Antarctica's ground zero
Expedition heads to Pine Island Glacier region to study thinning ice shelf
Posted December 23, 2011
Bob Bindschadler doesn’t want to spend the holidays — or, really, any day of the year — on the small, crevasse-riddled ice shelf in West Antarctica that catches all of the ice from the fast-flowing Pine Island Glacier.
But it’s on that floating bed of ice — well, more accurately, 500 meters below where it meets the water — where Bindschadler and his colleagues believe they’ll learn important lessons about how the ocean and ice grapple. It’s where warm water, drawn up onto the continental shelf from deep ocean depths by atmospheric winds, is eating away at the shelf — thinning the ice — and allowing the glacier upstream to move ever faster.
For the glaciologist from NASA, this is ground zero for research into how Antarctica will contribute to future sea-level rise.
“The urgency of getting the science done is … unique to the other places I’ve been. Never in my life would I choose to go and work here. But the secrets to ice sheet stability, I am certain, lie underneath this ice shelf,” said Bindschadler, emeritus scientist at NASA’s Goddard Space Flight Center.
A veteran of some 15 polar expeditions, Bindschadler will lead more than a dozen investigators to the ice shelf over December and January. The plan is to use a hotwater drill to bore through 500 meters of ice. They’ll then deploy instruments through the hole to measure what the researchers refer to as the “ocean-ice interaction.”
The Pine Island Glacier (PIG) Ice Shelf program — funded and supported by the National Science Foundation (NSF), NASA and the British Antarctic Survey (BAS) — is one of those projects where “easier said than done” truly applies.
The weather along coastal West Antarctica is simply atrocious, punctuated by gale-force winds and whiteout conditions, with occasional days of stunning blue skies. The ice shelf itself is pockmarked with crevasses, like an old face that had been ravaged by acne.
In fact, the surface of the ice shelf is so nasty that when Bindschadler and colleague David Holland with New York University landed there during the 2007-08 Antarctic field season on a Twin Otter, a plane that uses skis for landing gear, the pilots decided they couldn’t safely do it again.
Long road back
It’s taken four years and a herculean logistics effort to set the stage for this year’s attempt to land on the ice shelf using helicopters, which will be based at a main camp located about 80 kilometers away on the West Antarctic Ice Sheet. But to install that camp, a second camp farther inland called Byrd Surface Camp — a site with a long history in the U.S. Antarctic Program — first had to be built.
But the scientists and camp staff in McMurdo Station awaiting transport to the PIG main camp are already living the lesson that they know so well — weather trumps all in Antarctica. As of Dec. 18, about three weeks after the first LC-130 aircraft was to make the 11-hour roundtrip journey, not one of the 14 planes scheduled to support the camp had been able to land at the site.
“We don’t know what to expect until we get out there,” said Charles Kirkland, who will be in charge of the camp personnel who will support the research team working on the ice shelf.
Kirkland is no stranger to the frustrations and hardships of working in Antarctica’s hinterland. He’s spent all of his six of his seasons with the USAP in the deep field, first as a camp medic and later as camp manager for projects in both West and East Antarctica, including three months at an elevation of nearly 4,000 meters where scientists mapped an Alps-sized mountain range under the ice.
“I do the deep field. I like the deep field,” said Kirkland, a man of obvious kinetic energy, whose 11-person team must be able to handle not just bad weather, but mechanical breakdowns and weeks of isolation with only each other to depend upon.
“We’re looking for utility players in the deep field. Nobody has one job,” Kirkland explained.
Day after day, he and his staff of mechanics, meteorologists, cooks and others take the news in stride — another weather cancelation. A team of carpenters will also fly out on the first few flights to help put the camp together.
“I figure my weather windows are going to be far and few between, so I want to get buildings up as fast as possible,” Kirkland said. “The weather if fifty-fifty there. We’ll have four days of [foul weather] and five days of knockdown gorgeous weather, and we’re going to [work extremely hard] on those days.”
Window on the weather
Holland, the climate scientist from NYU, has been a victim of West Antarctic weather in the past, spending weeks sipping hot chocolate and not doing much else while stuck at Byrd field camp.
“It would snow so much that we would have a meal and four hours later the door [to the galley] would be snowed in,” he said. “It was a lot of work getting in and out.”
But Holland did finally get out, completing his mission last season to install three weather stations around the Pine Island Bay region that will provide important data about the atmospheric conditions that influence the ocean currents.
“The idea is that we’re trying to correlate atmospheric and oceanographic observations to see what is causing the PIG [to recede],” explained Holland, who returned to McMurdo Station this season on a pilot project to test a different technology for observing the ocean-ice interaction.
The PIG story actually starts in the atmosphere, where clockwise winds, the “westerlies,” around Antarctica have intensified in recent years.
Two camps have emerged about why that’s happening. One group blames the ozone hole over Antarctica, which has cooled the stratosphere over the continent while rest of the planet has warmed. That temperature differential has spun up the winds, they believe. An emerging, alternative hypothesis blames atmospheric influences from the tropics for strengthening the west winds.
The “why” of the atmosphere problem is less important to the PIG researchers than the “what” — what is happening in the ocean as the winds intensify? The leading theory, which Holland’s triangle of weather observatories will help confirm, is that winds are pushing surface waters away from the continent, which draws a current of deeper, warmer water up onto the continental shelf and under the ice.
