Andrew Yee
January 31st 06, 04:20 PM
Lamont-Doherty Earth Observatory
The Earth Institute at Columbia University
New York
Contact:
Ken Kostel, (212) 854-9729
01/25/06
Two New Lakes Found Beneath Antarctic Ice Sheet
Ancient water bodies may contain ecosystems adapted to life beneath more
than two miles of ice
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 90šE 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 90šE 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 90šE 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.
The Lamont-Doherty Earth Observatory, a member of The Earth Institute at
Columbia University, is one of the world's leading research centers
examining the planet from its core to its atmosphere, across every
continent and every ocean. From global climate change to earthquakes,
volcanoes, environmental hazards and beyond, Observatory scientists
provide the basic knowledge of Earth systems needed to inform the future
health and habitability of our planet.
The Earth Institute at Columbia University is among the world's leading
academic centers for the integrated study of 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 its research training and global
partnerships, it mobilizes science and technology to advance sustainable
development, while placing special emphasis on the needs of the world's
poor.
For more information, visit
http://www.ldeo.columbia.edu
IMAGE CAPTIONS:
[Figure 1:
http://www.ldeo.columbia.edu/news/2006/images/antarctica012606.jpg (68KB)]
MODIS satellite image showing location of Sovetskaya Antarctic research
station and 90šE Lake in relation to Lake Vostok. Detail of area in the
white box is shown in Figure 2.
[Figure 2:
http://www.ldeo.columbia.edu/news/2006/images/antarctica012606b.jpg
(67KB)]
Detail of ice surface revealing outline of 90šE lake (center) and part of
Sovetskaya Lake (beneath Sovetskaya research station). Data from 1958
Soviet study (colored dots) revealed a noticeable drop in the Earth's
gravitational pull above the two lakes. White triangles mark the locations
of smaller lakes beneath the ice.
The Earth Institute at Columbia University
New York
Contact:
Ken Kostel, (212) 854-9729
01/25/06
Two New Lakes Found Beneath Antarctic Ice Sheet
Ancient water bodies may contain ecosystems adapted to life beneath more
than two miles of ice
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 90šE 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 90šE 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 90šE 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.
The Lamont-Doherty Earth Observatory, a member of The Earth Institute at
Columbia University, is one of the world's leading research centers
examining the planet from its core to its atmosphere, across every
continent and every ocean. From global climate change to earthquakes,
volcanoes, environmental hazards and beyond, Observatory scientists
provide the basic knowledge of Earth systems needed to inform the future
health and habitability of our planet.
The Earth Institute at Columbia University is among the world's leading
academic centers for the integrated study of 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 its research training and global
partnerships, it mobilizes science and technology to advance sustainable
development, while placing special emphasis on the needs of the world's
poor.
For more information, visit
http://www.ldeo.columbia.edu
IMAGE CAPTIONS:
[Figure 1:
http://www.ldeo.columbia.edu/news/2006/images/antarctica012606.jpg (68KB)]
MODIS satellite image showing location of Sovetskaya Antarctic research
station and 90šE Lake in relation to Lake Vostok. Detail of area in the
white box is shown in Figure 2.
[Figure 2:
http://www.ldeo.columbia.edu/news/2006/images/antarctica012606b.jpg
(67KB)]
Detail of ice surface revealing outline of 90šE lake (center) and part of
Sovetskaya Lake (beneath Sovetskaya research station). Data from 1958
Soviet study (colored dots) revealed a noticeable drop in the Earth's
gravitational pull above the two lakes. White triangles mark the locations
of smaller lakes beneath the ice.