Antarctic Science News
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5 March 2014
According to a new study published in Geophysical Research Letters, the Ross Sea, a major, biologically productive Antarctic ecosystem, "clearly will be extensively modified by future climate change" in the coming decades as rising temperatures and changing wind patterns create longer periods of ice-free open water, affecting the life cycles of both predators and prey.
The researchers note that over the last 50 years the distribution and extent of Antarctic sea ice, or ice that floats on the ocean surface, have drastically changed. Among these changes are a documented decrease of sea ice in the Bellingshausen-Amundsen sector, but an increase of sea ice in the Ross Sea sector of Antarctica.
Observations show, they write, that "the duration of ice-free days on the Ross Sea continental shelf has decreased by over two months over the past three decades," which may have had effects on the current balance of biological productivity and the roles of various creatures and microscopic plants in the ocean ecosystem.
But, they also note, "future projections of regional air temperature change, however, suggest that substantial warming will occur in the next century in the Ross Sea sector" while wind speeds are predicted to increase in some areas while decreasing in others. "These changes are expected to reverse the sea-ice trends in the future; however the projected changes in heat content on the continental shelf and ecosystems dynamics that will occur as a result of such changes remain far from certain."
The model, however, indicates that summer sea ice in the Ross Sea could decrease by more than half, or 56 percent, by 2050 and by more than three-quarters, or 78 percent, by 2100. At the same time, the summer mixing of shallow and deep waters in the region as a result of other changes is expected to decrease.
"Regardless of the exact nature of the alterations," the researchers write, "substantial portions of the food web that depend on ice in their life cycles will be negatively impacted, leading to severe ecological disruptions."
5 March 2014
In 1974, newly available satellite observations unveiled the presence of a giant ice-free area, or polynya, within the Antarctic ice pack of the Weddell Sea, which persisted during the two following winters. Subsequent research showed that deep convective overturning had opened a conduit between the surface and the abyssal ocean, and had maintained the polynya through the massive release of heat from the deep sea. Although the polynya has aroused continued interest, the presence of a fresh surface layer has prevented the recurrence of deep convection there since 1976, and it is now largely viewed as a naturally rare event.
In Nature Climate Change, de Lavergne et al present a new analysis of historical observations and model simulations that suggest deep convection in the Weddell Sea was more active in the past, and has been weakened by anthropogenic forcing. The observations show that surface freshening of the southern polar ocean since the 1950s has considerably enhanced the salinity stratification. Meanwhile, among the present generation of global climate models, deep convection is common in the Southern Ocean under pre-industrial conditions, but weakens and ceases under a climate change scenario owing to surface freshening. A decline of open-ocean convection would reduce the production rate of Antarctic Bottom Waters, with important implications for ocean heat and carbon storage, and may have played a role in recent Antarctic climate change.
24 February 2014
New research, published this week in Science, suggests that the largest single contributor to global sea level rise, a glacier of the West Antarctic Ice Sheet, may continue thinning for decades to come.
Geologists from the UK, USA and Germany found that Pine Island Glacier (PIG), which is rapidly accelerating, thinning and retreating, has thinned rapidly before. The team say their findings demonstrate the potential for current ice loss to continue for several decades yet.
Their findings reveal that 8000 years ago the glacier thinned as fast as it has in recent decades, providing an important model for its future behaviour. The glacier is currently experiencing significant acceleration, thinning and retreat that is thought to be caused by 'ocean-driven' melting; an increase in warm ocean water finding its way under the ice shelf.
For more information, read the original report in Science.
19 February 2014
Scientists have demonstrated a new method for counting whales from space. It uses very high-resolution satellite pictures and image-processing software to automatically detect the great mammals at or near the ocean surface.
A test count, reported in the journal PLOS One was conducted on southern right whales in the Golfo Nuevo on the coast of Argentina. The automated system found about 90% of creatures pinpointed in a manual search of the imagery.
This is a huge improvement on previous attempts at space-borne assessment, and could now revolutionise the way whale populations are estimated.
For more information, see the item on the BBC News - Science and Environment website or read the original paper in PLOS One.
19 February 2014
The IceBridge MCoRDS L2 Ice Thickness (IRMCR2) data set contains depth sounder measurements over Greenland and Antarctica taken from the Multichannel Coherent Radar Depth Sounder (MCoRDS). The data set includes measurements for elevation, surface, bottom, and thickness. The data were collected as part of Operation IceBridge funded campaigns, and are stored in Comma Separated Value (CSV) text format with associated KML files, and are available for periodic, ongoing campaigns from 16 October 2009 to the present via FTP.
For more information, visit the National Snow and Ice Data Center (NSIDC) website.
30 January 2014
A number of floating ice shelves in Antarctica are at risk of disappearing entirely in the next 200 years, as global warming reduces their snow cover. Their collapse would enhance the discharge of ice into the oceans and increase the rate at which sea-level rises. A rapid reduction of greenhouse gas emissions could save a number of these ice shelves, researchers at Utrecht University and the British Antarctic Survey say in a new paper published in the Journal of Glaciology.
Back in 1995 and 2002, two floating ice shelves in the north of the Antarctic Peninsula (Larsen A and B) suddenly collapsed – each event occurred in a matter of weeks. Dr Peter Kuipers Munneke, the paper's lead author, said "This was a spectacular event, especially when you imagine the size of these ice shelves, which are several hundreds of metres thick, and have been in place for over 10,000 years."
The team of researchers suspected that the disappearance of the snow layer on top of the ice shelves could be an important precursor for shelf collapse. Their calculations confirm this hypothesis, and show that many more ice shelves could disappear in the next 200 years.
The scientists believed the snow layer plays an important role in regulating the effect of meltwater lakes on the ice shelves. As long as the snow layer is sufficiently thick and cold, all meltwater can sink into the snow and refreeze. But in a warmer climate, the amount of meltwater increases, and the snow layers become thinner. As a result, meltwater can no longer refreeze and forms large lakes on the surface of the ice shelves. The water drains through cracks and faults, causing them to widen until they become so wide and deep that the entire ice shelf disintegrates. After their collapse, ice shelves can no longer provide resistance to the flow of the glaciers previously feeding them. As a result, the glacier flow accelerates significantly, contributing to an increase in sea-level rise.
The researchers performed calculations that show how this process may evolve over the next 200 years, using two different climate scenarios. Dr Kuipers Munnekke said: "If we continue to burn fossil fuels at the current rate, almost all ice shelves in the Antarctic Peninsula will be under threat of collapse in the next 200 years. Only the two largest ones seem to be safe. Even in the much colder eastern part of Antarctica, some ice shelves could disintegrate. If we manage to keep global warming below the European Union target of 2°C, more than half of the ice shelves could be saved, compared to no action taken on emissions reductions."
The study received financial support from the European Union's four-year ice2sea project. Prof David Vaughan said "We've been observing ice-shelf retreat around the Antarctic Peninsula since the early 1990s, but for the first time this model provides a strong basis for the prediction of future changes, which is a major step forward in understanding future sea-level changes."
For more information, read the paper in the Journal of Glaciology:
"Firn air depletion as a precursor of Antarctic ice-shelf Collapse" Peter Kuipers Munneke, Stefan R.M. Ligtenberg, Michiel van den Broeke, David G. Vaughan, Journal of Glaciology, 60 (220), (2014), 10.3189/2014JoG13J183.
23 January 2014
Several glaciers in the Antarctic Peninsula pass between sharp mountain peaks and converge in a single calving front, as seen by Operation IceBridge while returning from a survey of the Ronne Ice Shelf on 1 November 2012. NASA's Operation IceBridge is an airborne science mission to study Earth's polar ice.
Though physically about as distant from Antarctica as you can get, water masses in the North and Tropical Atlantic Ocean significantly influence the effects of climate change on the icy southernmost continent, new research suggests.
Antarctic climate has changed considerably over the past several decades, with the Antarctic Peninsula — located on the West Antarctic Ice Sheet (WAIS) — experiencing more warming than any other region on Earth. Researchers have long recognized that atmospheric and oceanographic conditions, such as wind speed and direction, in the southern Pacific Ocean play an important role in the climate of Antarctica and the distribution of its ice. But Pacific conditions cannot entirely explain all the changes currently occurring in and around Antarctica, particularly during the austral (Southern Hemisphere) winter.
Now, a team of researchers based at New York University has studied more than 30 years of atmospheric data collected from around the world to try to identify other key atmospheric players in Antarctic climate. The team found that water temperatures in the North and Tropical Atlantic Ocean correlate strongly with sea-level pressure in Antarctica's Amundsen Sea, which influences the behaviour of sea ice in the region.
The team next tested whether the correlation between Atlantic and Antarctic water masses represented a true cause-effect relationship, or whether it was just a coincidence. To do so, the researchers used atmospheric models to simulate changes in the Antarctic climate under various global atmospheric and oceanic conditions. To their surprise, they found that directly raising temperatures in the North and Tropical Atlantic in their models did, indeed, have the same effects on wind patterns and ultimately the distribution of sea ice around Antarctica as the historical records showed happened in real life.
