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Antarctic Science News - archive from 2010
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Bottom of Lake Vostok mapped
1 December 2010
Russian polar explorers and scientists have mapped the bottom of subglacial Lake Vostok. Information for mapping was obtained by means of complex seismic and radar investigations. Lake Vostok is the largest subglacial Antarctic lake known to date. The lake's coastline is 1030 kilometers long, and its water surface area is 15.5 thousand square kilometers. For mapping the lake's bottom, Russian researchers have developed unique techniques, including seismic sounding that required exploding 5-6 lines of detonating cord.
See further details at Russia-InfoCentre.
Feather of the Penguin
12 November 2010
Penguins are highly adapted for their cold, aquatic environment. Changes in their wings and feathers have allowed rapid swimming and protection from the near-freezing water. In This Week in Science, Clarke et al. describe an early penguin, dating to about 35 million years ago, that includes well-preserved feathers. The melanosomes in the feathers, which influence their strength, as well as their colour, are like those of many other aquatic birds and unlike those of present-day penguins, even though the morphology of the wings and feathers had already been modified. Thus, in penguins, the shape and form of the feather evolved before microstructural changes occurred. The melanosome arrangement also suggests that the penguin was mostly grey-brown.
Pine Island Losses
10 November 2010
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Image by Jesse Allen / NASA / |
Mass loss from the Antarctic ice sheet is responsible for much of the observed rise in global sea level. No part of the Antarctic ice sheet is losing mass more quickly than the Pine Island Glacier, whose flow velocity has nearly doubled since the mid-1970s, although it has been unclear exactly how much mass it is losing and which factors are most responsible. Joughin et al. have developed a basin-scale glaciological model to examine the sensitivity of the Pine Island Glacier to various environmental forcings. They find that the factor most responsible for mass loss by the glacier is melting due to exposure of the ice shelf to warm ocean currents, which causes ice shelf thinning, retreat of the grounding line, and a resulting increase in the speed of ice stream flow to the sea. Their model indicates that mass loss there may continue throughout the 21st century at rates similar to, or even slightly greater than, that of the present. They suggest that the rise in sea level by the year 2100 due purely to mass loss by Pine Island Glacier will probably lie between 1.1 and 1.8 cm, perhaps inching up to 2.7 cm — a large increase but still substantially less than the theoretical maximum of between 11 and 39 cm. |
Read the full article in Geophysical Research Letters, Vol. 37, L20502, 5 pp., 2010
Glacial Silicic Acid Concentrations in the Southern Ocean
29 October 2010
In research published recently in Science by Michael Ellwood, Martin Wille and William Maher, reconstruction of nutrient concentrations in the deep Southern Ocean has produced conflicting results. The cadmium/calcium (Cd/Ca) dataset suggests little change in nutrient concentrations during the last glacial period, whereas the carbon isotope (
13C) dataset suggests nutrient concentrations were higher. The researchers determined the silicon isotope (30Si) composition of sponge spicules from the Atlantic and Pacific sectors of the Southern Ocean and found higher silicic acid concentrations in the Pacific sector during the last glacial period. In their paper, they propose that this increase results from changes in the stoichiometric uptake of silicic acid relative to nitrate and phosphate by diatoms, thus facilitating a redistribution of nutrients across the Pacific and Southern Ocean. Their results are consistent with the global Cd/Ca dataset and support the silicic acid leakage hypothesis.
Read the full report in Science
Behind the Eco-Label - a Debate Over Antarctic Toothfish
27 September 2010
The controversial case of the Antarctic toothfish has raised questions about the gold standard for environmentally friendly fishing.
In grocery stores around the world, discerning consumers can select fish that come with a distinctive blue label and a checkmark. It's the most common eco-label for seafood, offering guilt-free eating in exchange for a premium price. This stamp of approval from the Marine Stewardship Council (MSC), a rapidly growing non-profit organisation based in London, means that the fishing operation doesn't catch so many fish that it jeopardizes the stock. Moreover, the fishing techniques should minimize collateral damage to the ecosystem, such as accidentally catching sea birds or turtles.
