|
By Peter Rejcek, Antarctic Sun Editor
Scientist Bob Bindschadler’s choice for a place
to conduct research in West Antarctica shares some of
the same criteria as those of his colleagues fanning out
across Antarctica for the International Polar Year (IPY).
“It’s a hard place to get to. It’s a terrible
place to work,” he says of the crevasse-ridden Pine
Island ice shelf, adjacent to the West Antarctic Ice Sheet
(WAIS), where he will work this season.
But the possible scientific payoff is also IPY worthy,
considering the question he hopes to answer: “How
is the ocean tickling the ice sheet and why is the ice
sheet responding so dramatically?”
The objective is to study the interaction of the ocean
and the fast-moving glacial ice of Pine Island Glacier.
Bindschadler and his colleagues believe that, based on
satellite imagery, warm, salty ocean water is a key component
chipping away at the edges of the continent’s ice
sheets and quickening the pace by which glaciers dump
ice into the ocean.
“The signature from those [satellite] observations
is pretty clear: that the changes are largest at the perimeter
of the ice sheet and decrease in magnitude as you go inland,”
he explained. “That says to us that the trigger,
the driver of these changes, is the ocean.”
Chief scientist with the Hydrospheric and Biospheric
Sciences Laboratory at NASA’s Goddard Space Flight
Center, Bindschadler said that until recently the technology
wasn’t available to make the sort of measurements
scientists need to model ice and ocean interaction below
the ice sheet.
Those models are important in predicting how WAIS will
react to climate change as global warming ratchets up
ambient and ocean temperatures. Conservative estimates
predict the ice sheet, if it were to disintegrate completely,
would raise sea level by five meters.
Reconnaissance mission
But before anything can happen, the researchers must determine
if they can even go to work. The site they’ve chosen
is a dynamic area home to the two, fastest-moving glaciers
on the continent – Pine Island and Thwaites glaciers,
both of which pour into the Amundsen Sea.
“Job one is to land and survive,” Bindschadler
said. He has identified one area where he believes a Twin
Otter can safely land and where he and colleague David
Holland from NYU can make some basic measurements.
The site is about 35 kilometers from the calving edge
of the 800-square-kilometer ice shelf. That’s close
to where they expect to find the grounding line, where
the warm dense ocean water hits the ice in contact with
the bedrock.
“We’re pretty sure that’s where the melt
rates are the highest and where these key processes are
most intense,” Bindschadler said.
The idea is to pack light for this visit. The scientists
will set up an automatic weather station to beam back
climate data through the austral winter. Meteorologists
are also interested in the information, as the area represents
one of the biggest weather gaps on the planet, according
to Bindschadler.
They will also set up two GPS receivers to determine
ice velocity and ocean tides. The latter measurement will
indicate how much flex the ice shelves are experiencing.
Two British field researchers, working farther upstream
on the glacier, will spend a week at the Americans’
camp and use ice-penetrating radar to measure the ice
thickness and, more importantly, changes in the thickness.
A second, nearby research team will visit with seismic
equipment to measure the depth of the water. “That’s
something we want to know because that’s critical
for setting up next year’s sub-ice instrumentation
and for modeling the water circulation underneath the
ice shelf,” Bindschadler said.
Looking below
If all goes as planned, work would begin in earnest the
next two field seasons to use a hot water drill to bore
through the 500-meter-thick ice and lower instruments
into the ocean cavity below.
A video camera is among instrument the scientists will
send down the borehole. What does the ice underneath look
like? Is it smooth? Is it rough? No one knows, Bindschadler
said.
They will also deploy small, oceanographic profilers
through the 13-centimeter-wide hole. The profiler will
continuously run up and down a cable measuring current,
temperature and salinity, transmitting the information
up a cable frozen into the borehole to an Inmarsat terminal
that beams the data to a satellite.
It’s an exciting study, according to Kelly Falkner,
program manager of the newly created Antarctic Integrated
System Sciences (AISS) department in the Office of Polar
Programs at the National Science Foundation. AISS and
NASA are co-funding the project.
“That will be the first direct set of observations
beneath an ice shelf like this that extend throughout
the year,” she said.
Eventually, the research team hopes to bore several holes
over the two field seasons to characterize the horizontal
currents, another important factor for modeling the interaction
between ocean and ice.
This is an example of the sort of science that IPY supports:
lots of unknowns with big potential for discovery. How
deep will the water be? Will the profiler work? It’s
been used in the Arctic, where the ice is only a few meters
thick.
“There’s a lot of unknown and a bit of finesse,
but these scientific questions must be answered. We have
no choice but to try and get the answers,” Bindschadler
said.
-
Antarctic
Sun
|