This suggests that the Atlantic temperatures and Antarctic sea ice are causally linked, said David Holland, on of the study's authors.
It may seem counterintuitive that ocean temperatures in one hemisphere could have such a large impact on ice distribution in another hemisphere. However, as Holland explained, Atlantic conditions propagate out of the Northern Hemisphere in an atmospheric ripple effect: warm water masses in the Atlantic change atmospheric conditions that eventually turn the gears of the Southern Hemisphere's atmospheric patterns, finally getting sucked down into the region surrounding Antarctica.
Next, the team hopes to better understand what drives the yearly and decadal changes in the North and Tropical Atlantic Ocean that have caused observed changes in Antarctica over the past 30 years. They also want to better understand why ice in Antarctica reacts to climate changedifferently than does ice in the Arctic. Antarctic ice has been redistributed more than it has disappeared in recent years, while Artic ice has experienced more melting.
Xichen Li, David M. Holland, Edwin P. Gerber, Changhyun Yoo. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice. Nature, 2014; 505 (7484): 538 DOI: 10.1038/nature12945
23 January 2014
The persistent wind blowing across the high Antarctic plateau sculpts striking waves and curves in the ice surface, and it seems their signature can be detected in satellite data.
Known as sastrugi, these features have the look of meringue or royal icing. Most are too small to be photographed directly from orbit, but a satellite can discern their presence from the way they scatter a radar signal. Europe's Cryosat spacecraft encountered this issue as it sought to measure changes in the height of the ice. A distinct and very unusual pattern radiating from the South Pole was appearing in its maps. At first, this caused some consternation at the European Space Agency (ESA) because it suggested the mission might have had a fault. It turns out the pattern results from the way the polarised radar signal interacts with the ice surface and near-surface.
Antarctica is dominated by its strong katabatic winds, which run downhill from the interior towards the coast. These winds blow the same way over prolonged periods of time, producing highly directional features in the ice. Sastrugi are one consequence of this, but the preferred alignment affects also the very micro-structure of the snow pack and its crystal orientation. This becomes apparent in the Cryosat maps because the spacecraft acquires its radar data at locations where its orbits cross over. This means the satellite is sensing the directional quality of the ice slightly differently depending on whether it is flying from the north or the south. Now that the scientists understand this effect, they can take account of it in their research, and it will have no impact on the monitoring of elevation changes in the Antarctic. This has become a useful way to understand what is going on underneath the ice sheet, which can rise and fall when great masses of water gather in sub-glacial lakes and then suddenly flood away.
Elevation differences in Antarctica
It might also now be possible to use the radar pattern in an entirely different way. The effects of the wind on the ice sheet, such as sastrugi, eventually become buried, taking with them a record of the prevailing wind behaviour in the Antarctic. By drilling through the ice and studying its layers, scientists have been able to reconstruct this activity stretching back over thousands of years. It is information that has been used to inform models of past atmospheric circulation. Cryosat cannot see as deeply or resolve such fine details, but it is conceivable that the radar artefact could be used to investigate the stability of the wind field over more recent Antarctic history. And being a satellite, Cryosat could observe a wider area of the continent than just the point measurements offered by ice cores.
For further details, see the news item on the ESA website.
13 January 2014
Pine Island Glacier, the largest single contributor to sea-level rise in Antarctica, has started shrinking, say scientists.
The work, published in Nature Climate Change, shows the glacier's retreat may have begun an irreversible process that could see the amount of water it is adding to the ocean increase five-fold.
'At the Pine Island Glacier we have seen that not only is more ice flowing from the glacier into the ocean, but it's also flowing faster across the grounding line - the boundary between the grounded ice and the floating ice. We also can see this boundary is migrating further inland,' says Dr G. Hilmar Gudmundsson from NERC's British Antarctic Survey, a researcher on the project.
The team, which included scientists from the CSC-IT Center for Science in Finland, the Chinese Academy of Sciences and the Universities of Exeter and Bristol, used three computer models as well as field observations to study how the glacier's ice flows and to simulate how this will change over the coming decades.
All the models agreed that the Pine Island Glacier has become unstable, and will continue to retreat for tens of kilometres.
'The Pine Island Glacier shows the biggest changes in this area at the moment, but if it is unstable it may have implications for the entire West Antarctic Ice Sheet,' says Gudmundsson. 'Currently we see around two millimetres of sea level rise a year, and the Pine Island Glacier retreat could contribute an additional 3.5 to 5 millimetres in the next twenty years, so it would lead to a considerable increase from this area alone. But the potential is much larger.'
Pine Island Glacier currently contributes 25 per cent of the total ice loss from West Antarctica. If the entire West Antarctic Ice Sheet was to retreat, it could cause sea level to rise up to five metres.
13 January 2014
Over the last decade, several hundred seals have been equipped with conductivity-temperature-depth sensors in the Southern Ocean for both biological and physical oceanographic studies.
A calibrated collection of seal-derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal-derived data substantially modifies the estimated surface mixed-layer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf.
Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase.
For more information, read the original paper in Geophysical Research Letters.
7 January 2014
A new study published in Science suggests the thinning of Pine Island Glacier in West Antarctica is much more susceptible to climatic and ocean variability than at first thought.
Observations by a team of scientists at British Antarctic Survey, and other institutions, show large fluctuations in the ocean heat in Pine Island Bay. The team discovered that oceanic melting of the ice shelf into which the glacier flows decreased by 50 per cent between 2010 and 2012, and this may have been due to a La Niña weather event.
"Strong sensitivity of Pine Island ice shelf melting to climatic variability" by Pierre Dutrieux, Jan De Rydt, Adrian Jenkins, Paul R. Holland, Ho Kyung Ha, Sang Hoon Lee, Eric Steig, Qinghua Ding, Povl Abrahamsen and Michael Schröder was published initially in Science Express.
7 January 2014
Conservators restoring an Antarctic exploration hut recently made a remarkable discovery. A small box, frozen in a solid block of ice for nearly one hundred years, turned out to be a treasure trove containing 22 unprocessed cellulose nitrate negatives. They're believed to have been snapped by the Ross Sea Party way back in 1915, while they attempted to set up supply depots on the New Zealand side of Antarctica.
The newly discovered negatives were processed and restored in Wellington, New Zealand. Although many of the resulting images are damaged, the Antarctic Heritage Trust has been able to recognise some of the landmarks, in particular around McMurdo Sound.
The negatives were discovered in a corner of a supply depot, originally built by Robert Falcon Scott for his doomed expedition to the South Pole in 1910-1913.
For more information, see the news item on the Imaging Resource website and see the photos on the New Zealand Antarctic Heritage Trust website.
7 January 2014
A species of sea anemone has been found on the underside of Antarctica's ice sheets. They are the only marine animals known to live embedded in the ice, and no one is sure how they survive.
Frank Rack of the University of Nebraska-Lincoln and colleagues made the surprise find when they drilled through the ice for a geological study. They were using a camera attached to a remote-controlled drill to explore the underside of the Ross Ice Shelf when they discovered large numbers of the white anemones, which they christened Edwardsiella andrillae, burrowed inside the ice with only their tentacles dangling into the water.
Marymegan Daly at the Ohio State University analysed samples, but dissecting the creatures revealed little – they looked just like any other anemone. "I would never have guessed that they live embedded in the ice because there is nothing different about their anatomy," she says.
Other species burrow into surfaces by inching their bodies in or digging with their tentacles, but ice should be too hard, says Daly, who thinks the new species may secrete chemicals to dissolve the ice. It is also unclear how they survive without freezing, and how they reproduce.
"We would like to have some genetic information so we can answer some of these questions," Daly says. Unfortunately, as the team were not expecting to find animal life, they only had a preservative with them that could fix the animals' anatomy but destroyed their DNA.
20 December 2013
Scientists say they have discovered compelling evidence that diamonds exist in the icy mountains of Antarctica. The researchers have identified a type of rock in the permanently frozen region that is known to contain the precious stones. However, recovering any Antarctic mineral resources for commercial purposes is currently forbidden.
Diamonds are formed from pure carbon under extreme heat and pressure at depths of about 150km in the Earth's crust. Volcanic eruptions bring the valuable crystals to the surface, usually preserved in another type of bluish rock called kimberlite. The presence of kimberlite has been a clue to significant deposits of diamonds in several parts of the world, including Africa, Siberia and Australia. Now researchers have, for the first time, found evidence of kimberlite in Antarctica. The team found three samples on the slopes of Mount Meredith in the northern Prince Charles Mountains.
16 December 2013
NASA scientists have revealed the inner workings of the ozone hole that forms annually over Antarctica and found that declining chlorine in the stratosphere has not yet caused a recovery of the ozone hole.
More than 20 years after the Montreal Protocol agreement limited human emissions of ozone-depleting substances, satellites have monitored the area of the annual ozone hole and watched it essentially stabilize, ceasing to grow substantially larger. However, two new studies show that signs of recovery are not yet present, and that temperature and winds are still driving any annual changes in ozone hole size.