But how well the sticker delivers on its promise is up for debate. Critics, both academic scientists and those with environmental groups, say MSC dispenses its labels too liberally, when there are not enough data for a definitive evaluation. They also say the process of certification can be too subjective. The result, they say, is that fisheries are certified when they aren't clearly sustainable.
In Ground-Based Astronomy's Final Frontier, China Aims for New Heights
8 September 2010
No place on Earth rivals the Antarctic Plateau for stargazing. The air is thin and bone-dry; dust is minimal. As observatories go, the higher the better — and at 4093 metres above sea level, it doesn't get any higher on the East Antarctic icecap than Dome A. Last year, Chinese researchers opened Kunlun Station near Dome A. Now they intend to find out if a superior vantage point translates into superior astronomy. At a workshop last month, astronomers unveiled plans to build two major telescopes at Dome A during the Chinese government's next 5-year plan, to start in 2011. The 2.5-metre Kunlun Dark Universe Telescope, or KDUST, would survey the optical and near-infrared bands for planets beyond our solar system and plumb the mysteries of dark matter and dark energy. However, "one instrument would be lonely," says astronomer Yang Ji, director of Nanjing's Purple Mountain Observatory, which is developing a companion: a 5-metre terahertz (THz) telescope to observe 200- to 350-micrometer wavelengths. This "under-explored frequency window" is acutely sensitive to gas clouds — ideal for probing, for example, star and planet formation, says Qizhou Zhang, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and a member of the group that initiated the THz telescope project.
The two telescopes would be a major expansion of China's formidable Antarctic buildup. During the 2007–08 International Polar Year, China erected Kunlun Station, teamed with the United States and others to study the Gamburtsev Mountains — the origin of the East Antarctic ice sheet — and with Australia began testing observing conditions at Dome A. To pave the way for expansion, China last year built an ice runway at Kunlun; until now, all materials and people have been brought in by arduous traverses.
Read the full Science article.
Antarctica's Adolescence
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Image credit: |
By Brooks Hanson. Antarctica, particularly East Antarctica, harbours much of the world's ice. Thus, accurate knowledge of its sensitivity to melting from global warming is critical for assessing likely sea-level rise in the years ahead. To this end, two recent studies examine the region's dynamics during past glacial cycles and the period when it first grew. Lilly et al. use cosmogenic isotopes, which accumulate in exposed bedrock, to show that the height of the East Antarctic ice sheet fluctuated by only about 100 m through at least the last glacial cycle; the best model fit to the data includes a slow decline in height over longer times. Thus, the East Antarctic ice sheet has had a stable height during past glaciations. In exploring its stability during warmer times, Peters et al. show that an incised coastal valley in Egypt records a sudden and rapid change (within 2 million years) in sea level of about 40 m, at the time when global records imply that major ice sheets first grew in Antarctica, about 35 million years ago. Several smaller fluctuations in sea level (of about 10 m) are also recorded. The rapid changes correlate with estimated fluctuations in atmospheric CO2 levels and occurred when levels dropped below about 750 ppm. |
| To read the abstracts or full texts of the articles, see the August 2010 issue (v. 38, no. 8) of Geology Lilly et al., p. 703; Peters et al., p. 723. |
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IceCube Neutrino Observatory Picks Up Cosmic Rays
Next year, scientists will cut the ribbon on IceCube, a neutrino observatory consisting of strings of detectors buried deep in Antarctic ice. But eager researchers have already used the unfinished detector to search for a different type of particle from space, called cosmic rays—mostly energetic protons and helium nuclei of cosmic origin. Both cosmic rays and neutrinos create the same particles—muons—when they collide with matter, and muons are what the observatory is designed to detect. Only neutrinos, however, can travel through Earth. So muons that come from below are from neutrino collisions inside the ice, whereas the vast majority of muons that come from above are created by cosmic ray collisions in Earth's atmosphere. Next month in The Astrophysical Journal Letters, researchers report that they used IceCube to study a longstanding puzzle: whether the distribution of cosmic ray arrivals is uneven across the southern sky, as scientists have previously observed in the northern hemisphere. Indeed, the team found, IceCube detected a disproportionate number of cosmic rays arriving from some parts of the sky. But the reason for this uneven distribution remains unclear.
