King crabs invade Antarctica

By Eric Niiler 

Sven Thatje has been predicting an invasion of deep-water crabs into shallow Antarctic waters for the past several years.

Courtesy of Richard B. Aronson / Florida Tech - A crab in the Bellingshausen Sea.

But the biologist and his colleagues got their first look at the march of the seafloor predators while riding on an icebreaker across frozen Antarctic seas this winter.

The ship towed a robot sub carrying a small digital camera that filmed the seafloor below. It caught images of bright red king crabs up to 10 inches long, moving into an undersea habitat of creatures that haven’t seen sharp teeth or claws for the past 40 million years.

“There were hundreds,” Thatje said in an interview on board the Swedish icebreaker Oden, which docked at the main U.S. base in Antarctica, McMurdo Station, after a two-month research cruise. “Along the western Antarctica peninsula, we have found large populations over 30 miles. It was quite impressive.”

Thatje, an evolutionary biologist at the University of Southampton in England and chief scientist on the cruise, is part of a U.S.-Swedish team of marine researchers who are trying to figure out where, when and how fast this invasion is occurring. King crabs, of which there are 13 species, live in the deep waters off Alaska and Russia and across the Southern Ocean in the waters off New Zealand, Chile and Argentina. But here in Antarctica, crabs haven’t been able to survive because, until now, it’s been too cold. As a result, many bottom-dwelling creatures such as mussels, brittle stars and sea urchins have not developed any defenses against the crabs.

What’s happened is that the waters around the Antarctic peninsula have begun to get warmer. The air temperature has jumped almost 11 degrees Fahrenheit since the 1950s, and the average ocean temperature has increased by one degree over the same period. That slight change in water temperature has lowered a physiological barrier that had previously kept the crabs in check, Thatje said.

When the water is too cold — as it has been along the shallow waters of the Antarctic continental shelf — crabs can’t remove magnesium from their blood. Magnesium is a common mineral in seawater, and if they can’t get rid of it, it causes a narcotic effect that stops them from moving enough to survive.

Some scientists say the magnesium barrier may soon fall, as global climate change continues to affect wildlife at the polar regions.

The lack of clawed, beaked or toothed predators has led to a thick seafloor canopy of sorts, much like a submarine jungle comprising flowery feather stars, tube worms and squirming sea spiders along with clams and mussels.

As they sift through more than 120,000 digital images from their expedition, Thatje and other researchers are looking for evidence that crabs are preying on these creatures.

“The Antarctic shelf communities are quite unique,” Thatje said. “This is the result of tens of millions of years of evolution in isolation.”

The crab research team is analyzing the images of the seafloor, looking for clues into whether the crabs will invade and then leave or permanently colonize the shallow areas. Will their presence destroy the existing community or simply alter it? Previous cruises had spotted only one or two crabs, but now scientists are seeing entire populations, according to Richard Aronson, biology professor at the Florida Institute of Technology and co-investigator on the project, along with James McClintock of the University of Alabama at Birmingham.

The crabs are moving from the deep ocean, up the continental slope to the shallower shelf areas. Unlike most areas of the world, the shallower waters on the Antarctic continental shelf are actually slightly colder than the deeper waters of the Southern Ocean. That’s because of a clockwise current of water called the Antarctic circumpolar current.

That flow of cold water keeps Antarctic marine life — especially the bottom-dwelling creatures — isolated. There are no sharks, rays or fish with bony jaws, for example, in Antarctica.

“If you look at the warming trends on the peninsula, you would expect that the crabs would come back in 40 or 50 years,” Aronson said from his office in Melbourne, Fla. “But, boom, they’re already here.”

Not all experts agree that the crabs are destined to wreak havoc on the sea bottom. David Clarke, a marine ecologist at the British Antarctic Survey, said that the seawater temperature changes may be occurring on the surface of the ocean but that they’re too small to affect animals living on the bottom.

Clarke studies colonial animals in Antarctica, such as sponges and corals, and how they fit into the ecosystem. He said not enough is known about existing crab populations — where they live and how long they have been there — to declare that climate change is causing an invasion.