For further details, see the item on the NASA website.
16 December 2013
Ice loss on West Antarctica affecting mantle flow below
Now that West Antarctica is losing weight - that is, billions of tons of ice per year - its softer mantle rock is being nudged westward by the harder mantle beneath East Antarctica.
The discovery comes from researchers led by The Ohio State University, who have recorded GPS measurements that show West Antarctic bedrock is being pushed sideways at rates up to about twelve millimeters - about half an inch - per year. This movement is important for understanding current ice loss on the continent, and predicting future ice loss. The research group reported results on 12 December at the American Geophysical Union meeting in San Francisco.
Half an inch doesn't sound like a lot, but it's actually quite dramatic compared to other areas of the planet, explained Terry Wilson, Professor of Earth Sciences at Ohio State and Chief Officer of the new SCAR SERCE programme. Prof Wilson leads POLENET, an international collaboration that has planted GPS and seismic sensors all over the West Antarctic Ice Sheet.
She and her team weren't surprised to detect the horizontal motion. After all, they've been using GPS to observe vertical motion on the continent since the 1990s. They were surprised, she said, to find the bedrock moving towards regions of greatest ice loss.
"From computer models, we knew that the bedrock should rebound as the weight of ice on top of it goes away," Wilson said. "But the rock should spread out from the site where the ice used to be. Instead, we see movement toward places where there was the most ice loss."
The seismic sensors explained why. By timing how fast seismic waves pass through the earth under Antarctica, the researchers were able to determine that the mantle regions beneath east and west are very different. West Antarctica contains warmer, softer rock, and East Antarctica has colder, harder rock.
Stephanie Konfal, a research associate with POLENET, pointed out that where the transition is most pronounced, the sideways movement runs perpendicular to the boundary between the two types of mantle. This finding is significant, Konfal said, because we use these crustal motions to understand ice loss.
"We're witnessing expected movements being reversed, so we know we really need computer models that can take lateral changes in mantle properties into account."
Wilson said that such extreme differences in mantle properties are not seen elsewhere on the planet where glacial rebound is occurring. "We figured Antarctica would be different," she said. "We just didn't know how different."
For more details, see the item on the Science Daily website.
16 December 2013
West Antarctica continues to lose ice to the ocean and this loss appears to be accelerating, according to new data from Europe's Cryosat spacecraft. The dedicated polar mission finds the region now to be dumping over 150 cubic km of ice into the sea every year. It equates to a 15% increase in West Antarctica's contribution to global sea level rise. Cryosat was launched in 2010 with a radar specifically designed to measure the shape of ice surfaces. The instrument's novel design, scientists believe, is enabling the European Space Agency (ESA) satellite to observe features beyond the capability of previous missions.
The new study, presented in San Francisco to the American Geophysical Union (AGU) Fall Meeting, confirms the usual suspects to be involved in the increased ice loss. They are Pine Island, Thwaites and Smith Glaciers. These major glaciers and their associated tributaries drain the interior of West Antarctica, taking its mass into the Amundsen Sea. The ice near to their grounding lines - the places where the ice streams lift up off the land and begin to float out over the ocean - is now thinning by between four and eight metres per year.
For further details, see the item on the BBC News - Science and Environment website.
10 December 2013
The 2010 cold spot (red) was just south of a ridge running between Dome A and Dome F
The coldest place on Earth has been measured by satellite to be a bitter minus 93.2 Celsius (-135.8F).
As one might expect, it is in the heart of Antarctica, and was recorded on 10 August 2010. Researchers say it is a preliminary figure, and as they refine data from various space-borne thermal sensors it is quite likely they will determine an even colder figure by a degree or so. The previous record low of minus 89.2C was also measured in Antarctica. This occurred at the Russian Vostok base on 21 July 1983.
It should be stated this was an air temperature taken a couple of metres above the surface, and the satellite figure is the "skin" temperature of the ice surface itself. But the corresponding air temperature would almost certainly beat the Vostok mark.
For further details, see the item on the BBC News - Science and Environment website.
5 December 2013
More than thirty new, and, as yet unclassified, species of marine life were discovered during a science expedition to the Amundsen Sea off Pine Island Bay in Antarctica. The Amundsen Sea is one of the least explored areas of the Southern Ocean. It contains several deep troughs and basins formed during previous ice ages. Some are more than 1,600 metres deep.
In 2008 a team of marine biologists from British Antarctic Survey (BAS) and collaborating institutes took part in a summer research cruise on the RRS James Clark Ross to study the sea-bed fauna in the area. Their findings are now reported in Continental Shelf Research, following a lengthy period in which experts from all over the world were asked to help identify the animals. The process of categorisation is still going on.
5 December 2013
Brooding is a usual behaviour in animals. However, to observe it in a marine worm is exceptional and, more surprisingly, it guards eggs from external threats. The scientific finding, published recently in the journal Polar Biology, was developed by a group of researchers in Spain and at Harvard. The study was led by Professor Conxita Àvila, from the Department of Animal Biology of the University of Barcelona (UB), who coordinates the project Actiquim developed in Antarctica.
Nemerteans are a group of invertebrates mainly found in marine waters. The research group, led by Professor Àvila, discovered a new species of nemerteans, Antarctonemertes riesgoae, which has a reproductive strategy unique in this group: it broods like hens.
In marine Antarctic waters, UB experts found some 2-3 cm long cocoons brooded by female nemerteans. During reproduction, females secrete a very dense mucous through the body wall which solidifies on contact with marine water, creating an elastic layer. Once the cocoon is created, the female lays eggs and lies on top of them. Unexpectedly, they act in a non-passive way: when cocoons are disturbed, females show a defensive behaviour and go out through cocoons' openings.
For more details, read the news item on the University of Barcelona website, the article on the Fish Information and Services website, or read the original paper in Polar Biology.
29 November 2013
The Secretariat of the World Meteorological Organization issues bulletins containing information on the state of the ozone layer in Antarctica and surrounding regions at roughly two week intervals from August to November. The bulletins are based on data provided by WMO Members which operate ozone monitoring stations in the southern hemisphere and satellites to observe ozone globally. Meteorological data and model results are also used to assess and interpret the observations.
For more information, visit the WMO website.
29 November 2013
The sudden drainage of thousands of small lakes on the surface of Antarctic glaciers seems to have triggered the spectacular collapse of the Larsen B ice shelf in March 2012.
Some 3,000 small ponds of liquid water had emerged over the course of a decade on top of glaciers surrounding the ice shelf on the Antarctic Peninsula. These ponds disappeared in striking synchronicity a few days before the shelf's collapse.
When recreating the events in a computer simulation, Alison Banwell of the University of Chicago in Illinois and her colleagues found that the initial drainage of a single lake would have produced fractures in the ice that were capable of sucking dry neighbouring lakes, kicking off a catastrophic chain reaction.
The spread of fractures across the ice shelf may have ultimately caused its sudden demise, the authors suggest.
20 November 2013
Shifting, strengthening winds will help to counteract future sea-level rise in Antarctica — and by doing so, they may help to stabilize ice sheets on some parts of the southern continent.
The band of westerly winds that encircles Antarctica has been speeding up and creeping southwards since the 1950s. The trend, largely driven by the Antarctic ozone hole, is expected to continue thanks to climate change — and could alone cause a drop in sea level of up to 40 centimetres over 70 years, according to research led by Leela Frankcombe, a geophysicist at the Centre of Excellence for Climate System Science in Sydney, Australia.
6 November 2013
Tiny puffs of air from 1.5 million years ago may be locked inside bubbles in the ice nearly two miles beneath Antarctica's surface. That ancient air, if it exists, would be the oldest sample of Earth's atmosphere ever recovered.
"The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet," said lead author of the new study published in Climate of the Past, Hubertus Fischer of the University of Bern, Switzerland, in a press release.
During the transition, the Earth went from extreme warmth and cooling cycles alternating approximately every 41,000 years to having the cycles change only about every 100,000 years. Sediment samples drilled from the bottom of the ocean recorded the temperature differences, but scientists don't know why the global thermostat cycles slowed.
Ice samples from other areas yielded 800,000-year-old air bubbles. Those samples showed a lockstep correlation between higher greenhouse gas levels and increased temperatures over thousands of years, according to research published in Nature.
Greenhouse gases, such as methane and carbon dioxide, may have been the culprits behind the Mid-Pleistocene Transition, as well. However, drills will need to pluck a 2.4 to 3.2 kilometer-long (1.5 to 2 mile) ice core from the Antarctic ice to give scientists the 1.5 million-year-old sample they need.
"A deep drilling project in Antarctica could commence within the next three to five years," Fischer said. "This time would also be needed to plan the drilling logistically and create the funding for such an exciting large-scale international research project, which would cost around 50 million Euros."
28 October 2013
The effects of Antarctica's ozone hole may have spread much wider than previously thought. Ozone loss over the South Pole might be the reason for a two-decade rise in early summer temperatures across southern Africa, according to research published today in Nature Geoscience.