For a photograph of the observatory, see the original Science article.
Untangling the Threads
During the last deglaciation, between approximately 18,000 and 10,000 years ago, the atmospheric concentration of CO2 rose from around 180 to more than 260 parts per million. Although several plausible explanations for this increase have been proposed, it has not yet been possible to assign one over the others definitively. Lourantou et al. provide an additional constraint for the competingscenarios: a record of the isotopic composition of the carbon in atmospheric CO2 over the time interval in question. Because different sources of atmospheric CO2 have distinct carbon isotopiccompositions, the authors could determine where in the carbon system the CO2 was coming from by comparing their data with proxy records related to carbon cycle processes, and also by conducting simulations using carbon cycle box models. They conclude that most of the increase in atmospheric CO2 was caused by Southern Ocean ventilation and upwelling, with additional contributions at various times from a decline in marine productivity and a buildup of terrestrial carbon. More sophisticated Earth system models that incorporate carbon cycle–climate feedbacks could help to disentangle the contributions of the processes involved in the rise.
By H. Jesse Smith in Global Biogeochem. Cycles 24, GB2015 (2010).
Warming the Deep
The coldest ocean waters are located at the bottoms of the major ocean basins, and, because it takes a long time for water to sink from the surface to these regions, they are relatively isolated from the warming trends that are now occurring at shallower depths. However, warming in these deep waters has recently been observed, sooner than anticipated. Masuda et al. in Science performed computer simulations of ocean circulation and found that internal waves are able to transport heat rapidly from the surface waters around Antarctica to the bottom of the North Pacific, which can occur within four decades, rather than the centuries that conventional mechanisms have suggested.
Read the full Science article.
The History of the Antarctic - available to download
Melvyn Bragg discusses the geological and political history of the Antarctic (BBC Radio 4, 'In Our Time'), with Jane Francis, David Walton and Julian Dowdeswell.
Listen to the programme (BBC iPlayer)
Download the programme (Podcast)
Could East Antarctica Be Headed for Big Melt?
New research highlighted in Science (Science 25 June 2010: Vol. 328. no. 5986, pp. 1630) suggests that the world's largest ice sheet may be more vulnerable than once thought to rising CO2 levels and temperatures.
The Orangeburg Scarp, a band of hard, crusty sediment teeming with tiny plankton fossils that runs from Florida to Virginia, marks an ancient shoreline where waves eroded bedrock 3 million years ago. That period, the middle Pliocene, saw carbon dioxide levels and temperatures that many scientists say could recur by 2100. The question is: Could those conditions also result in Pliocene-epoch sea levels within the next 10 to 20 centuries, sea levels that may have been as much as 35 meters higher than they are today? The answer, say climate scientists, may lie 17,000 kilometers away in East Antarctica. The East Antarctic Ice Sheet is the world's largest, a formation up to 4 km thick and 11 million km2 in area that covers three-quarters of the southernmost continent. Its glaciers were thought to sit mostly above sea level, protecting them from the type of ocean-induced losses that are affecting the West Antarctic Ice Sheet. But studies of ancient sea levels that focus on the Orangeburg Scarp and other sites challenge that long-held assumption.
Not everybody believes the records from Orangeburg. But combined with several other new lines of evidence, they support the idea that parts of East Antarctica could indeed be more prone to melting than expected.
For further details, see the full Science article.
