Lake(s) Beneath The Antarctic Ice

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Source: The Earth Institute at Columbia University
Date: 2006-01-30
http://www.sciencedaily.com/releases/20 ... 032904.htm

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Two New Lakes Found Beneath Antarctic Ice Sheet

The Earth Institute at Columbia University--Lying beneath more than two miles of Antarctic ice, Lake Vostok may be the best-known and largest subglacial lake in the world, but it is not alone down there. Scientists have identified more than 145 other lakes trapped under the ice. Until now, however, none have approached Vostok's size or depth.

In the February 2006 issue of Geophysical Research Letters, scientists from the Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University, describe for the first time the size, depth and origin of Vostok's two largest neighbors. The two ice-bound lakes are referred to as 90ºE and Sovetskaya for the longitude of one and the Russian research station coincidentally built above the other. The scientists' findings also indicate that, as suspected with Lake Vostok, an exotic ecosystem may still be thriving in the icy waters 35 million years after being sealed off from the surface.

Geophysicists Robin Bell and Michael Studinger of Lamont-Doherty combined data from ice-penetrating radar, gravity surveys, satellite images, laser altimetry and records of a Soviet Antarctic Expedition that unknowingly traversed the lakes in 1958-1959. The shorelines of the lakes appeared in satellite images of the region as perturbations in the surface of the East Antarctic ice sheet. In addition, because the ice is effectively floating on the surface of the lakes, the ice sheet exhibits slight depressions over the lakes that appear in radar and laser elevations.

Bell and Studinger, along with colleagues from the University of New Hampshire and NASA, report that the 90ºE Lake has a surface area of 2,000km2, which is about the size of Rhode Island, and is second only to Lake Vostok's 14,000km2 surface area. Sovetskaya Lake was calculated to be about 1,600 km2. Both are sealed beneath more than two miles of ice.

The lake depths, estimated to be at least 900 meters, were calculated from gravity data taken during aerial surveys in 2000 and 2001. Because gravitational force is directly related to mass, a decrease in gravitational pull over the ice sheet corresponds to a decrease in mass beneath the ice. "Over the lakes, the pull of gravity is much weaker, so we know there must be a big hole down there," said Bell.

Their depth, along with the fact that they are parallel to each other and Lake Vostok, indicate that the lake system is tectonic in origin, the authors conclude.

Shallow lakes scooped out by glaciers or a meteorite impact can quickly fill with sediment, and thus are short lived. Lakes created by faulted blocks of the Earth's crust, however, are deeper and don't fill in as rapidly. Many of the smaller sub-glacial lakes scientists have identified so far are believed to be shallow "ephemeral" lakes that were suddenly sealed off by the ice.

The combination of heat from below and a thick layer of insulating ice above keeps the water temperature at the top of 90ºE and Sovetskaya at a balmy -2 degrees Celsius, despite temperatures on the surface that can drop to -80 degrees Celsius in winter. Since the lakes are bounded by faults, Bell said it is likely the lakes receive flows of nutrients that could support unique ecosystems. Moreover, laser mapping of the ice sheet surface by NASA's Ice Cloud and Land Elevation Satellite (ICESat) revealed that this water-ice boundary, or ceiling, is tilted.

"Since the surface is tilted, we know that the ice sheet changes thickness over the lake and that will drive circulation in the lake," said Bell. "This will provide mixing and distribute whatever nutrients are in the lake, which is an important component of subglacial ecosystems."

This, along with the tectonic origin of the lakes, supports the idea that despite climate changes on the surface over the last 10 million to 35 million years, the volume of the lakes have remained remarkably constant, providing a stable, if inhospitable, environment that may harbor an ancient and alien ecosystem adapted to life beneath the ice sheet. However, just how, when or even whether scientists will risk the possibility of contaminating the lakes to confirm their suspicions remains the subject of an ongoing international debate.

The study was supported by the Lamont-Doherty Earth Observatory, the Palisades Geophysical Institute, NASA, and the National Science Foundation.


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The Earth Institute at Columbia University is the world's leading academic center for the integrated study of the Earth, its environment and society. The Earth Institute builds upon excellence in the core disciplines--earth sciences, biological sciences, engineering sciences, social sciences and health sciences--and stresses cross-disciplinary approaches to complex problems. Through research, training and global partnerships, The Earth Institute mobilizes science and technology to advance sustainable development, while placing special emphasis on the needs of the world's poor. For more information, visit www.earth.columbia.edu.

The Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University, is one of the world's leading research centers seeking fundamental knowledge about the origin, evolution and future of the natural world. More than 200 research scientists study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean. From global climate change to earthquakes, volcanoes, nonrenewable resources, environmental hazards and beyond, Observatory scientists provide a rational basis for the difficult choices facing humankind in the planet's stewardship. For more information, visit www.ldeo.columbia.edu.