Desmond Manatsa, a climate scientist at Bindura University of Science in Zimbabwe, and colleagues analysed data sets of southern African climate from 1979 to 2010, covering the years before and after the development of the ozone hole over the Antarctic. They found that the size of the ozone hole seemed to influence wind patterns and triggered an upward shift in early summer temperatures.
Manatsa had been puzzled by the abrupt and seasonal increase in surface air temperatures in southern Africa. "The temperatures were actually significantly higher than those of other seasons and the rising assumed a shift rather than a slow and gradual manner," he says. The warming did not match what he expected to see from greenhouse-gas emissions.
Studies by others have previously shown that the Antarctic ozone hole has changed surface climates over the Antarctic and the Southern Ocean, as well as New Zealand, Patagonia and southern Australia. Manatsa shows that the climate effects of the ozone hole reach even farther. He found that a larger ozone hole coincided with a stronger summertime, continental, low-pressure system called the Angola Low, which brings in warm air from the lower latitudes to southern Africa, increasing surface air temperatures.
Anthropogenic chemicals known as chlorofluorocarbons released from aerosol spray cans, refrigerators and air conditioners have broken down some of the ozone in the stratosphere. The 1987 Montreal Protocol banned the release of these ozone-depleting substances in an attempt to reduce ozone thinning. Atmospheric monitoring shows that the ozone hole, which reached its greatest extent — 28.5 million square kilometres — in 2006, is shrinking, and several studies suggest that it might disappear by 2065.
If that occurs, summer temperatures in southern Africa might cool. "It is my belief that [the] long-term forecasts for the region, not only for surface air temperature but also for the summer rainfall, may need some revisiting," says Manatsa.
7 October 2013
Scientists have discovered huge ice channels beneath a floating ice shelf in Antarctica. At 250 metres high, the channels are almost as tall as the Eiffel tower and stretch hundreds of kilometres along the ice shelf. The channels are likely to influence the stability of the ice shelf and their discovery will help researchers understand how the ice will respond to changing environmental conditions.
24 September 2013
Much attention is paid to melting sea ice in the Arctic. But less clear is the situation on the other side of the planet. Despite warmer air and oceans, there's more sea ice in Antarctica now than in the 1970s – a fact often pounced on by global warming sceptics. The latest numbers suggest the Antarctic sea ice may be heading toward a record high this year.
While changes in weather may play a big role in short-term changes in sea ice seen in the past couple of months, changes in winds have apparently led to the more general upward sea ice trend during the past few decades, according to University of Washington research. A new modelling study to be published in the Journal of Climate shows that stronger polar winds lead to an increase in Antarctic sea ice, even in a warming climate. The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging. Stronger winds also drive ice faster, which leads to still more deformation and ridging. This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice to the blistering cold winds that cause more ice growth.
The study suggests that stronger westerly winds swirling around the South Pole can explain 80 percent of the increase in Antarctic sea ice volume in the past three decades.
19 September 2013
New results on Southern Ocean mixing, just published in Nature, from the DIMES team, including Southern Ocean Observing System (SOOS) Scientific Steering Committee member Alberto Naveira Garabato and Co-Chair Mike Meredith.
A mystery in the ocean near Antarctica has been solved by researchers who have long puzzled over how deep and mid-depth ocean waters are mixed. They found that sea water mixes dramatically as it rushes over undersea mountains in Drake Passage - the channel between the southern tip of South America and the Antarctic continent. Mixing of water layers in the oceans is crucial in regulating the Earth's climate and ocean currents.
The research provides insight for climate models which until now have lacked the detailed information on ocean mixing needed to provide accurate long-term climate projections. The study was carried out by the universities of Exeter, East Anglia and Southampton, the Woods Hole Oceanographic Institution, the British Antarctic Survey and the Scottish Association for Marine Science (SAMS).
18 September 2013
New research has revealed that more ice leaves Antarctica by melting from the underside of submerged ice shelves than was previously thought, accounting for as much as 90 per cent of ice loss in some areas. Iceberg production and melting causes 2,800 cubic kilometres of ice to leave the Antarctic ice sheet every year. Most of this is replaced by snowfall but any imbalance contributes to a change in global sea level.
For many decades, experts have believed that the most important process responsible for this huge loss was iceberg calving - the breaking off of chunks of ice at the edge of a glacier. New research, led by academics at the University of Bristol, with colleagues at Utrecht University and the University of California, has used satellite and climate model data to prove that this sub-shelf melting has as large an impact as iceberg calving for Antarctica as a whole and for some areas is far more important. The findings, published in the journal Nature, are crucial for understanding how the ice sheet interacts with the rest of the climate system and particularly the ocean.
During the last decade, the Antarctic ice-sheet has been losing an increasing amount of its volume. The annual turnover of ice equates to 700 times the four cubic kilometres per year which makes up the entire domestic water supply for the UK. Ice shelves which are thinning already were identified as losing most of their mass from this melting, a finding which will be a good indicator for which ice shelves may be particularly vulnerable to changes in ocean warming in the future.
16 September 2013
Evidence of diverse life forms dating back nearly a hundred thousand years has been found in subglacial lake sediments.
The possibility that extreme life forms might exist in the cold and dark lakes hidden kilometres beneath the Antarctic ice sheet has fascinated scientists for decades. However, direct sampling of these lakes in the interior of Antarctica continues to present major technological challenges. Recognising this, scientists from the British Antarctic Survey (BAS), and the Universities of Northumbria and Edinburgh in the UK, have been searching around the retreating margins of the ice sheet for subglacial lakes that are becoming exposed for the first time since they were buried more than 100,000 years ago. This is because parts of the ice sheet are melting and retreating at unprecedented rates as the temperature rises at the poles.
The group targeted Lake Hodgson on the Antarctic Peninsula, which was covered by more than 400 metres of ice at the end of the last Ice Age, but is now considered to be an emerging subglacial lake, with a thin covering of just 3–4 metres of ice. Drilling through the ice, they used clean coring techniques to delve into the sediments at the bottom of the lake.
The lake was thought to be a harsh environment for any form of life but the layers of mud at the bottom of the lake represent a time capsule storing the DNA of the microbes which have lived there throughout the millennia. The top few centimetres of the core contained current and recent organisms which inhabit the lake but, once the core reached 3.2 m deep, the microbes found most likely date back nearly 100,000 years.
Some of the life discovered was in the form of Fossil DNA showing that many different types of bacteria live there, including a range of extremophiles which are species adapted to the most extreme environments. These use a variety of chemical methods to sustain life both with and without oxygen. One DNA sequence was related to the most ancient organisms known on Earth and parts of the DNA in twenty three percent has not been previously described. Many of the species are likely to be new to science, making clean exploration of the remote lakes isolated under the deeper parts of the ice sheet even more pressing. Scientists believe organisms living in subglacial lakes could hold clues for how life might survive on other planets.
The paper, "Preliminary Analysis of Life within a Former Subglacial Lake Sediment in Antarctica" has been published online in the Journal 'Diversity' as part of a special issue on Microbial Ecology and Diversity.
For more information, please see the item on the British Antarctic Survey website.
12 September 2013
The results of research conducted by Wilson et al. in Geophysical Research Letters mark the beginning of a new paradigm for our understanding of the history of Earth's great global ice sheets. The research shows that an ice sheet on West Antarctica existed 20 million years earlier than previously thought.
The findings indicate that ice sheets first grew on the West Antarctic subcontinent at the start of a global transition from warm greenhouse conditions to a cool icehouse climate 34 million years ago. Previous computer simulations were unable to produce the amount of ice that geological records suggest existed at that time because neighbouring East Antarctica alone could not support it.
For more details, see the original paper in Geophysical Research Letters.
Douglas S. Wilson, David Pollard, Robert M. DeConto, Stewart S.R. Jamieson, Bruce P. Luyendyk. Initiation of the West Antarctic Ice Sheet and estimates of total Antarctic ice volume in the earliest Oligocene. Geophysical Research Letters, 2013; DOI: 10.1002/grl.50797
5 September 2013
Increases in temperature on the Antarctic Peninsula during the latter part of the 20th century were accompanied by an acceleration in moss growth, scientists have learned. Writing in the journal Current Biology, they describe the activity as unprecedented in the last 150 years.
The Peninsula sustains moss banks, some of which are more than 5000 years old. A team from the British Antarctic Survey (BAS), the University of Cambridge and the University of Exeter sampled the most southerly known moss bank, at Lazarev Bay on Alexander Island, in 2008. The researchers extracted a short peat core from the bank and, using radiocarbon dating techniques, ascertained the start of peat accumulation to have been around the year 1860. Microscopic tests established it was formed from a single species (Polytrichum strictum).
The Antarctic Peninsula is known to have witnessed significant warming since the 1950s, when official records started. Records from the BAS Rothera research station show the Peninsula warmed by between 1 and 1.4°C per decade during the 1980s and '90s. Along with one of the fastest rates of warming anywhere on the planet, the Peninsula has also seen significant increases in precipitation. The length of the melt season has been steadily increasing since 1948, with earlier thawing and later freezing extending the growing season.