Underwater Ridge clue to Antarctic ice loss
The discovery of an underwater ridge in West Antarctica could help explain why there has been an acceleration in the ice flowing from a glacier in the area. Researchers suggest that the base of Pine Island Glacier once sat on the ridge, but recently became detached from the feature. The team made the discovery during surveys that used an unmanned submarine to examine waters under the glacier. The findings have been published in the journal Nature Geoscience and highlighted by the BBC. "We found something very unexpected," said co-author Pierre Dutrieux, from the British Antarctic Survey (BAS), referring to the 400m-high ridge. "Acoustic instruments on the submarine told us that there was a ridge at the bottom of the ocean, sitting transverse to the flow of ice." Dr Dutrieux said that there was also evidence that the base of the glacier was once attached to the ridge. "Some decades ago, the glacier was sitting on this ridge and the friction of the ridge was restraining the flow of the glacier," he explained. "When the glacier became detached from the ridge, the ice flow was able to accelerate significantly." Dr Dutrieux said that the glacier was located in an area where there was intense melting of land ice, which was flowing into the ocean and contributing to sea level rise. Researchers estimate that the accelerating flow of glaciers in West Antarctica is contributing about 10% of the observed rise in the mean global sea level.
For further details, see the full BBC News article.
How Do Polar Marine Ecosystems Respond to Rapid Climate Change?
In a recent article in Science, Oscar Schofield and co-authors discuss how Southern Ocean observations are required in order to study the future of polar ecosystems as climate change progresses. Climate change will alter marine ecosystems; however, the complexity of the food webs, combined with chronic undersampling, constrains efforts to predict their future and to optimally manage and protect marine resources. Sustained observations at the West Antarctic Peninsula show that in this region, rapid environmental change has coincided with shifts in the food web, from its base up to apex predators. New strategies will be required to gain further insight into how the marine climate system has influenced such changes and how it will do so in the future. Robotic networks, satellites, ships, and instruments mounted on animals and ice will collect data needed to improve numerical models that can then be used to make predictions of how the ecosystem will change. The SCAR/SCOR Oceanography Expert Group, co-chaired by one of the co-authors of the article, Mike Meredith, is producing a plan for a Southern Ocean Observing System (SOOS) in consultation and partnership with the science, logistics and other communities.
Read the full Science article.
Southern Ocean store of CO2
Past glacial-interglacial increases in the concentration of atmospheric carbon dioxide (CO2) are thought to arise from the rapid release of CO2 sequestered in the deep sea, primarily via the Southern Ocean. Two recent articles in Science (28 May 2010:Vol. 328. no. 5982) discuss this in terms of radiocarbon evidence from the Atlantic sector of the Southern Ocean that strongly supports this hypothesis (Ventilation of the Deep Southern Ocean and Deglacial CO2 Rise, Skinner et al.). Anderson and Carr (Uncorking the Southern Ocean's Vintage CO2) discuss the scenarios involved. In particular, how CO2 records from ice cores and 14C records from marine archives reveal that the 14C content of atmospheric CO2 declined as CO2 rose during the last deglaciation. This relationship supports hypotheses that attribute the rise in CO2 to the release of 14C-depleted CO2 from a reservoir long isolated from the atmosphere. The deep ocean (below 2000 m) is thought to provide such a reservoir.
Discovery of the Ozone hole: 25th Anniversary
The discovery of the Antarctic ozone hole, as reported in Nature 25 years ago, was one of the most dramatic scientific findings of modern times. To mark the anniversary, Nature presents the original research paper reporting the considerable decline in springtime atmospheric ozone concentration over Antarctica, along with a new Opinion piece from one of the paper's authors, plus a collection of related articles that have advanced our understanding of the stratosphere and the ozone layer, or told the story of the discovery.
Access selected contents here.
An oceanic 'fast-lane' for climate change
Work in Japan and Australia has revealed that a deep-ocean current is carrying frigid water rapidly northward from Antarctica along the edge of the Kerguelen Plateau, a more than 2,200-kilometre-long rise some 3,000 kilometres south-west of Australia.