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Map Characterizes Active Lakes Below Antarctic Ice
http://www.sciencedaily.com/releases/20 ... 150949.htm

Dots represent the locations where scientists have identified 124 active lakes below the ice sheet in Antarctica. Warmer colors (orange and red) depict lakes with larger water volumes while cooler colors (green and blue) depict lakes with smaller volumes. Purple areas show the locations of previously known inactive lakes. (Credit: Ben Smith, University of Washington)

ScienceDaily (Sep. 2, 2009) — Lakes in Antarctica, concealed under miles of ice, require scientists to come up with creative ways to identify and analyze these hidden features. Now, researchers using space-based lasers on a NASA satellite have created the most comprehensive inventory of lakes that actively drain or fill under Antarctica's ice. They have revealed a continental plumbing system that is more dynamic than scientists thought.

"Even though Antarctica's ice sheet looks static, the more we watch it, the more we see there is activity going on there all the time," said Benjamin Smith of the University of Washington in Seattle, who led the study.

Unlike most lakes, Antarctic lakes are under pressure from the ice above. That pressure can push melt water from place to place like water in a squeezed balloon. The water moves under the ice in a broad, thin layer, but also through a linked cavity system. This flow can resupply other lakes near and far.

Understanding this plumbing is important, as it can lubricate glacier flow and send the ice speeding toward the ocean, where it can melt and contribute to sea level change. But figuring out what's happening beneath miles of ice is a challenge.

Researchers led by Smith analyzed 4.5 years of ice elevation data from NASA's Ice, Cloud and land Elevation satellite (ICESat) to create the most complete inventory to date of changes in the Antarctic plumbing system. The team has mapped the location of 124 active lakes, estimated how fast they drain or fill, and described the implications for lake and ice-sheet dynamics in the Journal of Glaciology.

What Lies Beneath

For decades, researchers flew ice-penetrating radar on airplanes to "see" below the ice and infer the presence of lakes. In the 1990s, researchers began to combine airborne- and satellite-based data to observe lake locations on a continent-wide scale.

Scientists have since established the existence of about 280 "subglacial" lakes, most located below the East Antarctic ice sheet. But those measurements were a snapshot in time, and the question remained as to whether lakes are static or dynamic features. Were they simply sitting there collecting water?

In 2006 Helen Fricker, a geophysicist at the Scripps Institution of Oceanography, La Jolla, Calif., used satellite data to first observe subglacial lakes on the move. Working on a project to map the outline of Antarctica's land mass, Fricker needed to differentiate floating ice from grounded ice. This time it was laser technology that was up to the task. Fricker used ICESat's Geoscience Laser Altimeter System and measured how long it took a pulse of laser light to bounce of the ice and return to the satellite, from which she could infer ice elevation. Repeating the measurement over a course of time revealed elevation changes.

Fricker noticed, however, a sudden dramatic elevation change -- over land. It turned out this elevation change was caused by the filling and draining of some of Antarctica's biggest lakes.

"Sub-ice-sheet hydrology is a whole new field that opened up through the discovery of lakes filling and draining on relatively short timescales and involving large volumes of water," said Robert Bindschadler, a glaciologist at NASA's Goddard Space Flight Center in Greenbelt, Md., who has used ICESat data in other studies of Antarctica. "ICESat gets the credit for enabling that discovery."

Networking in the Antarctic

But were active lakes under the ice a common occurrence or a fluke?

To find out, Ben Smith, Fricker and colleagues extended their elevation analysis to cover most of the Antarctic continent and 4.5 years of data from ICESat's Geoscience Laser Altimeter System (GLAS). By observing how ice sheet elevation changed between the two or three times the satellite flew over a section every year, researchers could determine which lakes were active. They also used the elevation changes and the properties of water and ice to estimate the volume change.

Only a few of the more than 200 previously identified lakes were confirmed active, implying that lakes in East Antarctica's high-density "Lakes District" are mostly inactive and do not contribute much to ice sheet changes.

Most of the 124 newly observed active lakes turned up in coastal areas, at the head of large drainage systems, which have the largest potential to contribute to sea level change.

"The survey identified quite a few more subglacial lakes, but the locations are the intriguing part," Bindschadler said. "The survey shows that most active subglacial lakes are located where the ice is moving fast, which implies a relationship."

Connections between lakes are apparent when one lake drains and another simultaneously fills. Some lakes were found to be connected to nearby lakes, likely through a network of subglacial tunnels. Others appeared to be linked to lakes hundreds of miles away.

The team found that the rate at which lake water drains and fills varies widely. Some lakes drained or filled for periods of three to four years in steady, rather than episodic, changes. But water flow rates beneath the ice sheet can also be as fast as small rivers and can rapidly supply a lubricating film beneath fast-flowing glaciers.