The sampled moss bank accumulated at around 1.25 mm a year throughout the late 19th and early 20th centuries, then increased its growth rate from the mid-1950s to reach 5mm a year by the late 1970s. It is now estimated to be 3.5mm a year.
Lead author, Jessica Royles, from BAS and the University of Cambridge, said: "This moss bank provided a unique archive of growing conditions on the Antarctic Peninsula over the past one hundred and fifty years. By combining multiple analyses we have clearly demonstrated a substantial increase in plant growth since the 1960s, coincident with changes to the local climate."
The biological records in this region stretch back further than the meteorological records do, so this latest research will help scientists improve their understanding of the interaction between diversity and climate.
5 September 2013
Spatial and temporal variations in EAIS glacier terminus position from all measure-
|The world's thickest ice sheet may be at greater risk from variations in the climate than previously believed.
Scientists found that glaciers on the East Antarctic Ice Sheet (EAIS) advance and retreat in synch with changes in temperature.
Researchers at Durham University looked at declassified spy satellite imagery dating from 1963 to 2012. They used the pictures to detect changes in 175 glaciers as they flow into the sea along the 5,400km of coastline. They found a strong pattern of ebb and flow. In the 1970s and 80s, when temperatures were rising they found that 63% of glaciers were retreating. During the 1990s, when temperatures decreased, 72% of the glaciers advanced.
For more information, see the original Nature - Letter article.
4 September 2013
The thinning of the atmosphere's ozone layer could be contributing to warming the planet, according to a study published this week in Geophysical Research Letters.
Kevin Grise, an atmospheric scientist at Columbia University in New York, and his team modelled the weather dynamics around the ozone hole above the Antarctic. They calculated the knock-on effects of ozone depletion on cloud cover, and ultimately on radiative forcing — the balance of solar and thermal radiation absorbed, reflected or emitted by the planet and its atmosphere.
The team's models predicted a shift in the southern-hemisphere jet stream — the high-altitude air currents flowing around Antarctica — as a result of ozone depletion. This produced a change in the cloud distribution, with clouds moving towards the South Pole, where they are less effective at reflecting solar radiation.
27 August 2013
When you drop a whale backbone into Antarctic waters and retrieve it a year later, you'll find it covered with a pelt of wriggling, rosy-hued worms. Drop a chunk of wood in the same spot, and you'll discover that it's hardly changed. That's the result of a simple experiment to find out if some of the world's weirdest worms also live in Antarctic waters. The discovery extends the range of bone-eating worms to the Southern Ocean and suggests that Antarctic shipwrecks may be remarkably intact.
For more details, see the article on the Science Now website or read the original paper in the Proceedings of the Royal Society B.
1 August 2013
The Report from the 8th Session of the CLIVAR/CliC/SCAR Southern Ocean Panel (SOP), held in Hobart, Australia from 21st to 22nd February 2013, is now available. The SOP meetings occur every 15 to 18 months, often scaffolded onto other relevant meetings the panel members would be attending. In this case, the meeting was held in conjunction with a workshop on sea level rise.
Attendees of the meeting included 9 members of the SOP and 13 other invited experts, including representatives from the modelling, palaeo-, and early-career scientist communities. Discussions focused on: the status of SOOS and the under ice observations workshop; the use of the C-SOBOM program (Center for Southern Ocean Biogeochemical Observations and Modeling); Antarctica 2K Working Group activities; and a joint session with the CLIVAR Working Group on Ocean Model Development (WGOMD).
1 August 2013
The ESA Climate Change Initiative (CCI) Program has asked for input from the community about which Antarctic satellite data products would be most valuable. They invite you, as a possible future user of these data products, to provide recommendations and feedback about what products you think it would be most useful for an Antarctic CCI project to focus on. To help them assess the user requirements for satellite based Antarctic ice sheet data products, please complete the short on-line survey, containing just 16 multiple choice questions which take only ten minutes to complete. The survey will remain open until 16 September 2013.
1 August 2013
Life with a young child can sometimes be challenging - but how would you feel if you were bringing up your son in Antarctica?
Fernando Font, an officer in the Chilean Air Force, made the tough decision to move his wife Carolina and young son, also called Fernando, to Antarctica for two years while he serves as head of air operations on King George Island. For Carolina, the move involved a huge amount of organisation - including buying nearly 2,500 nappies in advance and shipping them over. But both insist that living in Antarctica has only improved their family life.
BBC News travelled to King George Island to meet them. Watch the video on the BBC News Magazine website.
1 August 2013
In events that could exacerbate sea level rise over the coming decades, stretches of ice on the coasts of Antarctica and Greenland are at risk of rapidly cracking apart and falling into the ocean, according to new iceberg calving simulations from the University of Michigan.
1 August 2013
A review article on the progress of Chinese research in the physical oceanography of the Southern Ocean over the past 30 years has recently been published in the journal Advances in Polar Science.
Oceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expedition since 1984. Using the field data obtained in these surveys and the results from remote sensing and numerical models, Chinese physical oceanographers have investigated the water masses, fronts and circulation patterns in the Southern Ocean. Most oceanographic observations have been conducted in Prydz Bay and the adjacent seas. Conductivity, temperature and depth data (CTD) have been applied to study several features of the water masses in this region, including the spatial variation of warm summer surface water, the northward extension of shelf water, the flow of ice shelf water from the cavity beneath the Amery Ice Shelf, the upwelling of the Circumpolar Deep Water, and the formation of the Antarctic Bottom Water.
For more details, please see the review in Advances in Polar Science.
22 July 2013
An explosion in glass sponge population has forced researchers to rethink how animals live in Antarctica.
Conventional wisdom holds that life in Antarctica moves at a glacial pace. Marine creatures called sponges, which live on the seafloor, have been known to go a decade without any measurable growth in the Antarctic. But that thinking has changed, in part because of a startling discovery off the eastern coast of the Antarctic Peninsula.
Researchers have found a "boomtown" of sponges. In a study published in the journal Current Biology, they report on the explosion of a community of glass sponges - organisms with skeletons made of silica, a mineral component of glass - on the seafloor below where an enormous ice shelf used to be.
These sponges - filter feeders not known for their rapid development - doubled in biomass and tripled in number over the course of two growing seasons.
For more details, see the item on the National Geographic website, view the press release on the Alfred Wegener Institute website or read the paper in Current Biology.
22 July 2013
Pine Island Glacier (PIG), the longest and fastest flowing glacier in the Antarctic, has spawned a huge iceberg. The block measures about 720 sq km in area - roughly eight times the size of Manhattan Island in New York.
Scientists have been waiting for the PIG to calve since October 2011 when they first noticed a spectacular crack spreading across its surface. Confirmation that the fissure had extended the full width of the glacier was obtained on Monday when it was seen by the German TerraSAR-X satellite. This carries a radar instrument that can detect the surface of the ice stream even though the Antarctic is currently in the grip of winter darkness.
The glacier's behaviour means it is now under close scrutiny, not least because it drains something like 10% of all the ice flowing off the west of the continent.
"The PIG is the most rapidly shrinking glacier on the planet," explained Prof David Vaughan from the British Antarctic Survey (BAS). "It's losing more ice than any other glacier on the planet, and it's contributing to sea level rise faster than any other glacier on the planet. That makes it worthy of study."
For more information, please see the item on the BBC News - Science and Environment website.
22 July 2013
A giant lake buried more than two miles beneath the Antarctic ice has been found to contain a "surprising" variety of life.
Analysis of ice cores obtained from the basin of Lake Vostok, the subglacial lake that Russian scientists drilled down to in 2012, have revealed DNA from an estimated 3,507 organisms. While the majority were found to be bacteria, many of which were new to science, there were also other single celled organisms and multicellular organisms found, including from fungi. The diversity of life from the lake has surprised scientists as many had thought the lake would be sterile due to the extreme conditions.
22 July 2013
Recent scientific interest, following the "discovery" of lithodid crabs around Antarctica, has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. The authors, however, conclude there is no evidence for a modern-day "crab invasion" and recommend a repeated targeted lithodid sampling programme along the West Antarctic shelf to fully test the validity of the "invasion hypothesis".
For more information, please read the original research article in PLOS One.
22 July 2013
Scientists have seen evidence for a colossal flood under Antarctica that drained six billion tonnes of water, quite possibly straight to the ocean.
The cause is thought to be a deeply buried lake that suddenly over-topped. Satellites were used to map the crater that developed as the 2.7km-thick overlying ice sheet slumped to fill the void left by the escaping water. The location of the flood was Cook Sub-Glacial Lake (SGL) in the east of the continent, and the event itself occurred over a period of about 18 months in 2007-2008. It was detected and described using a combination of data gathered by the now-retired US Icesat mission and Europe's new Cryosat platform.
At present, Antarctica is losing mass at a rate of 50-100 billion tonnes a year, helping to raise global sea level. This study suggests that a not insignificant fraction of this mass loss could be due to flood events like that seen at Cook SGL. "This one lake on its own represents 5-10% of [Antarctica's] annual mass imbalance," said Leeds co-author Prof Andy Shepherd.
