ice lost since 1998 from the Wilkins Ice Shelf alone totals more than 4,000 square kilometers, an area larger than the state of Rhode Island.

The USGS is working collaboratively on this project with the British Antarctic Survey, with the assistance of the Scott Polar Research Institute and Germany’s Bundesamt fűr Kartographie und Geodäsie. The research is also part of the USGS Glacier Studies Project, which is monitoring and describing glacier extent and change over the whole planet using satellite imagery.

Related Info:

Contact: Jessica Robertson
jrobertson@usgs.gov
United States Geological Survey

Related Links:

Posted in Antarctic Peninsula, Antarctica, Ice Shelf, Larsen Ice Shelf | Tagged: , , , , , , , | Leave a Comment »

WILKINS ICE SHELF IS “HANGING BY A THREAD”

Posted by feww on January 20, 2009

Antarctic ice shelf set to collapse due to warming

By Alister Doyle, Environment Correspondent

Tue Jan 20, 2009 8:42am EST

WILKINS ICE SHELF, Antarctica (Reuters) – A huge Antarctic ice shelf is on the brink of collapse with just a sliver of ice holding it in place, the latest victim of global warming that is altering maps of the frozen continent.


Between 1981 and 2007, most of Antarctica warmed. Portions of West Antarctica experienced an especially rapid rise in temperature. (NASA image by Robert Simmon, based on data from Joey Comiso, GSFC.)

“We’ve come to the Wilkins Ice Shelf to see its final death throes,” David Vaughan, a glaciologist at the British Antarctic Survey (BAS), told Reuters after the first — and probably last — plane landed near the narrowest part of the ice.

The flat-topped shelf has an area of thousands of square kilometers, jutting 20 meters (65 ft) out of the sea off the Antarctic Peninsula.

But it is held together only by an ever-thinning 40-km (25-mile) strip of ice that has eroded to an hour-glass shape just 500 meters wide at its narrowest.

In 1950, the strip was almost 100 km wide.

“It really could go at any minute,” Vaughan said on slushy snow in bright sunshine beside a red Twin Otter plane that landed on skis. He added that the ice bridge could linger weeks or months.

The Wilkins once covered 16,000 sq km (6,000 sq miles). It has lost a third of its area but is still about the size of Jamaica or the U.S. state of Connecticut. Once the strip breaks up, the sea is likely to sweep away much of the remaining ice.

Icebergs the shape and size of shopping malls already dot the sea around the shelf as it disintegrates. Seals bask in the southern hemisphere summer sunshine on icebergs by expanses of open water.


High-resolution satellite data show the Wilkins Ice Shelf collapse in detail, including blocks of ice that have tipped over and blocks of ice that have remained upright. (Formosat image © 2008 Dr. Cheng-Chien Liu, National Cheng-Kung University and Dr. An-Ming Wu, National Space Organization, Taiwan.)

A year ago, BAS said the Wilkins was “hanging by a thread” after an aerial survey. “Miraculously we’ve come back a summer later and it’s still here. If it was hanging by a thread last year, it’s hanging by a filament this year,” Vaughan said.

Nine other shelves have receded or collapsed around the Antarctic peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002. The trend is widely blamed on climate change caused by heat-trapping gases from burning fossil fuels.

WARMING TO BLAME

“This ice shelf and the nine other shelves that we have seen with a similar trajectory are a consequence of warming,” Vaughan said.

In total, about 25,000 sq km of ice shelves have been lost, changing maps of Antarctica. Ocean sediments indicate that some shelves had been in place for at least 10,000 years.


Early in the day on February 28, 2008, the Wilkins Ice Shelf remained intact. By March 17, 2008, the ice shelf had retreated significantly from its original extent. As the Antarctic summer drew to a close, sea ice began to freeze around the ice fragments. (NASA images by Jesse Allen and Robert Simmon, based on MODIS data.)

Vaughan stuck a GPS monitoring station on a long metal pole into the Wilkins ice on behalf of Dutch scientists. It will track ice movements via satellite.

The shelf is named after Australian George Hubert Wilkins, an early Antarctic aviator who is set to join an exclusive club of people who have a part of the globe named after them that later vanishes.

Loss of ice shelves does not raise sea levels significantly because the ice is floating and already mostly submerged by the ocean. But the big worry is that their loss will allow ice sheets on land to move faster, adding extra water to the seas.