"Most places we looked show something happening on short timescales," Smith said. "It turns out that those are fairly typical examples of things that go on under the ice sheet and are happening all the time all over Antarctica."


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Adapted from materials provided by NASA/Goddard Space Flight Center.

 

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Antarctic lake home to diverse community of viruses
http://www.physorg.com/news177147268.html
November 11th, 2009 in Biology / Cell & Microbiology


Antarctic lake. Image credit: British Antarctica Survey.


(PhysOrg.com) -- A study of the genetic structure of viruses in an Antarctic lake has revealed an astonishing genetic richness in the large number of viral families discovered.

Aquatic viruses usually infect prokaryotes such as bacteria, but the viruses in the Antarctic had a large proportion of viruses that infect eukaryotes. The findings included small single stranded DNA (ssDNA) viruses and phycodnaviruses that have never previously been seen in aquatic environments.

The researchers, Alberto Lopez-Bueno and colleagues, from Spain and the UK, examined samples taken from Lake Limnopolar on Livingston Island in the Antarctic before and during the summer, and found the aquatic environment to be rich in microorganisms and a diverse collection of viruses that prey on them. The number of viral genotypes found was unusually high, running into thousands instead of the more usual hundreds, and less than 3 percent of the genome sequences were similar to previously identified viral genomes from aquatic systems. Many of the ssDNA viruses were related to non-aquatic viruses that infect plants, mammals and birds, and some had never been found in aquatic environments before.

The scientists also observed a change in the virus assemblage with the seasons. When the lake was covered in ice during spring, the smaller single strand DNA viruses dominated, while in summer, when the lake was open, the larger (>50 nanometer) double-stranded DNA viruses dominated, possibly because of seasonal differences in the host organisms, such as the algal blooms that appear in summer.

The scientists also found the double-stranded DNA viruses helped the bacteria survive by assisting their metabolism of amino acids and carbohydrates, and helping with respiration.

Antarctic lakes are covered with ice for around nine months of the year, and the underwater environment is cold, dark, and contains few nutrients, and is home to bacteria, protozoa, algae and viruses, and little else. In these conditions viruses probably play an important part in controlling the other microbes.

Viruses from Antarctica have been difficult to study in the past because they cannot be grown in the laboratory, but new genome sequencing technologies are allowing researchers to identify viruses without the need to grow them.

The research paper is published in the November issue of Science.

More information: High Diversity of the Viral Community from an Antarctic Lake, Science 6 November 2009: Vol. 326. no. 5954, pp. 858 - 861; DOI: 10.1126/science.1179287

 

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What lies beneath Antarctic ice
http://www.nature.com/news/2010/100903/ ... 0.442.html
Rodolfo del Valle and his team are heading to the Southern Ocean to measure a methane leak.

Ana Belluscio
Rodolfo del ValleFor three years, Rodolfo del Valle and his team will be probing the ice and seabed in the Erebus and Terror Gulf.

Persistent bubbling is stirring the water's surface in the Erebus and Terror Gulf, a remote spot off the Antarctic Peninsula. When he saw the commotion in 2000, Argentinian geologist Rodolfo del Valle was intrigued — despite 38 years' experience in the region. There was a chance the gas contained methane, and when del Valle's team investigated the leak they discovered it to be 99% methane.

This is bad news. The gas is not only 25 times more powerful than carbon dioxide at heating the atmosphere; methane hydrates locked up in the Antarctic seabed and ice also contain vast amounts of carbon — overall, methane deposits contain about half of global carbon. With a recorded decline in Antarctic ice shelves, the long-term effect of deteriorating and melting ice could range from boosting global warming to helping trigger mass extinctions. Nature caught up with del Valle on the eve of his departure for the first on-the-ground study to quantify methane leakage in shallow waters and ice in the Gulf.

What's the overall rationale for your upcoming three-year focus on methane hydrate deposits?

Statistics and figures aside, I have been participating in Antarctic expeditions for so long that I've seen entire ice shelves crumble into pieces small enough to prepare a Scotch on the rocks. We have had to redraw maps. Global warming is a fact, and once we quantify methane emissions we will have scientific proof that the substrate on the seabed is melting and leaking methane. If these methane deposits reach the atmosphere, they will deepen the greenhouse effect, which, in turn, will promote further methane release, thus closing the circle and ramping up warming.

A number of studies have pointed to methane as a factor in mass extinctions. Are we looking at the start of a similar scenario now?

By quantifying the emissions and establishing their magnitude, we will be able to begin to determine how they will affect global warming. We believe there is a huge amount of destabilized methane deposits that may leak into the atmosphere and ramp up warming. This is not a new fact in geological history. Of seven major mass extinctions that erased 90% of the species at the time, five are attributable to climate change, and one in particular — at the Permo-Triassic boundary — could be directly attributable to mass methane release in the Upper Palaeozoic.
crabeater sealsMethane could be implicated in deaths of crabeater seals in the area.Doug Allan / Nature Picture Library

Will you be investigating any direct consequences of methane leakage around the northern Antarctic peninsula?