For further details, see the item on the BBC News - Science and Environment website or read the original paper in Geophysical Research Letters.
28 June 2013
A hairy crab named after David Hasselhoff hitched a ride on an ocean "super-highway" to cross from the Pacific to the Atlantic millions of years ago.
In a study published in the journal Proceedings of the Royal Society B, Dr Christopher Roterman and colleagues propose that the "Hoff crab" probably originated around the vents that populate mid-ocean ridges in the eastern Pacific Ocean. It then expanded into the Atlantic through the Drake Passage that separates South America and Antarctica, spreading along volcanic vent regions that are now extinct.
The crab appears to have exploited the ocean current known as the Antarctic Circumpolar Current (ACC), which flows in a clockwise direction, west to east around Antarctica, through the Drake Passage.
For more information, please see the item on the BBC News - Science and Environment website or read the full paper in the Proceedings of the Royal Society B.
28 June 2013
Scientists have found a potential building block for life in a Martian meteorite recovered from Antarctica. Parts of the rock contain rich concentrations of boron, which biochemists suspect played a key role in the development of ribonucleic acid, or RNA.
Read more on the News Discovery website.
28 June 2013
More than half of the melting of Antarctica's ice occurs at just ten small ice shelves.
Ice shelves are portions of the larger ice sheet that extend over the ocean, floating on seawater. Conventional wisdom once held that calving, the break off of large chunks of ice, was the main factor driving ice-shelf dynamics, but recent research has underscored the role of melting from below, or 'basal' melting. Capitalizing on newly available monitoring data as well as recent modelling, a team of scientists led by Eric Rignot at the University of California, Irvine, has for the first time quantified this effect for the entire continent.
The results, which appear in Science, suggest that warm ocean currents are melting ice shelves predominantly at certain locations around the continent, to an extent that accounts for 55% of the annual meltwater. The findings will help scientists to tackle larger questions about how the Antarctic ice sheet might change in future and its contribution to global sea-level rise.
For more information, please read the Nature News item or read the full paper:
Rignot, E., Jacobs, S., Mouginot, J. & Scheuchl, B. Science DOI: 10.1126/science.1235798
6 June 2013
A recent key paper has been published in the journal Nature, following from the ISMASS workshop held at the XXXII SCAR Open Science Conference and Meetings, in Portland, Oregon in July 2012.
Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. The review discusses the past six years of progress and examines the key problems that remain.
(a) Warm modified Circumpolar Deep Water (mCDW) leads to melting at the grounding line,
For more information, see the full review article in Nature.
4 June 2013
An ice shelf is a thick plate of ice attached to a coastline on one side and floating over the ocean on the other side. Many ice shelves fringe Antarctica, including the Wilkins Ice Shelf on the Antarctic Peninsula, which underwent a series of breakup events in 1998, 2008, and 2009.
Just as earthquakes can sometimes leave landscapes more prone to future quakes, the breakups on the Wilkins Ice Shelf left it vulnerable to further disintegration. In addition, the sea ice that had long pressed the shelf up against the coastline moved out, putting the remnants of the shelf in direct contact with open water. Ocean waves went to work on the ice, and in early 2013 the fracturing continued.
For further details, see the article on the NASA Earth Observatory website.
31 May 2013
Researchers publishing a paper in the latest issue of the journal Science have found, through Antarctic planktonic ice core examinations, that the continental ice cap formed more than 33 million years ago.
The ice cap was formed during the Oligocene (33.6 million years ago), according to carbon dating of the research data. Prior to the Oligocene, the southern continent had a warm tropical climate, teeming with life. However, when the cold came, most life forms died. Those that were able to adapt to the change, survived throughout time to the present age.
The paleoclimatic information was obtained through the work of the Integrated Ocean Drilling Program (IODP) expedition, which bore down into the sediment strata of the Antarctic depths to the preserved fossils. Carlota Escutia, co-chief officer of the new SCAR SRP Past Antarctic Ice Sheet Dynamics (PAIS), said the "fossil record of dinoflagellate cyst communities reflects the substantial reduction and specialization of these species that took place when the ice cap became established and, with it, marked seasonal ice-pack formation and melting began."
Dinoflagellates evolved into more simplified organisms enabling them to survive the formation of the Antarctic ice cap as well as thrive in the continual melting and freezing of the ice sheet during the seasonal changes. Over the course of millions of years, the dinoflagellates continued to evolve to assume their present-day form.
As the ice-pack melts during the approaching summer, an increase in productivity of endemic plankton communities occurs. The ice melt frees the nutrients it has accumulated throughout the previous year and releases it for consumption by plankton. "This phenomenon influences the dynamics of global primary productivity," said Dr. Escutia in a statement.
The dinoflagellate communities have continued to evolve throughout history of the ice pack. However, Escutia thinks: "the great change came when the species simplified their form and found they were forced to adapt to the new climatic conditions."
24 May 2013
The puzzle of why the penguin is unable to fly may have finally been solved. Researchers believe that the bird's underwater prowess may have cost it its ability to fly.
A study published in the Proceedings of the National Academy of Sciences, looked at seabirds closely related to the penguin. The study's authors confirmed that a wing that is good for flying cannot also be good for diving and swimming.
Professor John Speakman, from the University of Aberdeen and the Chinese Academy of Sciences, said: "Like many people, I've always been interested in penguins, and seeing them do these phenomenal marches across the ice, I've often thought: 'Why don't they just fly?'"
For more information, see the item on the BBC News - Science and Environment website or read the full article on the PNAS website.
24 May 2013
Hot on the heels of detecting the two highest-energy neutrinos ever observed, scientists working with a mammoth particle detector buried in ice near the South Pole unveiled preliminary data showing that they also registered the signal of 26 additional high-energy neutrinos. The newfound neutrinos are somewhat less energetic than the two record-setters but nonetheless appear to carry more energy than would be expected if created by cosmic rays hitting the atmosphere — a prodigious source of neutrinos raining down on Earth. The particles thus may point to unknown energetic astrophysical processes deeper in the cosmos.
For more information, see the item on the Scientific American website.
15 May 2013
Weddell seals (Leptonychotes weddellii) are the only mammal that dares to swim long distances under sea ice, travelling up to 20 kilometres in hour-long bursts as they scan for air holes and an eventual exit somewhere in the midst of vast Antarctic sheets. There, mothers give birth so that their pups will be safe from leopard seals and killer whales. But how do those pups learn to navigate the risky underwater terrain so quickly? They're born with big brains, according to a study published online and in an forthcoming issue of Marine Mammal Science.
Researchers measured 12 carcasses and found that the brains of newborn pups are 70% the size of adult brains — the largest percentage of any mammal. In comparison, the brains of human babies are only 25% the size of adults. Good thing our trekking doesn't start until much later in life.
13 May 2013
|To catch Antarctic toothfish, you must bait your hook with Peruvian squid and cast it into the depths of the Ross Sea. This is what a team of Ukrainians did on a fishing trip near Antarctica. But sometimes, Mother Nature trips you up. Sometimes, you catch a hopbeard plunderfish.
In 2009-10, Ukrainian mariners happened to pull up three fish that looked unfamiliar. Further analysis found that they were a previously undiscovered species, dubbed the hopbeard plunderfish and described in a study published online on 29 April in the journal ZooKeys. The fish bear the scientific name Pogonophryne neyelovi.
The strange-looking denizens of the deep have brownish-splotched bodies and are shaped somewhat like tadpoles, especially when young, according to the study. They have sharp dorsal fins that extend along the top of their bodies and strange "barbels," which resemble dirty Q-tips, that extend from their chins.
The Hopbeard Plunderfish (Pogonophryne neyelovi).
The longest of the three specimens measured 14 inches (35.5 centimetres). And they really like to live in the deep — they were pulled from depths of up to 4,560 feet (1,390 metres).
Currently, next to nothing is known about their behaviour, diet or what they do down there in the depths.
24 April 2013
Two ultra-high-energy neutrinos captured by the IceCube experiment probably came from outside the Galaxy, according to an analysis posted by the collaboration today.
IceCube consists of 86 strings of detectors sunk in a cubic kilometre of ice near the South Pole, which pick up the light emitted when neutrinos and other particles pass through.
22 April 2013
Antarctica has been mostly covered by ice since the inception of large-scale continental glaciation during the Oligocene, which profoundly altered the isotopic and mineralogical records of the sediments surrounding the continent. Houben et al. found records of the corresponding living systems in the fossil marine dinoflagellate cysts, which revealed that a microplankton ecosystem, similar to the one that exists today, appeared simultaneously with the first major Antarctic glaciation approximately 34 million years ago.
For more information, see the full article in Science.
10 April 2013
The summer melting season in the Antarctic Peninsula has lengthened over the last 60 years, new research shows. This is contributing to sea-level rise, and may be linked to the rapid break-up of ice shelves in the area.