Yasushi Fukamachi, an ocean scientist at Hokkaido University in Sapporo, Japan, led a team effort to determine the exact nature of the current. The researchers moored over 30 current and temperature recorders across its probable path and left these in place for two years. When they retrieved their instruments, the scientists discovered that the current, which flows at depths well below 3,000 metres, sometimes hit speeds greater than 700 metres per hour, carrying volumes as high as 30 million cubic metres per second. No other deep current in the Southern Hemisphere is known to move that quickly.
The current is formed by cold water sinking in the Ross Sea and off the coast of Adelie Land, on the Australian-facing side of Antarctica. Once in the abyss, the water flows eastward along the coast of Antarctica before hitting the Kerguelen Plateau. Then, just as the Gulf Stream hugs the eastern edge of North America, Coriolis force from Earth's rotation causes the Antarctic water to embrace the plateau's eastern flank. The result is a narrow, and so fast-moving, stream, about 50 kilometres wide.
This is significant because it represents a "fast lane" by which climatic and environmental changes affecting the Southern Ocean can propagate northward, says Alejandro Orsi, a physical oceanographer at Texas A & M University in College Station, who was not involved in the study. Proof that this is already occurring, he adds, can be seen from the fact that the deep waters near the Kerguelen Plateau already show "clear signs" of reduced salinity relating to changes in the rate of melting of Antarctic ice sheets.
Read the full Nature article.
Announcement of POGO Opportunities in Capacity Building
The Partnership for Observation of the Global Oceans (POGO) announces three capacity building programmes. In collaboration with the Scientific Committee on Oceanic Research (SCOR), it announces the POGO-SCOR Visiting Fellowship Programme for 2010, which offers successful candidates the opportunity to visit other oceanographic centres for a period of between 1 and 3 months. POGO also announces a special AMT Visiting Fellowship for on-board training on an Atlantic Meridional Transect (AMT) Cruise, offering the successful candidate the opportunity to participate in the preparation of the cruise at Plymouth Marine Laboratory or at the National Oceanography Centre in Southampton for up to a month prior to the cruise, participation in the cruise itself (12 October-25 November) and up to two months in the same institute after the cruise to participate in the data analysis and processing on completion of the cruise. Priority for both fellowships will be given to applicants in the early stages of career development.
POGO also announces the POGO Visiting Professorship for 2010, which allows for a visit by a distinguished scientist from an advanced oceanographic institute to an institute in a developing country or country with economy in transition, to provide training and mentoring, to develop collaborations and to enhance networking. The duration of visits may range from 2 weeks to 3 months.
Full information for all three schemes, including applications forms and deadlines, can be found on the POGO website.
Rocks available for study from Pensacola Mountains, Antarctica
The US Polar Rock Repository has added many samples over the past year, particularly from the Pensacola Mountains region. We currently have over 18,000 samples at the USPRR available for research (including using destructive techniques), teaching or museum use. Requests are welcome from both the US and international community. In some cases, we have accompanying petrographic thin sections and analytical metadata associated with the samples. The easiest way to search our collection is through the highlighted 'Detailed Search' choice listed on the Polar Rock Repository home page.
Loan requests can be made through the website 'sample bag' feature. If you have a particular area of interest and do not see the samples you need, please contact us (curator@bprc.ohio-state.edu) because we have collections that are not yet cataloged. We also measure magnetic susceptibility on all samples larger than 6cm x 6cm and can provide this data in an Excel file.