At the same time, he agrees with the Swedish and U.S. researchers that there are rapid changes underway in Antarctica, especially on the Western Antarctic peninsula, a thumb of land that juts northward to the bottom of South America. There’s less sea ice, for example, on the waters of the peninsula. That is causing problems for the penguins and seals that depend on sea ice for food and shelter.

“Yes, there is some cause for concern in that the rate of [environmental] change is greater than has been the case in recent millions of years,” Clarke said. “Obviously, for animals to tolerate or adapt to things in a very short period of time is going to be tricky.”

Japan quake shifts Antarctic glacier

March 15, 2011 by Anil Ananthaswamy

The major earthquake that hit Japan on Friday caused a massive ice stream in Antarctica to momentarily speed up.

As the surface seismic waves generated by the quake travelled around the world, they appear to have given the Whillans ice stream in West Antarctica a nudge, causing it to shift by about half a metre.

The movement was picked up by Jake Walter of the University of California, Santa Cruz, and his colleagues, who monitor the glacier remotely from California. They say the event is an "interesting insight", but are not suggesting it will destabilise the West Antarctic Ice Sheet in any significant way.

The Whillans ice stream drains ice from the West Antarctic Ice Sheet into the Ross Ice Shelf. Since 2007, Walter and colleagues have been using GPS field stations on the ice sheet to monitor its movements. They have shown that the ice stream speeds up twice a day in slip events which last about 30 minutes.

The glacier normally creeps along at an average speed of about 1 metre per day. But during a slip event, it slides almost half a metre in one go. The sudden slips are related to the tides, and are strong enough to generate seismic waves that are recorded by stations at the South Pole and the Antarctic Dry Valleys (Journal of Geophysical Research, DOI: 10.1029/2010JF001754).

 

Slipping glacier

Now it looks like the magnitude 9.0 earthquake that shook Japan last Friday caused the glacier to slip in a similar way.

When Walter and his colleagues were analysing GPS data from the ice stream on Monday, they noticed that one slip event had happened earlier than expected. Further analysis revealed that it happened exactly when surface seismic waves generated by the Japanese earthquake would have hit Antarctica.

Large earthquakes are known to create seismic waves which can circle the planet several times before dying down.

"The Chile earthquake from last year also had a similar effect" on the Whillans ice stream, Walter told New Scientist. "It's an interesting insight into how large earthquakes might affect glacier motion."

Walter and colleagues now want to examine data from other large earthquakes to see if any others are linked to slip events of the Whillans ice stream.

In the North Atlantic, Oceanic Currents Play a Greater Role in the Absorption of Carbon Than Previously Thought

 

ScienceDaily (Mar. 9, 2011) — The ocean traps carbon through two principal mechanisms: a biological pump and a physical pump linked to oceanic currents. A team of researchers from CNRS, IRD, the Muséum National d'Histoire Naturelle, UPMC and UBO (1) have managed to quantify the role of these two pumps in an area of the North Atlantic. Contrary to expectations, the physical pump in this region could be nearly 100 times more powerful on average than the biological pump. By pulling down masses of water cooled and enriched with carbon, ocean circulation thus plays a crucial role in deep carbon sequestration in the North Atlantic.

---

These results are published in the Journal of Geophysical Research.

The ocean traps around 30% of the carbon dioxide emitted into the atmosphere through human activity and represents, with the terrestrial biosphere, the main carbon sink. Much research has been devoted to understanding the natural mechanisms that regulate this sink. On the one hand, there is the biological pump: the carbon dioxide dissolved in the water is firstly used for the photosynthesis of phytoplankton, microscopic organisms that proliferate in the upper layer of the ocean. The food chain then takes over: the phytoplankton is eaten by zooplankton, itself consumed by larger organisms, and so on. Cast into the depths in the form of organic waste, some of this carbon ends its cycle in sediments at the bottom of the oceans. This biological pump is particularly effective in the North Atlantic, where a spectacular bloom of phytoplankton occurs every year. On the other hand, there is the physical pump which, through oceanic circulation, pulls down surface waters containing dissolved carbon dioxide towards deeper layers, thereby isolating the gas from exchanges with the atmosphere.