Large blocks of ice, recently broken off the Wilkins Ice Shelf, float on the ocean in this aerial photograph. In between the large blocks of ice float much smaller pieces of ice with a rough surface. (Photograph © 2008 British Antarctic Survey.)

Wilkins has almost no pent-up glaciers behind it. But ice shelves further south hold back vast volumes of ice. “When those are removed the glaciers will flow faster,” Vaughan said.

Temperatures on the Antarctic Peninsula have warmed by about 3 Celsius (5.4 Fahrenheit) since 1950, the fastest rise in the southern hemisphere. There is little sign of warming elsewhere in Antarctica.

BAS scientists and two Reuters reporters stayed about an hour on the shelf at a point about 2 km wide.

“It’s very unlikely that our presence here is enough to initiate any cracks,” Vaughan said. “But it is likely to happen fairly soon, weeks to months, and I don’t want to be here when it does.”

The U.N. Climate Panel, of which Vaughan is a senior member, projected in 2007 that world sea levels were likely to rise by between 18 and 59 cm (7 and 23 inches) this century.

But it did not factor in any possible acceleration of ice loss from Antarctica. Even a small change in the rate could affect sea levels, and Antarctica’s ice sheets contain enough water in total to raise world sea levels by 57 meters.

About 190 nations have agreed to work out a new U.N. treaty by the end of 2009 to slow global warming, reining in emissions from burning fossil fuels in power plants, cars and factories.

Following are facts about ice shelves.

  • Ice shelves are extensions of land-based ice sheets that float on the sea. They can be several hundred meters thick and are found mainly in bays around Antarctica, with some in the Arctic. Antarctica’s biggest, the Ross Ice Shelf, is the size of France.
  • Scientists worry that that the collapse of ice shelves could prompt glaciers inland to start sliding faster toward the sea, raising sea levels. Antarctica holds enough fresh water to raise sea levels by 57 meters (187 ft), so even a limited melt would have big consequences.
  • Since 1950, ten ice shelves on the Peninsula, which snakes up toward South America, have contracted or collapsed.
  • The British Antarctic Survey reckons that 25,000 sq km (10,000 sq mile) of ice shelves have been lost in total — an area the size of Macedonia, Rwanda or the U.S. state of Vermont.
  • Ice shelves that have broken up since 1950 are the Larsen A, Larsen B and Larsen C, Prince Gustav, Muller, Jones, Wordie, George VI north, George VI south and the Wilkins.
  • Among the most dramatic collapses was that of the Larsen A within a few weeks in 1995, when satellite images abruptly showed the bay dotted with icebergs. The Larsen B also abruptly collapsed in 2002.

(Editing by Andrew Roche) – copyright the author or the news agency.

Posted in Antarctica, Climate Change, Larsen A | Tagged: , , , , | 28 Comments »

A Fast-Warming World

Posted by feww on March 26, 2008

Antarctic Ice Shelf Collapse Highlights a Fast-Warming World

Satellite images from the National Snow and Ice Data Center at the University of Colorado at Boulder reveal a massive ice shelf the size of Connecticut (13,680 square kilometer, or 5,282 square mile) collapsing because of rapid climate change in a fast-warming region of Antarctica.

Satellite images show the Wilkins Ice Shelf breaking up. The large image recorded March 6; right, from top to bottom, February 28, February 29, and March 8. Credit: National Snow and Ice Data Center/NASA


The Wilkins Ice Shelf broke into a sky-blue pattern of exposed deep glacial ice. This true-color image of the Wilkins Ice Shelf was taken by MODIS on March 6, 2008. Credit: National Snow and Ice Data Center

The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwest Antarctic Peninsula, about 1,000 miles south of South America. In the past 50 years, the western Antarctic Peninsula has experienced the biggest temperature increase on Earth, rising by 0.5 degree Celsius (0.9 degree Fahrenheit) per decade. NSIDC Lead Scientist Ted Scambos, who first spotted the disintegration in March, said, “We believe the Wilkins has been in place for at least a few hundred years. But warm air and exposure to ocean waves are causing a break-up.”


An enhanced-color image of the Wilkins Ice Shelf in Antarctica on March 8, 2008. Narrow iceberg blocks (150 meters wide, or 492 feet) crumbled into house-sized chunks. Credit: Left, National Snow and Ice Data Center; right, National Snow and Ice Data Center/courtesy Cheng-Chien Liu, National Cheng Kung University (NCKU), Taiwan and Taiwan’s National Space Organization (NSPO); processed at Earth Dynamic System Research Center at NCKU, Taiwan.

