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An international research team will head to the high
plateau in East Antarctica to probe subglacial feature
with cutting-edge instruments
By Peter Rejcek, Antarctic Sun Editor
A mountain range the size of the European Alps, but buried
below hundreds of meters of ice and snow, has puzzled
and enticed Antarctic scientists since its discovery 50
years ago.
How did it get there? What does it look like? How tall
is it? What role did it play in the formation of the ice
sheet?
Those are a few of the questions an international team
of researchers will attempt to answer beginning this season,
as they venture into the Antarctic Gamburstev Province
(AGAP), a high-altitude region in East Antarctica.
“We don’t know why that mountain range is there.
It’s really a mystery,” said Robin Bell, a principal
investigator for AGAP’s aerogeophysical component,
nicknamed GAMBIT. “It’s kind of like finding
a mountain range in the middle of Canada.”
A Soviet overland traverse discovered the Gamburtsev
subglacial range during the International Geophysical
Year in 1958. Scant other data exist aside from a few
aerogeophysical surveys dating back to the 1970s.
A multi-nation effort to study the subglacial mountain
range in more detail came together as a result of the
International Polar Year (IPY). U.S. investigators are
teaming with scientists from the United Kingdom, Germany,
China, France, Italy, Japan and Australia to tackle a
place that is logistically tough to work alone.
“A project of this size, really, can only happen
in the framework of IPY because it requires so many people
to support a project of this magnitude,” noted Michael
Studinger, co-principal investigator for GAMBIT. Both
Studinger and Bell are researchers at Lamont-Doherty Earth
Observatory of Columbia University in New York.
AGAP is the flagship of the U.S. IPY program, said Tom
Wagner, program director of Earth Sciences in the Office
of Polar Programs at the National Science Foundation (NSF).
“It truly pushes the frontiers of science by telling
us more about Antarctica’s geologic history, but
it also has profound implications for ice sheet models,”
he said.
GAMSEIS
The science campaign to discover the nature and origin
of the range includes three field seasons to install and
retrieve 25 seismic stations around the Gamburstev Province.
Doug Wiens of Washington University in St. Louis heads
up this end of the project, dubbed GAMSEIS.
Wiens said a six-member field team plans to install 10
seismographs this season and 15 next year. The instruments
will provide information on the structure of the mantle
and crust beneath the mountains to learn more about the
history of the subglacial range.
“The basic question is: What’s holding them
up? What’s causing the high elevations there?”
he explained. “That’s related to the issue of
how old the mountains are, which is really important for
reconstructions of the climate of Antarctica in the past,
and even the whole world.”
France, China and Japan all have plans to install additional
seismic stations as part of the effort, which encompasses
an area about 1,000,000 square kilometers. The Chinese,
working out of Zhongshan Station, will conduct a traverse
that includes setting up a seismograph at Dome A, a plateau
about 1,200 kilometers inland and more than 4,000 meters
above sea level.
The Italians and Australians may also participate, Wiens
said, but are waiting for funding to materialize.
The American scientists will establish a field camp near
Dome A, but closer to 3,500 meters in altitude. They will
use a Twin Otter aircraft to carry people and equipment
to the 10 seismic sites, hoping to knock out two each
day.
The work is not without its challenges. “We’ve
rarely worked at elevations this high and cold, and [Raytheon
Polar Services] has made a major effort in planning for
this project with multiple camps and complex acclimatization
schedules to accomplish it safely,” Wagner noted.
The GAMSEIS network will operate in concert with another
IPY project, POLENET, which seeks to install high-precision
GPS and seismic instruments on nearly every exposed rock
in West Antarctica and the Transantarctic Mountains.
One of the main goals of that project is to measure the
rate of terrestrial rebound from the loss of ice in West
Antarctica since the last glacial maxim 20,000 years ago,
when there was much more ice there than today. That will
help scientists more precisely determine ice mass and
create better models to predict sea level rise in a global
warming scenario.
“Also, the GAMSEIS data will be combined with POLENET
data to give us a more complete view of the earth’s
interior from the Antarctic crust all of the way to the
core,” Wagner said.