On the basis of data collected in a specific region of the North Atlantic during the POMME (2) campaigns, the researchers were able to implement high-resolution numerical simulations. They thus carried out the first precise carbon absorption budget of the physical and biological pumps. They succeeded, for the first time, in quantifying the respective proportions of each of the two mechanisms. Surprisingly, their results suggest that in this region of the North Atlantic the biological pump would only absorb a minute proportion of carbon, around one hundredth. The carbon would thus be trapped mainly by the physical pump, which is almost one hundred times more efficient. At this precise location, oceanic circulation pulls down the carbon, in dissolved organic and inorganic form, to depths of between 200 and 400 meters, together with the water masses formed at the surface.

The key role of the physical pump in the North Atlantic had never been quantified before. Its importance raises numerous questions: how long does the carbon transported by the physical pump remain trapped at depth before being driven back to the surface by the reverse mechanism? Is this proportion between the biological pump and the physical pump observed in other oceanic regions of the planet? And, last but not least, how will this mechanism evolve with climate change, which affects both the physical mechanism and the biological mechanism?

*Notes* (1) The laboratories concerned are: the Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN, UPMC/CNRS/MNHN/IRD) and the Laboratoire des Sciences de l'Environnement Marin (LEMAR, CNRS/IRD/UBO).

(2) The POMME program (Multidisciplinary Meso-Scale Ocean Program) lasted from August 2000 to October 2001. In one year, four oceanographic campaigns were conducted in a specific area of the North Atlantic.

More than one hundred researchers and engineers were involved in this novel program, supported by several French institutions (CNRS, SHOM, Ifremer, Météo-France).

---

Journal Reference:

1. P. Karleskind, M. Lévy, L. Memery. Subduction of carbon, nitrogen, and oxygen in the northeast Atlantic. Journal of Geophysical Research, 2011; 116 (C2) DOI: 10.1029/2010JC006446

Ice Loss Accelerates in Greenland, Antarctica, NASA Study Finds

By Alex Morales - Mar 9, 2011

Greenland and Antarctica’s ice sheets are shrinking more quickly, suggesting United Nations projections for sea-level rise are too conservative, a U.S. National Aeronautics and Space Administration-funded study said. 

From 1992 to 2009, the two regions lost on average 36.3 billion tons more ice every year than the previous year, scientists led by Eric Rignot at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a study in the Geophysical Research Letters journal. The researchers said they linked two independent sets of measurements to validate them. 

Continuing the trend may raise oceans 15 centimeters (6 inches) from 2010 to 2050, and by 56 centimeters by 2100, the study said. That’s more than what was factored into the 2007 projection by the UN’s Intergovernmental Panel on Climate Change for seas to rise 18 to 59 centimeters by 2100. 

“If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations,” Rignot said in a statement e-mailed late yesterday by NASA. “Our study helps reduce uncertainties.” 

The UN prediction also includes the expansion of water with warmer temperatures and the melting of mountain glaciers and smaller ice caps. 

The researchers said their 2050 forecast has a margin of error of 2 centimeters. Melting from mountain glaciers and smaller ice caps would add 8 centimeters to the sea level increase. The expansion of water as temperatures rise would add 9 centimeters, the researchers said. 

They warned their 2100 figure can’t be considered a projection because of “considerable uncertainty in future acceleration of ice sheet mass loss.” 

‘Surprising’ Acceleration 

The IPCC in 2007 said Greenland and Antarctica contributed a combined 0.42 millimeters a year to sea level rise from 1993 through 2003. That’s just over half the 0.77-millimeter contribution from mountain glaciers and smaller ice caps, and a quarter of the 1.6-millimeter rise as a result of water expanding with warmer temperatures. 

The North Atlantic island and southern continent now contribute more than mountain glaciers and ice caps, according to the NASA study. The researchers cited another paper that put the ice loss of the glaciers and ice caps at 402 billion tons in 2006, compared with the 475 billion tons from Greenland and Antarctica in the same year -- equivalent to 1.3 millimeters of sea level rise. The acceleration in ice loss is three times greater than for mountain glaciers, they wrote. 

“That ice sheets will dominate future sea level rise is not surprising -- they hold a lot more ice mass than mountain glaciers,” said Rignot, also a researcher at the University of California, Irvine. “What is surprising is this increased contribution by the ice sheets is already happening.” 