Collapsing Ice Shelves

Disintegration of Mega-iceberg A53a, South Atlantic

In April 2005, the A53a iceberg broke off the Larsen Ice Shelf on the Antarctic Peninsula drifting north where it encountered warmer temperatures and, nearly three years later, began to disintegrate. Image Credit: NASA Earth Observatory

The mega-iceberg A53a (upper image) measured about 50 kilometers by 22 kilometers, seven times the area of Manhattan Island, in mid-January 2008 when astronauts took the photographs for this mosaic. Ted Scambos, glaciologist and Lead Scientist at the National Snow and Ice Data Center [he stitched together three detailed images of mega-iceberg A53aby to make this image,] said, “This is an iceberg worth watching, because, being water-saturated, it may well show a sudden, crumbling, disintegration, spreading fine blue micro-icebergs over the ocean surface.”

The lower image shows A53a in the process of breaking off from the Larsen Ice Shelf in late 2004; the future ice berg is indicated by a dashed line in the image. The wider view of the ice shelf is based on the MODIS Mosaic of Antarctica image map. Some features acquired during the iceberg’s calving have been maintained in the years since.

Icebergs of the southern Atlantic Ocean contain rock material from Antarctica, eroded by the moving ice, and also wind-borne dust from deserts in Africa, South America, and Australia. The finest powdery rock material acts as nutrients for sea organisms. As the sediment-laden icebergs melt, they enrich the surrounding seawater with minerals. The area of enrichment is significantly larger when a mega-iceberg disintegrates into many small pieces. Caption [slightly edited] by M. Justin Wilkinson, NASA-JSC.

Larsen B

The Wilkins is one of a string of ice shelves that have collapsed in the West Antarctic Peninsula in the past thirty years. The Larsen B became the most well-known of these, disappearing in just over thirty days in 2002. The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones Ice Shelf collapses also underscore the unprecedented warming in this region of Antarctica.

Mapping the new ice front line towards Cape Foyn: Edge parallel crevasses indicate future calving. Photo courtesy of S. Tojeiro, Fuerza Aerea Argentina, 13 March 2002


View from east to west nunataks Grey, Bruce, and Bull. Photo courtesy of Pedro Skvarca, Instituto Antártico Argentino, 13 March 2002.

Additional images taken from the space by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth.

Posted in Antarctica, Climate Change, Ice Shelf, Satellite image, Warming World, Wilkins | 4 Comments »

More Eco-Terrorism in Antarctica

Posted by feww on November 25, 2007

The critters who commit acts of eco-terrorism (the tourists and the tourism industry) need urgent rehabilitation. And if that fails, they should be put behind bars for the rest of their wretched lives to protect the environment.


“BUENOS AIRES, Nov 23 (IPS) – The second accident this year involving a cruiseliner in the Antarctic is alarming the countries that protect and conserve the frozen continent, which are persisting in their demands for penalties in cases of disasters that cause pollution.”

“Mariano Mémoli, the head of the National Antarctic Directorate at the Argentine Foreign Ministry, told IPS “we are extremely concerned by the frequency of these accidents, but the other countries, which are also alarmed, are taking their time about signing laws to defend the environment.”

“[T]he M/S Explorer, a tourist cruise ship, collided with an iceberg close to the South Shetland Islands, north of the Antarctic Peninsula, shortly after five a.m. on Friday. The 154 people on board, passengers and crew, were taken off in lifeboats and inflatable dinghies, and the damaged ship was left listing at an angle of 45º.”

“… The liner was carrying 185 tons of fuel, and the first assessments agreed that towing it would be risky and costly.” (!)

“Mémoli said that the diesel oil carried by the cruiser is a light fuel, most of which will evaporate, but the residue is highly toxic and soluble in water. “This is an area of high biological value, with penguins, seals, elephant seals, and a range of fish and bird species,” he said.”

“The ship, 73 metres in length and with a beam of 14 metres, flies the Liberian flag. It was built in Finland and is operated by GAP Adventures, a Canadian tourist company.”

“Most of the passengers, who paid an average 8,000 dollars for the cruise, were from the UK, the Netherlands, the U.S. and Australia.” Read more …

See also previous entry and debate: Eco Tourism?

Posted in Antarctica, eco-terrorism, environment, oil pollution | 3 Comments »