The Antarctic Peninsula, a mountainous finger of land pointing northwards towards South America, is warming much faster than the rest of Antarctica. Temperatures have risen by almost 3°C since the 1950s – three times faster than the global average. Scientists think this is because local westerly winds are getting stronger, pushing warmer air from the sea up and over the peninsula. Unusually for Antarctica, summer temperatures in the warmest few months are often high enough for snow to melt.
Melted snow running into the sea causes sea-levels to rise, but the longer melting season can have other important effects. Meltwater gathers in cracks in floating ice shelves, where the sheer weight of water can enlarge the cracks and shatter the ice, leading to retreat or collapse of the ice shelf.
With the physical barrier of the ice shelf removed, glaciers can flow into the sea faster, with a further impact on sea level. Also, melting and refreezing causes snow layers to become thinner and denser, affecting the height of the snow surface above sea level. Scientists need to know this so they can interpret satellite data correctly.
For more information, see the item on the NERC Planet Earth Online website or read the full article in the Journal of Geophysical Research: Earth Surface.
10 April 2013
Research published this month, in the journal Nature Geoscience, concludes that oceanographic reorganisations and biological processes are linked to the supply of airborne dust in the Southern Ocean and this connection played a key role in past rapid fluctuations of atmospheric carbon dioxide levels, an important component in the climate system.
The scientists studied a marine sediment core from the Southern Ocean and reconstructed chemical signatures at different water depths using stable isotope ratios in the shells of foraminifera, single-celled marine organisms. They found that the chemical difference between intermediate level and deep waters over the last 300,000 years closely resembled the changes in atmospheric carbon dioxide levels and the input of windblown dust.
2 April 2013
Global warming is expanding the extent of sea ice around Antarctica in winter in a paradoxical shift caused by cold plumes of summer melt water that re-freeze fast when temperatures drop, a recent study has shown. An increasing summer thaw of ice on the edges of Antarctica, twinned with less than expected snowfall on the frozen continent, is also adding slightly to sea level rise in a threat to low-lying areas around the world, the study said.
Scientists have been struggling to explain why sea ice around Antarctica has been growing, reaching a record extent in the winter of 2010, when ice on the Arctic Ocean at the other end of the planet shrank to a record low in 2012.
"Sea ice around Antarctica is increasing despite the warming global climate," said Richard Bintanja, lead author of the study at the Royal Netherlands Meteorological Institute. "This is caused by melting of the ice sheets from below," he said of the findings in the journal Nature Geoscience.
Ice is made of fresh water and, when ice shelves on the fringes of Antarctica thaw in summer because of upwellings of warming sea water, the meltwater forms a cool layer that floats on the denser, warmer salty sea water below, the study said. In winter, the melt water readily turns to ice because it freezes at zero degrees Celsius, above sea water at -2C (28.4F).
28 March 2013
A joint Press Release has been issued by the Russian Arctic and Antarctic Research Institute and the St. Petersburg Institute of Nuclear Physics on a possible new type of bacteria discovered in water samples from subglacial Lake Vostok, lifted by the drill after entering the lake on the 5th Febuary 2012.
25 March 2013
The waters of the Southern Ocean now take up about 50% of the atmospheric carbon dioxide emitted by human activities, thanks in large part to the so-called "biological pump." Phytoplankton, tiny photosynthesizing organisms that bloom in the nutrient-rich waters of the Southern Ocean, suck up carbon dioxide from the atmosphere. When the creatures die, they sink to the ocean floor, effectively sequestering that carbon for hundreds or even thousands of years. It also helps that carbon dioxide is more soluble in colder waters, and that the churning winds mix the waters at the surface, allowing the gases to penetrate the waters more easily.
There are signs, however, that the ocean's capacity to sequester atmospheric carbon dioxide has been decreasing over the past few decades. Previous ocean sediment records suggest that, as the world slipped into the last glacial period, less carbon overall reached the sediments of the Southern Ocean, coinciding with declining atmospheric carbon dioxide. During cold periods, increased sea-ice cover can keep gases trapped in the ocean and the drier, dustier conditions bring much-needed iron to phytoplankton in the sub-Antarctic portion of the Southern Ocean, feeding blooms that gobble down carbon dioxide from the atmosphere.
What happens when the world moves into a warm, interglacial period isn't certain, but in 2009, a paper published in Science by researchers found that upwelling in the Southern Ocean increased as the last ice age waned, correlated to a rapid rise in atmospheric carbon dioxide. Now, using two deep cores collected at two Ocean Drilling Program sites in the Southern Ocean, Jaccard and colleagues have reconstructed ocean records of productivity and vertical overturning reaching back a million years, through multiple glacial-interglacial cycles. This rapid increase in carbon dioxide as the world transitions from glacial to interglacial seems to be a pretty regular thing, they've found.
For more information, read the full Science Now article.
25 March 2013
Marine biologists have, for the first time, found a whale skeleton on the ocean floor near Antarctica, giving new insights into life in the sea depths. The discovery was made almost a mile below the surface in an undersea crater and includes the find of at least nine new species of deep-sea organisms thriving on the bones.
"The planet's largest animals are also a part of the ecology of the very deep ocean, providing a rich habitat of food and shelter for deep sea animals for many years after their death," says Diva Amon, lead author of the paper based at University of Southampton Ocean and Earth Science (which is based at the UK's National Oceanography Centre) and the Natural History Museum. "Examining the remains of this southern Minke whale gives insight into how nutrients are recycled in the ocean, which may be a globally important process in our oceans."
Worldwide, only six natural whale skeletons have ever been found on the seafloor. Scientists have previously studied whale carcasses, known as a 'whale fall', by sinking bones and whole carcasses. Despite large populations of whales in the Antarctic, whale falls have not been studied in this region until now.
When a whale dies and sinks to the ocean floor, scavengers quickly strip its flesh. Over time, other organisms then colonise the skeleton and gradually use up its remaining nutrients. Bacteria break down the fats stored in whale bones, for example, and in turn provide food for other marine life. Other animals commonly known as zombie worms can also digest whale bone.
"One of the great remaining mysteries of deep ocean biology is how these tiny invertebrates can spread between the isolated habitats these whale carcasses provide on the seafloor," says co-author Dr Adrian Glover at the Natural History Museum. 'Our discovery fills important gaps in this knowledge.'
For more information, read the full article in Deep-Sea Research II: Topical Studies in Oceanography.
25 March 2013
Distant, dust-filled galaxies were bursting with newborn stars much earlier in cosmic history than previously thought, according to newly published research. So-called "starburst galaxies" produce stars at the equivalent of a thousand new suns per year. Now, astronomers have found starbursts that were churning out stars when the universe was just a billion years old.
"I find that pretty amazing," said Joaquin Vieira, a postdoctoral scholar at the California Institute of Technology and leader of the study. "These aren't normal galaxies. These galaxies [reveal star formation] at an extraordinary rate, when the universe was very young. I don't think anyone expected us to find galaxies like this so early in the history of the universe."
An international team of astronomers, whose work is reported in the March 14 issue of the journal Nature, found dozens of these galaxies with the National Science Foundation (NSF)-funded South Pole Telescope (SPT). SPT is a 10-metre dish in Antarctica that surveys the sky in millimeter-wavelength light, whose waves fall between radio waves and infrared on the electromagnetic spectrum.
The team then took a more detailed look using the new Atacama Large Millimeter Array (ALMA) in Chile's Atacama Desert, which is funded in part by NSF. ALMA is an international facility and is a partnership between North America, Europe and East Asia in cooperation with the Republic of Chile.
"The new observations represent some of ALMA's most significant scientific results yet," Vieira said. "We couldn't have done this without the combination of SPT and ALMA. ALMA is so sensitive, it is going to change our view of the universe in many different ways."
4 March 2013
In an article in Science, Ed Brook discusses how, over the course of Earth history, it is generally believed that atmospheric carbon dioxide (CO2) and climate are closely coupled. The most direct evidence comes from polar ice cores. Snow falling in Antarctica and Greenland gradually compacts to form solid ice and trap air. Polar ice also records past temperatures in the ratio of heavy to light isotopes in the water molecule. Ice core analyses have shown that Antarctic temperature and atmospheric CO2 concentrations are highly correlated over the large-scale climate cycles of the past 800,000 years.
But which came first? Does CO2 drive climate cycles or is it a feedback in the system that contributes to warming? In another article in Science, Parrenin et al address this question in a study of CO2 concentrations and Antarctic temperatures during the last deglaciation. They conclude that temperature and CO2 changed synchronously.
For more information, read the articles on the Science website:
- Edward J Brook - Leads and Lags at the End of the Last Ice Age
- Parrenin et al - Synchronous Change of Atmospheric CO2 and Antarctic Temperature During the Last Deglacial Warming
25 February 2013
|A group of researchers from the National Oceanography Center in Southampton has discovered a strange new deep-sea volcanic vent at Hook Ridge near the South Shetland Islands, Antarctica.