Utrecht University in the Netherlands and the National Center for Atmospheric Research in Boulder, Colorado, also contributed to the research. The scientists correlated different sets of satellite, radar and climate modeling data to produce the study.

Crabs are invading the shallow waters of the Southern Ocean

Mar 3rd 2011 | palmer, Antarctica | 

ANTARCTICA is a peculiar place. For instance, unlike those in most parts of the planet, the ocean depths around it are warmer, at 5ºC or so, than the shallows near the coast. Here, the temperature hovers around 0ºC and can drop to -2ºC. As a consequence, the animals of the Antarctic continental shelf have been free for millions of years from the attentions of predators, such as crabs and sharks, that cannot cope with the cold. The result is an unusual bunch of sea lilies, brittle stars, giant ribbon worms and mollusks that are armored only with thin, soft shells. 

But not, perhaps, for much longer—for crabs are on the march. In the past few years several groups of researchers have spotted king crabs on the continental slope of Antarctica. This slope, which connects the deep ocean with the continental shelf, and whose waters have an average temperature of between 1ºC and 5ºC, is a marginal habitat for king crabs. They die when the temperature drops below 1ºC because they are then unable to process magnesium ions. In small quantities, these ions are needed for energy metabolism. Too many, though, act as a narcotic that eventually kills the animal. Worryingly for sea-lily lovers, the latest research suggests the crabs may be creeping up the slope.

The expedition which made this discovery ended in January. On it, Sven Thatje of Britain’s National Oceanography Centre and his colleagues found hundreds of king crabs—beasts that grow to up to 20cm across, excluding their spindly legs—in waters that had been crab-free on the previous survey, in 2007. They did so by towing a submersible called SeaBED, which belongs to the Woods Hole Oceanographic Institution, in Massachusetts, along a 30-nautical-mile transect of Marguerite Bay, off the west coast of the Antarctic peninsula.

 

As SeaBED cruised over its eponymous target, its cameras took pictures every three seconds and its sensors measured the temperature, salinity and depth of the water. The result is 130,000 images showing hundreds of king crabs, together with details of their immediate environments. All of the crabs were still on the continental slope, but some of them were in shallower water than any seen in 2007. The question, yet to be answered, is whether that was a result of the vagaries of sampling, or because local waters are warming up.

Warming there has certainly been. Since the 1950s, when records began, the average temperature of the ocean to the west of the Antarctic peninsula has gone up by 1ºC. That has expanded the region in which king crabs might live. How much longer it will be before they invade the rich uplands of the continental shelf is hard to say. But, like the monsters in a bad sci-fi film, they are coming.

Arctic blooms occurring earlier: phytoplankton peak arising 50 days early, with unknown impacts on marine food chain and carbon cycling.

 

ScienceDaily (Mar. 3, 2011) — Phytoplankton peak arising up to 50 days early, with unknown impacts on marine food chain and carbon cycling

---

Warming temperatures and melting ice in the Arctic may be behind a progressively earlier bloom of a crucial annual marine event, and the shift could hold consequences for the entire food chain and carbon cycling in the region.

  Significant trends toward earlier phytoplankton blooms (blue) were detected in about 11 percent of the area of the Arctic Ocean closest to the North Pole, delayed blooms (red) were evident to the south. (Credit: Scripps Institution of Oceanography, UC San Diego)

 

Scientists at Scripps Institution of Oceanography at UC San Diego, along with colleagues in Portugal and Mexico, plotted the yearly spring bloom of phytoplankton -- tiny plants at the base of the ocean food chain -- in the Arctic Ocean and found the peak timing of the event has been progressing earlier each year for more than a decade. The researchers analyzed satellite data depicting ocean color and phytoplankton production to determine that the spring bloom has come up to 50 days earlier in some areas in that time span.

The earlier Arctic blooms have roughly occurred in areas where ice concentrations have dwindled and created gaps that make early blooms possible, say the researchers, who publish their findings in the March 9 edition of the journal Global Change Biology.

During the one- to two-week spring bloom, which occurs in warm as well as cold regions, a major influx of new organic carbon enters the marine ecosystem through a massive peak in phytoplankton photosynthesis, which converts carbon dioxide into organic matter as part of the global carbon cycle. Phytoplankton blooms stimulate production of zooplankton, microscopic marine animals, which become a food source for fish.