“We hope the triangle at Pine Island Bay is a proxy for the bigger scale winds,” Holland said.
An emerging picture
Now it’s up to Bindschadler and his team of oceanographers, glaciologists, and the other members of the multidisciplinary group to get the ocean measurements from underneath the ice shelf. But they’re not going in totally blind.
Several airborne and ship-based expeditions to the area in the last several years have provided vital details about features both on and below the ice shelf. New high-resolution satellite imagery from the NSF-funded Polar Geospatial Center (PGC) has also sharpened the picture.
One of the key pieces of information to emerge a couple of years ago came from a joint U.S.-British expedition aboard the USAP research vessel Nathaniel B. Palmer. The BAS scientists sent a robotic submarine underneath the ice shelf, the first-ever such deployment beneath this ice shelf.
The so-called Autosub mapped the bathymetry, or seafloor topography, underneath a large part of the ice shelf cavity in great detail. It also, quite literally, hit upon a new discovery — a ridge that rose about 350 meters from the seafloor to within about 150 meters of the ice shelf. That find was a game-changer for the PIG researchers, according to Bindschadler.
“That was a huge surprise to us. We thought we’d be able to drill any place out there,” he said during an interview at McMurdo, anxiously waiting for the first flight to leave, the expedition’s window of time in the field shrinking daily. “The discovery of that ridge caused us to totally revise our thinking about where we were going to put our profilers.”
The profiler carries instruments along a cable that will measure temperature, salinity and the current. The cable will extend all the way from the surface of the shelf, through roughly 500 meters of ice, and down through the water column, which is about 500 meters deep.
Here’s the problem: The weighted cable, if installed “upstream” of the seafloor feature, would have been dangling too far down and would have become fouled on the ridge, as the motion of the ice shelf carried the cable at the glacially breakneck speed of 18 inches per hour.
NASA’s ongoing IceBridge campaign to observe changes in West Antarctica provided an additional detail about what the cavity looks like below the ice shelf. Data from gravity instruments flown aboard a NASA plane that doubles as a research lab suggest that the ridge doesn’t cross the width of the ice shelf. An open channel appears to exist to the west, where the warm water might freely flow around the ridge.
Peaks and valleys
Finally, last year, BAS scientists flew a Twin Otter with their own radar instruments across parts of the ice shelf. The tight grid lines flown by pilots — called “mowing the lawn” — revealed that the bottom of the ice shelf isn’t being cleanly planed off by the warm water. Instead, the bottom more closely resembles corrugated steel, where channels have been carved.
That ocean action affects not just the bottom of the ice shelf, but also the surface, Bindschadler explained. The channeling below creates an inverse effect on top, causing small ridges to form longitudinally between where two channels exist on the bottom of the ice shelf.
Each surface ridge, heavily crevassed by the flexing, is next to a narrow valley that appears free of cracks. Mirroring each surface valley below the ice shelf is one of the channels carved by the warm water.
“It’s really nice that the one place where we can work, which is in the valleys, is sitting right over the top of where that meltwater is being concentrated by the topography of the bottom of the ice shelf,” Bindschadler said. “That’s the water we want to see. We get lucky. That’s where we can work and that’s where we want to work.”
But it’s not a lot of room to work. Each valley is only a few hundred meters wide, but enough to establish the drill camp and all of the associated equipment, which must be moved by helicopter.
The helos will also be used to ferry glaciologist Sridhar Anandakrishnan from Pennsylvania State University around the ice shelf. Anandakrishnan is an expert in using a technique called reflection seismology, which uses seismic waves, or waves of energy generated from something like an earthquake or explosion, to learn about the properties of the Earth’s subsurface. In this case, the technique will reveal the shape of the ocean cavity, the properties of the bedrock under the ice shelf and the layers of ocean sediment draped on that bedrock.
The researchers plan to install three profilers between this year and next. The instruments were developed by co-principal investigator Tim Stanton and his team at the Ocean Turbulence Laboratory in the Oceanography Department at the Naval Postgraduate School. The technology was first used in the Arctic.
Each installation should take a about a week, Bindschadler said, based on a test run of the system two years ago near McMurdo Station on the nearby ice shelf. The team hopes it can deploy two profiler systems this year, but the ongoing transportation delays are jeopardizing that plan.
“The hardest part we always knew would be getting out to PIG,” said Bindschadler, whose patience seems to be matched only by his desire to capture the data that he has been chasing for years.
Time may be short for the expedition. But based on the rates of melting under way in parts of Antarctica and Greenland, the world may be running out of time before catastrophic sea-level rise begins. Many scientists now believe global oceans will likely rise by a meter by the end of the century — but the uncertainties are still too great to predict the future properly.
“Melting ice holds the greatest possibility for change, and that’s why we’re interested in it,” Holland said. “Many cities around the world would be affected by sea-level change.”
NSF-funded research in this story: Robert Bindschadler and Alberto Behar, Goddard Space Flight Center, Award No. 0732906; Tim Stanton, Naval Postgraduate School, Award No. 0732926; David Holland, New York University, Award No. 0732869; Sridhar Anandakrishnan, Penn State University, Award No. 0732844; Miles McPhee, McPhee Research Company, Award No. 0732804; and Martin Truffer, University of Alaska, Fairbanks, Award No. 0732730.