The British Falkland Islands Dependencies Aerial Survey Expedition findings from the mid-1950s showed unusual numbers of crabeater seals dying in this area. Members of the expedition suggested that methane could be implicated. During the calving season, seals live and give birth on top of the frozen layer of sea, and dive for food through holes in the ice. One theory is that methane accumulates under the marine ice and escapes through cracks during low tides. The methane deposits located below the ice then expand. These emissions would be responsible for the massive death of seals: methane is usually accompanied by hydrogen sulphide, a toxic metabolite of methanogenic bacteria at the seabed. So we'll be looking at that in connection with the seal deaths.

Your investigation will focus on marine ice and shallow waters. Why shallow?

Working in waters less than 50 metres deep means seabed core samples are still frozen when they arrive at the sea surface for transport back to the lab for analysis. With frozen samples, we can determine the methane content of each ice layer. By looking at the ice crystals' structure, we can see possible freezing and thawing patterns of ice through ages. With crystals containing methane, we can tell how and when climatic variations occurred and their correlation with methane concentrations. All this will contribute to our knowledge of the nature of these deposits and the long-term climate change timeline through geological eras.

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Over the three years we're here, we will be able to monitor gases, determine the amounts escaping into the atmosphere during the seasons and ascertain any correlation with certain meteorological parameters such as pressure, winds and temperature to determine whether it's a massive escape — in which case effects on climate are far more likely.

Given the extreme weather conditions in Antarctica, how will your team coordinate the research in summer and winter?

Over the winters we will work on the ice shelf until the warm season arrives, when ice begins to fragment and is no longer safe to work on. At that moment, we will return to Argentina to analyse the information gathered in winter and prepare ourselves to return to work in summer, this time in expeditions on the water, when we'll collect gas samples from boats and explore the area with probes to locate the leaks.

 

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Yes, they will escape in the form of a virophage...

Virus-eating virus identified in Antarctic lake
http://www.physorg.com/news/2011-03-vir ... -lake.html
March 29th, 2011 in Biology / Cell & Microbiology

(PhysOrg.com) -- Deep within the waters of Antarctica's Organic Lake an Australian research team, led by microbiologist Ricardo Cavicchioli from the University of New South Wales, have discovered a new virophage, or virus eater. Their findings were recently published in the Proceedings of the National Academies of Sciences.

The new virophage was discovered by graduate student Sheree Yau and given the name Organic Lake Virophage, or OLV. The new virophage was identified when she noticed that sequences in the protein shell from the lake were similar to a previously discovered virophage named Sputnik.

Sputnik, which was first discovered in the water-cooling tower in Paris in 2008, was the first virophage ever identified. Earlier this month, Matthias Fischer and Curtis Suttle announced the discovery of a second virophage known as Mavirus.

The discovery of OLV makes this only the third virophage, though there is evidence of sequence matches to OLV in numerous other locations including the nearby Ace Lake. However, the other matches span the globe, including a lagoon in the Galapagos Islands, a bay in New Jersey, and a freshwater lake in Panama.

Virophages, which are known as virus eaters, attack other viruses, as is the case with the first virophage, Sputnik. Unable to multiply within a host, virophages rely on hosts infected with other viruses. In the case of Sputnik, it was an amoeba infected with a mamavirus. Sputnik would essentially take over the replication process of the mamavirus. Because of this takeover, the mamavirus is unable to produce properly, thus reducing its ability to infect the amoeba.

The new OLV genome was discovered within the sequences of phycodnaviruses. Phycodnaviruses are a group of large viruses that attack algae. The OLV targets these phycodnaviruses, allowing the algae in the lake to survive and bloom during the summer months.

The team’s discovery, and the discovery of connected sequences in other locations around the globe, opens the door for the possible discovery of many more virophages. The study of these virus eaters is just beginning and holds promise of a better understanding of the complexity of biological function within these viruses.

More information: Sheree Yau et al., Virophage control of antarctic algal host–virus dynamics, Published online before print March 28, 2011, Proceedings of the National Academies of Sciences doi:10.1073/pnas.1018221108

 

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And the ice is thicker than was previously thought. Vids at link.

A new type of 3D mapping revealed Antarctic sea ice could be much thicker than previously estimated, shows a study done with the help of a yellow robotic submarine named SeaBed.

The new study, published in Nature Geoscience, showed that average ice thickness in Antarctica is between 1.4 meters and 5.5 meters. The maximum thickness recorded was 17 meters.

Also, 76 percent of the mapped ice has been tagged as ‘deformed,’ the study stated, which means that ice crashed together, forming a thicker layers of ice. ...

http://rt.com/news/208503-antarctica-thicker-sea-ice/