Mati Kahru, lead author of the study and a research oceanographer in the Integrative Oceanography Division at Scripps, said it's not clear if the consumers of phytoplankton are able to match the earlier blooms and avoid disruptions of their critical life-cycle stages such as egg hatching and larvae development.

"The spring bloom provides a major source of food for zooplankton, fish and bottom-dwelling animals," he said. "The advancement of the bloom time may have consequences for the Arctic ecosystem."

Such a match or mismatch in timing could explain much of the annual variability of fish stocks in the region. "The trend towards earlier phytoplankton blooms can expand into other areas of the Arctic Ocean and impact the whole food chain," say the authors, who used satellite data from 1997-2010 to create their bloom maps. The NASA Ocean Biology and Biogeochemistry Program and the National Science Foundation provided financial support for the research. The satellite data were provided by the NASA Ocean Biology Processing Group, ESA GlobColour group, the National Snow and Ice Data Center and the Japan Aerospace Exploration Agency.

Kahru's coauthors include Greg Mitchell, a Scripps Oceanography research biologist, Vanda Brotas of the University of Lisbon in Portugal and Marlenne Manzano-Sarabia of Universidad Autónoma de Sinaloa in Mexico.

---

Journal Reference:

1. M. Kahru, V. Brotas, M. Manzano-Sarabia, B. G. Mitchell. Are phytoplankton blooms occurring earlier in the Arctic? Global Change Biology, 2010; DOI: 10.1111/j.1365-2486.2010.02312.x

Some Antarctic ice forms from the bottom up

 

Ice melt shows through at a cliff face at Landsend on the coast of Cape Denison in Antarctica December 14, 2009.

Credit: Reuters/Pauline Askin

By Alister Doyle, Environment Correspondent

OSLO (Reuters) - Some of Antarctica's ice sheet is formed by water re-freezing from below not just by snow falling on top as was traditionally thought, findings showed on Thursday that will help scientists project effects of climate change.

Experts are seeking to understand the frozen continent since even a small thaw could swamp low-lying coastal areas and cities. Antarctica contains enough ice to raise world sea levels by about 57 meters (187 ft) if it ever all melted.

A six-nation study of the jagged mountain range as high as the Alps that is buried under ice in East Antarctica found that almost a quarter of the ice sheet in the area was formed by a thaw and re-freeze of water from underneath.

Deep below the surface, ice flowing into narrow, submerged valleys often melted because of high pressure and heat from the earth below and re-froze when it was forced up again.

The findings, published in the journal Science, confound a traditional view that ice sheets are almost solely formed by snow that lands on top, gets compressed into ice and flows slowly toward the oceans because of gravity.

"We usually think of ice sheets like cakes -- one layer at a time added from the top. This is like someone injected a layer of frosting at the bottom -- a really thick layer," Robin Bell, lead author at Columbia University in New York, said in a statement.

DOME

The scientists said that about 24 percent of the ice in an area around Dome A, a 13,800 feet high plateau the size of California that forms the top of East Antarctica, was formed by re-frozen ice.

"In some places up to half the ice thickness has been added from below," they wrote of ice above the invisible Gamburtsev Mountain range.

The finding could help understand flows of Antarctic and Greenland ice sheets, and possible responses to global warming.

The British Antarctic Survey (BAS), which took part, said it gave "new understanding about ice sheet growth and movement that is essential for predicting how the ice sheet may change as the Earth's climate warms."

Radars spotted unexpected bulges deep in the ice -- one was 1 km (0.6 mile) high from the bottom of the ice sheet. "We almost thought the equipment was broken," co-author Tom Jordan of BAS told Reuters.

The U.N. panel of climate scientists projected in a 2007 report that world sea levels may rise by 18-59 cm (7-24 inches) in the 21st century, or by more if a thaw of Greenland or Antarctica picks up.

The thaw and re-freeze might also affect chances of finding unknown life in sub-glacial lakes in Antarctica such as Vostok where Russian scientists have been drilling. These lakes may have been isolated for a shorter time than previously believed.

Antarctica's ice sheet formed about 32 million years ago but Jordan said that experts now believed the oldest ice was only 1.4 million years old.