GAMBIT
The heavily supported geophysical air campaign will begin
next season in 2008.
The current plan is to fly two Twin Otter aircraft for
nearly 20 hours per day out of one or two field camps
located near Dome A. The U.S. Antarctic Program (USAP)
will provide one plane, with the British Antarctic Survey
pledging a second aircraft.
“This would give us more flexibility in designing
the survey and covering a larger area over the Gamburstev
Subglacial Mountains,” Studinger said.
Earlier this year, GAMBIT scientists tested the concept
with a Twin Otter carrying two new gravimeters on a flight
from Ellesmere Island, Canada, to the North Pole and back.
“The test flights went very well,” Studinger
said. “Next year we plan to install the complete
system consisting of radar, laser, gravimeter and magnetometer
systems for the first time.” Tests will follow in
Calgary and Greenland.
If all goes well, the scientists will install the same
system at McMurdo Station before heading into the field.
“We will probably fly about four weeks, 20 hours
a day, assuming the weather is fine,” Studinger said.
With the Americans and British covering the air and the
ground, the Chinese will head down into the ice and rock
itself.
“The Chinese want to select an ideal drill site
for ice-core drilling,” Studinger explained. “This
is something they plan to do in subsequent years. This
ice core drilling will also recover a bedrock sample in
a handful of years.”
The hypotheses
Hypotheses for the mountain range’s origin are fairly
sketchy at this point due to the lack of data. One theory
says the mountains are hot-spot volcanoes that came up
through the crust. “We don’t think so, but that’s
one hypothesis on the table,” Bell said.
Another idea is that the mountains represent an area
of high topography, protected from erosion by a layer
of rocks relatively tough, weather-resistant rocks.
“What’s really surprising is that the mountains
are there,” Studinger noted, explaining that the
Gamburstevs appear circular, an interior continental feature
difficult to explain by plate tectonics.
Wiens said most researchers believe the mountains are
much older than what the “hot spot” theory would
allow — an age of tens of millions of years, versus
hundreds of millions of years. Rocks found at the coast
are at least 500 million years old, he said.
“By extrapolation, then, people think that probably
the rocks in the middle of the continent are very old,”
he explained. “But nobody really knows.”
Each measurement will give the scientists different clues
as they puzzle out the origins of the subglacial range
and its larger role in the continent’s history. Ice-penetrating
radar, for example, will give them details on ice thickness
and layering above the Gamburstevs. Other instruments
will provide details on the gravity field, which indicates
the type of rocks that are present.
“We have to compare these data to other existing
features on the Earth, which we can, and usually we can
exclude some models or some ideas and narrow it down to
one or two in the end,” Studinger said.
AGAP will make use of brand new tools in the venture,
according to Wagner. Seismometers with ultra-cold rated
motors were developed just for this project. The ice-penetrating
radar is the latest design from the Center for the Remote
Sensing of Ice Sheets at Kansas University, an NSF-funded
Science and Technology Center.
More mystery
The region where the subglacial mountain range sits holds
other prizes for science.
“One of the science-drivers behind the survey is
not only the geologic origin of the Gamburstev Subglacial
Mountains, but also the science community is very convinced
that this region in Antarctica … is where people
hope to find the oldest ice,” Studinger explained.
“It would be one of the really important outcomes
to locate the region with the oldest ice,” he added.
The educated guess is that the ice is at least 1.5 million
years old. A low snow accumulation rate combined with
a slow-moving ice sheet gives scientists reason to believe
this.
The researchers also think the Gamburstevs were the nucleation
point for the East Antarctic ice sheet, which formed more
than 30 million years ago.
Adding to the mystery: “We don’t even know
if the mountains were there 35 million years ago,”
Studinger said.
Said NSF’s Wagner, “Because of their height
and location, the Gamburtsevs are where the ice sheets
start according to our best models. That’s why understanding
when they formed — before or after the ice sheets
— and characterizing their topography is so important.”
“If you want to put East Antarctica into the global
plate tectonic framework, you have to understand the tectonic
evolution through time in this region,” Studinger
added.
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Antarctic
Sun
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