Hydrothermal vents are like hot springs, spewing jets of water from the seafloor out into the ocean. The expelled water, if hot enough, is rich in dissolved metals and other chemicals that can nourish a host of strange-looking life, via a process called 'chemosynthesis.' The hot water, being more buoyant than the surrounding cold seawater, rises up like a fountain or 'plume,' spreading the chemical signature up and out from the source.
The newly discovered vent, named the Hook Ridge vent, however, was found to lack the high temperatures and alien-like creatures that scientists associate with hot hydrothermal vents. Instead there was a low-lying plume of shimmering water, caused by differences relative to the surrounding seawater in certain properties, such as salinity.
"Geochemical measurements of the water column provided evidence of slightly reducing, localized plumes close to the seafloor at Hook Ridge," said Dr Alfred Aquilina, lead author of the study published in the journal PLOS ONE.
Location map of the Bransfield Strait in the Southern
"We therefore went in with sled-mounted cameras towed behind the Royal Research Ship James Cook and saw shimmering water above the seafloor, evidence of hydrothermal fluid seeping through the sediment."
So why were there no strange creatures around the vent? The team investigated this particular area of the deep-sea because prior measurements of the water column above Hook Ridge detected chemical changes consistent with a hydrothermal plume. On investigation, there was also a small relict 'chimney' of precipitated minerals on the seafloor, which suggests that the hydrothermal fluid flowing from the vent was once warmer.
The researchers therefore propose that hydrothermal activity at Hook Ridge is too irregular to provide the vital chemicals that support chemosynthetic life.
"This region was investigated because hydrothermal systems in this part of the Southern Ocean may potentially act as stepping stones for genetic material migrating between separate areas in the world ocean," Dr Aquilina said. "The more hydrothermal vents we can find and investigate, the more we can understand about the evolution and dispersal of the creatures that live off the chemicals expelled in these dark, deep environments."
25 February 2013
By tracking the voyages of elephant seals off Antarctica, and with the help of satellite imaging and undersea sensors, researchers have discovered a long-elusive source for the deep-ocean streams of cold water that help to regulate the Earth's climate.
Three sources of Antarctic Bottom Water (AABW) were known until now. The first, in the Weddell Sea, was found in 1940; two others were found in the Ross Sea and along the Adélie Coast of East Antarctica in the 1960s and '70s. But for years, researchers have suggested that these were not the only ones. In particular, water samples from an area called the Weddell Gyre contain atmospheric pollutants known as chlorofluorocarbons (CFCs), indicating that the deep water came into contact with the air far too recently to have been carried there from one of the known AABW sinks.
Now, Kay Ohshima, a physical oceanographer at Hokkaido University in Sapporo, Japan, and his colleagues have traced that water to a fourth AABW source, in the Cape Darnley polynya. Their results are published in Nature Geoscience.
Dr Mike Meredith, a polar oceanographer at BAS and co-chair of the Southern Ocean Observing System (www.soos.aq), who wrote an accompanying commentary on the study, says that if the total rate of AABW formation declines, the resulting changes in cold-water circulation could have important effects on global climate, letting the ocean depths warm and thereby changing the rate of heat exchange between Antarctica and the tropics. Moreover, he says, sea levels could rise — owing to the fact that water expands as it warms — and temperature changes could affect deep-sea ecosystems
For further details, see the item on the Nature - News website, read Mike Meredith's article in Nature Geoscience - News and Views or read the full paper in Nature Geoscience.
7 February 2013
Last week, the US WISSARD team found and collected microbes in a lake hidden under more than a half-mile of ice.Among other things, the discovery may shed light on what lies under the icy moons of Jupiter and Saturn.
The newfound life-forms have little connection to life on the earth's surface and many apparently survive by "eating rocks," team member Brent Christner said in an interview from the U.S. McMurdo Station, after spending several weeks working at a remote field site at Lake Whillans. That may explain how life on other celestial objects — such as on the moons of Jupiter and Saturn — survive in the absence of available carbon.
"The conditions faced by organisms in Lake Whillans are quite parallel to what we think it would be like on those icy moons," Christner said. "What we found tells us a lot about extreme life on Earth," and how similar life beyond Earth might survive.
6 February 2013
As the combined effects of Antarctic stratospheric ozone depletion and climate warming have forced the westerly surface winds in the Southern Hemisphere to shift toward the pole, mixing between the upper ocean and deeper waters has also changed.
Waugh et al. now show that water originating at the surface at subtropical latitudes is mixing into the deeper ocean at a higher rate than 20 years ago, while the reverse is true for those originating at higher latitudes. The summer westerly winds that blow in the Southern Hemisphere have shifted toward the South Pole over the past several decades, but why?
Lee and Feldstein show that greenhouse gas forcing and ozone depletion impart different signatures to wind patterns and conclude that ozone depletion has been responsible for more than half of the observed shift.
For further details on both studies, please see the Science website:
Waugh et al - Vol. 339 no. 6119 pp. 568-570; DOI: 10.1126/science.1225411
Lee & Feldstein - Vol. 339 no. 6119 pp. 563-567; DOI: 10.1126/science.1225154
30 January 2013
A US National Science Foundation (NSF)-funded research team has successfully drilled through 800 metres (2,600 feet) of Antarctic ice to reach a subglacial lake and retrieve water and sediment samples that have been isolated from direct contact with the atmosphere for many thousands of years.
Scientists and drillers with the interdisciplinary Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) announced on 28 January local time that they had used a customized clean hot-water drill to directly obtain samples from the waters and sediments of subglacial Lake Whillans.
For further details, visit the WISSARD Project website.
22 January 2013
Details of Adelie penguin feeding behaviour have been filmed by Japanese scientists.
Using video cameras and accelerometers attached to free-swimming penguins, researchers have gained a unique insight into the birds' hunting techniques. Adelie penguins adopted different strategies depending on whether they were hunting fish or krill. The findings are published in the journal PNAS.
Lead scientist Dr Yuuki Watanabe from the National Institute of Polar Research in Tokyo, Japan, told BBC Nature: "Foraging is the most basic activity of animals, but details of foraging behaviour are poorly known, especially in marine animals."
For more details, please see the article on the BBC Nature News website.
17 January 2013
A major gap in predictive capability concerning the future evolution of the ice sheets was identified in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change. As a consequence, it has been suggested that the AR4 estimates of future sea-level rise from this source may have been underestimated. A recent study used a formalized pooling of expert views on uncertainties in the future contributions of melting ice sheets to sea-level rise, with a structured elicitation approach. Expert opinion is shown to be both very uncertain and undecided on the key issue of whether recent ice-sheet behaviour is a long-term trend or due to natural variability.
For further information, please read the article in Nature Climate Change.
8 January 2013
The report "Future Science Opportunities in Antarctica and the Southern Ocean" suggests actions for the United States to achieve success for the next generation of Antarctic and Southern Ocean science. The report highlights important areas of research by encapsulating each into a single, overarching question. The questions fall into two broad themes: (1) those related to global change, and (2) those related to fundamental discoveries. In addition, the report identifies key science questions that will drive research in Antarctica and the Southern Ocean in coming decades, and highlights opportunities to be leveraged to sustain and improve the US research efforts in the region.
The report is highly relevant to the planned SCAR Horizon Scanning Activity on Future Directions of Antarctica and Southern Ocean Science.
A PDF version of the full report can be retrieved from the National Academies Press website.
3 January 2013
|In a discovery that raises further concerns about the future contribution of Antarctica to sea level rise, a new study finds that the western part of the ice sheet is experiencing nearly twice as much warming as previously thought.
The temperature record from Byrd Station, a scientific outpost in the center of the West Antarctic Ice Sheet (WAIS), demonstrates a marked increase of 4.3 degrees Fahrenheit (2.4 degrees Celsius) in average annual temperature since 1958 — that is, three times faster than the average temperature rise around the globe. This temperature increase is nearly double what previous research has suggested, and reveals — for the first time — warming trends during the summer months of the Southern Hemisphere (December through February), said David Bromwich, Professor of Geography at Ohio State University and senior research scientist at the Byrd Polar Research Center.
The colour shadings show the correlation between the annual
mean temperatures at Byrd and the annual mean temperatures
at every other grid point in Antarctica. The correlations are computed using ERA-Interim 2-metre temperature time series from 1979 to 2011. The star symbol denotes the location of Byrd Station/AWS. The filled black circles denote the locations of permanent research stations with long-term temperature records (FV, Faraday/Vernadsky)
3 January 2013
An invasive species has the potential to drastically alter Antarctic ecosystems that have been isolated for millions of years, research suggests. A species of midge was able to release large volumes of nutrients into the soil, changing the way native species had lived and evolved, a UK team found. They added that the species was well-suited to thrive in the extreme conditions.
"In terms of function, their job is litter turnover - they help things decay in the soil - and the population density of this thing in the area where it has been introduced is responsible for more litter turnover than the community that was already there," explained co-presenter of the research Peter Convey, of the British Antarctic Survey and co-chief officer of SCAR's EBA programme. "So basically it is bringing a function into an ecosystem that is not very active already. In principle, it can be a fundamental change in the way that ecosystem works."
For further details, please see the news item on the BBC News - Science and Environment website.