|
By Peter Rejcek
The 12 scientists and support staff who made a slow crawl
across a vast, blank stretch of East Antarctica this past
austral summer for three months to study how regional
climate variability relates to global climate change expected
to encounter brutally cold storms and other challenges
on the high polar plateau.
They didn’t expect to come across other travelers
in the relatively unexplored area known as Queen Maud
Land. But they did — three times in one day.
“We were astonished because we were supposed to
be all alone,” said Ted Scambos , a member of the
Norwegian-U.S. science team that crossed a large slice
of the Antarctic continent using tracked vehicles pulling
sleds. “I don’t know where you can go in order
to be on the edge of the Earth anymore.”
The encounters, all involving people taking part in a
commercial race to the South Pole, occurred near a fuel
depot in an area where the ice sheet was more than 3,000
meters thick, hiding at least four distinct subglacial
bodies of water called the Recovery Lakes.
“Fuel depots in Antarctica are kind of the equivalent
of watering holes in Africa,” mused Scambos, lead
scientist at the Boulder, Colo.-based National Snow and
Ice Data Center . “Everybody has to come to the fuel
depot, and you see all kinds of people, all kinds of groups,
gathered at the fuel depot.”
But for most of the roundtrip journey between Norway’s
Troll research station on the coast and the U.S. Antarctic
Program’s South Pole Station , the scientists and
crew were on their own. They took measurements of the
snow and ice in areas that virtually no one had visited
since the late 1960s, when the United States primarily
used tractor trains to conduct deep-field science work.
Living and working out of bright red, boxed buildings
mounted on sleds, the team collected ice cores at various
depths and locations, used radar to map the ice sheet
layers and dug snow pits — all in an effort to understand
the climate in this area for the last thousand years and
how it may be changing today. The project was part of
the International Polar Year , a 60-nation effort to better
understand the Antarctic and Arctic, which officially
ended last month.
“It’s really been a blank spot on the map —
on both the literal map as well as the metaphoric map
of climate change in Antarctica,” said Tom Neumann
, leader of the traverse team during the second leg of
the two-year project that began in 2007-08 and covered
nearly 7,000 kilometers including a few side trips. “[The
traverse] should help fill in the picture of how Antarctica
overall is changing.”
The traverse team attempts to recover a stuck ice core
drill, which they later did.[See related story: Norway,
U.S. team up for IPY traverse]
Scientists had believed that Antarctica was largely bucking
the global warming trend. While West Antarctica was undoubtedly
heating up — particularly the outstretched tip of
the Antarctic Peninsula where ice shelves are disappearing
at historic rates — studies of the much larger East
Antarctic Ice Sheet suggested a cooling trend.
Some researchers have suggested the depletion of stratospheric
ozone over Antarctica — the ozone hole that appears
each austral spring — is affecting atmospheric circulation
and westerly winds around the continent, effectively shielding
it from global warming. But a paper in the journal Nature
earlier this year said warming in West Antarctica is greater
than whatever cooling may be occurring on the rest of
the ice-covered continent.
“Simple explanations don’t capture the complexity
of climate,” explained Eric Steig , lead author of
the Nature paper and a professor at the University of
Washington , in a statement back in January.
“The thing you hear all the time is that Antarctica
is cooling, and that’s not the case,” added
Steig, a collaborator on the IPY traverse project. “If
anything it’s the reverse, but it’s more complex
than that. Antarctica isn’t warming at the same rate
everywhere, and while some areas have been cooling for
a long time, the evidence shows the continent as a whole
is getting warmer.”
Antarctica is roughly the size of the United States and
Mexico: Snow in Denver doesn’t mean a blizzard stretches
all the way down to Mexico City. “Antarctica is a
huge place, and I would be surprised if it was all doing
the same thing,” said Neumann, a scientist now with
NASA Goddard Space Flight Center .
Yet there’s even a hint that East Antarctica —
well, at least one spot on that incomplete map —
may be warming based on one initial experiment by the
traverse team. Scambos deployed strings of highly sensitive
“thermometers” called thermistors into two of
the deeper ice core holes.
The temperature on the ice sheet surface changes with
the weather, but the temperature deeper down changes very
slowly as the climate changes. Neumann likens it to throwing
a frozen turkey into the oven — not the best way
to cook a turkey, for sure, but eventually the center
starts to thaw and cook based on the long-term outside
temperature.
“It takes a while for the ice at 90 meters to notice
how the surface temperature has changed,” Neumann
explained. At that depth, the ice temperature is determined
by the average temperature of the last 50 years or so.
The instruments will operate for the next several years,
allowing the scientists to determine how surface temperature
changes through time.
“The initial results do say these areas are warming,”
Neumann said, stressing that the measurements are in the
hundredths of a degree per year and the data still raw.
Scambos: Recovery Lakes region was likely marine embayment
in distant past
Most of the scientific analysis is yet to come. Neumann
and others on the team will use the ice core samples to
conduct stable isotopic measurements. By studying the
isotopic ratios of oxygen 16 and oxygen 18, for instance,
researchers can figure out what the climate was doing
at a particular time because different ratios indicate
different types of climate.
The chemistry will help the team calibrate the radar
returns of the ice layers, a key step to nailing the snow
accumulation rates in East Antarctica — one part
of the equation to whether the ice sheet is overall losing
or gaining mass. Loss of mass would indicate a rise in
sea level.
“The chemistry from the core helps because it tells
you the accumulation rate at a point,” Neumann explained.
“For example, how deep is the fallout from the 1960s
above-ground nuclear testing? That information helps to
calibrate the radar layers that intersect the core site.
“If a radar layer is shallower, then it has had
relatively less accumulation; a deep layer reflects relatively
more accumulation. The information form the core lets
you quantify the ‘relative’ statements above.”
The scientists also took the opportunity to explore the
Recovery Lakes, an area of at least four lakes at the
head of one of the largest ice streams draining East Antarctica.
Ranging in size from 600 to 1,500 square kilometers, at
depths well below sea level, the lakes were likely part
of a deep marine embayment millions of years ago when
the ice sheet was much smaller, according to Scambos.
“It was probably dynamic in the past,” he said.
“In the distant future, if the Earth gets a great
deal warmer, it would be dynamic again. I would prefer
to think that we’ll stabilize climate change before
we have to worry about this part of Antarctica disintegrating.”
There is still a lot of uncertainty about what the Antarctic
ice sheets may do in the future because so little of it
has been measured, particularly compared to Greenland,
according to Neumann.
“The uncertainties in Greenland are getting quite
a lot smaller as we get more and more data about ice velocity,
ice thickness and accumulation rate. It’s certainly
negative [mass balance] and we know roughly how negative
it is in Greenland,” he said. “Antarctica is
a bit of a different story, because it is so much larger
and there’s places with so much less data, such as
in East Antarctica.
“The physical insight is coming along and the model
development is coming along, but I think it’s going
to be a quite a while before we really have confidence
in the large-scale predictive models of ice sheet change,”
he added.
More ground-based studies like the traverse would help
to continue filling in the blank spots of the climate
change map, according to the scientists. “Most of
that uncertainty [about Antarctica] can be beaten down
with more and more measurements of accumulation rates,”
Neumann said.
“The traverse system that the Norwegians have put
together is fantastic, state-of-the-art. It’s the
best in the world right now in terms of supporting a science
crew over long distances,” Scambos said. “They
essentially have a mobile, 12-person base that provides
them relatively easy access to a large area. … [Queen
Maud Land is] one of the least-explored areas of Antarctica,
and I think that’s going to change, in part, thanks
to this traverse system they’ve got.”
-
Antarctic
Sun -
|