Antarctic Science Career Development Bursaries
The Antarctic Science Career Development Bursaries are awards of up to £5000, made annually to support the development of the careers of promising young scientists, working in any field of Antarctic science. The purpose of the award is to broaden the scope of an existing research project, especially for postdoctoral studies, through:
- funding extra field or laboratory work,
- purchasing/contributing towards the cost of a key piece of equipment, or
- funding international collaboration
Applications must be submitted to arrive at the Antarctic Science Office, no later than 2400 GMT on March 31st of each year. Allowance will not be made for late submission from other time zones. Applicants should be at least post-graduate or, preferably, post-doctoral and, if the latter, should be not more than 10 years from the start of their PhD. A condition of acceptance of the Antarctic Science Career Development Bursary is that the recipient must undertake to offer to Antarctic Science a first- or lead-author paper following on from the outcomes of the science activity for which the Bursary was awarded, or from science activity associated with it. Subject to satisfactory review by the usual processes, the paper will be published in Antarctic Science and the author identified as the winner of an Antarctic Science Bursary. In addition the recipient must acknowledge the award in presentations and publications.
For application forms and detailed requirements, please visit the Antarctic Science website.
Australia and Antarctica Linked by Climate
A recent study by Tas Van Ommen and Vin Morgan (Nature Geiscience, DOI: 10.1038/ngeo761) suggests that the 40-year drought that has blighted Australia may be linked to heavy snowfall over Antarctica. The researchers noticed the link after nearly 30 years of studying Antarctic ice cores extracted from Law Dome, an ice field near Cape Poinsett, which lies almost exactly south of the southwestern tip of Australia. There they found evidence that the area had been experiencing abnormally large amounts of snowfall for several decades. They also knew that southwestern Australia had been suffering from severe droughts for approximately the same time.
They compared the 750 year long ice-core records with meteorological records to gauge precipitation patterns in southwestern Australia, as well as atmospheric circulation patterns in the Southern Hemisphere for the past four decades. About 40% of the rainfall variations in southwestern Australia were mirrored by snowfall variations at Law Dome. More intriguing, the Law Dome snowfall patterns seem to have intensified over the past several decades. Indeed, climate models predict such an anomaly when anthropogenic carbon dioxide (CO2) emissions over the last century are factored in. According to the models, higher levels of CO2, coupled with reductions in atmospheric ozone, create an atmospheric circulation pattern in the Southern Ocean that brings drier air to the farming regions of southwestern Australia and heavier snows to Law Dome. But as the models show, by boosting CO2 and cutting ozone, the normal cycles can be disrupted, and that is what seems to be happening now.
Antarctic Glacier Off Its Leash
An unmanned autonomous submarine has discovered a sea-floor ridge that may have been the last hope for stopping the now-accelerating retreat of the Pine Island Glacier, a crumbling keystone of the West Antarctic Ice Sheet, researchers announced at the fall meeting of the American Geophysical Union.
The Pine Island and adjacent Thwaites glaciers are key to the fate of West Antarctic ice, says glaciologist Richard Alley of Pennsylvania State University, University Park, in an e-mail. And West Antarctica is key to how fast and far sea level will rise in a warming world. "To a policymaker, I suspect that the continuing list of [such] ice-sheet surprises is not reassuring," he writes.
Read the full Science article.
The Southern Ocean and uptake of anthropogenic CO2
The Southern Ocean accounts for only about 6% of the world's ocean area, although it is estimated that it absorbs as much as 40% of the CO2 taken in by the seas. However, the Southern Ocean retains only about 9% of the CO2 it absorbs. What happens to the rest of it? Ito et al. were able to pinpoint the wind patterns and currents that distribute ocean CO2 (primarily related to the so called Ekman transport). As the team report, instead of sinking in place, almost all of the CO2 is carried away from the Antarctic and toward the subtropics - hence the missing CO2 in the Southern Ocean.
Takamitsu Ito said that "the atmosphere overlying the Southern Ocean is undergoing significant climate change". It's possible, he says, that "changing the atmospheric wind pattern in the region could alter the rate at which the Southern Ocean absorbs CO2," possibly reducing the ocean's ability to consume the gas and leading to further global warming.
For further details, see the full article in Nature.
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