The Antarctic Sun - Science Section United States Antarctic Program United States Antarctic Program Logo National Science Foundation Logo
 

Changing course

LARISSA project found new direction after 'anomalous' weather year forced ship's retreat

 

Extreme sea ice conditions and one of the world’s most powerful earthquakes bookended a two-month science expedition to the Antarctic Peninsula earlier this year, ensuring few dull moments for chief scientist Eugene Domack.

“It was very challenging,” said Domack during a recent phone interview. A geosciences professor at Hamilton College in New York, Domack was the lead principal investigator for the LARsen Ice Shelf System, Antarctica (LARISSA) project. “It required flexibility on an almost hourly basis.”

The LARISSA project — an interdisciplinary program to study different facets of the Larsen Embayment where an ice shelf had shattered apart less than a decade ago — assembled together dozens of scientists aboard the RVIB Nathaniel B. Palmer in January and February.

The researchers brought helicopters, huge sediment coring tools, automated deep-field stations outfitted with high-tech GPS instruments, and even a remotely operated vehicle (ROV) in what promised to be one of the biggest science campaigns to close out the International Polar Year (IPY).

And then the Palmer, a 300-foot-long icebreaker, ran into an unusually thick, impenetrable swath of sea ice in the Weddell Sea on the eastern side of the Antarctic Peninsula en route to the Larsen Embayment. The normal atmospheric and weather patterns that should have shoved all that ice clear never happened.

“It was almost like a year without summer,” Domack said.

Changing course

The team changed plans and course, steaming to the western side of the Antarctic Peninsula where it could get close to the coast and launch the helicopters across the spine of the peninsula to the east side when weather permitted. A fuel cache left at the seasonal Argentine research station, Teniente Matienzo Base, on the east side meant more fuel and an extended range for the helicopters.

“That allowed us to stretch their distance from that side of the peninsula,” Domack said. “Surprisingly, we managed to get a fair proportion of work done … through just coming up with some logistical thinking and out-of-the-box kind of response to the setting we were given.”

The ship-based scientists decided to throw much of their energy into supporting concurrent work by an ice-coring team on the Bruce Plateau, an ice field 2,000 meters high straddling a narrow ridge on the peninsula. That group, led by Ellen Mosley-Thompson, professor of geography at Ohio State University, recovered a 445.6-meter-long core, the longest yet drilled from that region of Antarctica.

The ice core team had its own challenges. Bad weather delayed its transport to the remote drill site, and snowstorms were a recurrent problem, preventing support flights to the team from the British Antarctic Survey’s Rothera Station. Their drills twice became stuck deep in the ice, a drill motor broke and all three of the drill gearboxes failed, causing them to cannibalize those devices to construct a new one.

“It was the field season from hell,” said Mosley-Thompson, in a press release from Ohio State University, where she is also the director of the Byrd Polar Research Center. “Everything that could go wrong did, and almost everything that could break did.”

Despite the setbacks, the team drilled down to bedrock ahead of schedule.

Complementary work

“The best outcome of the whole season was the ice core at Site Beta,” Domack said, referring to the camp on the Bruce Plateau. The Palmer parked in an area called Barilari Bay, just 12 nautical miles from the camp, where it drilled several sediment cores, which scientists can study for a number of purposes, from looking at the biology of the tiny critters living in the seafloor to reconstructing past climate conditions.

“We felt that getting some long cores of marine sediment from there off the ship would complement the climate record from the ice core in a way that we hadn’t planned on,” Domack said.

One of the main goals of the project is to build a climate history of the region to determine if the breakup of the Larsen B Ice Shelf in 2002 was part of a long-term natural cycle or an aberration brought on by climate change.

Previously, Domack and colleagues determined that the Larsen B had been in place for at least 10,000 years, during most of the present-day Holocene. The current epoch represents a naturally warmer interglacial period between ice ages, exacerbated in recent decades by human influences on the environment. The Last Glacial Maximum occurred about 20,000 years ago, when ice sheets even draped across parts of the present-day United States.

Sediment cores from the seafloor around the continental margin of Antarctica are nothing new. However, gleaning a climate record from analysis of the cores can be tricky and ambiguous. Domack said the cores from Barilari Bay would complement the Site Beta ice core and provide key insights into the best ways to interpret sediment cores for paleoclimate work.

“It’s going to be the Rosetta stone of going from ice cores to marine sediments,” he said.

On the go

Another team of glaciologists, headed by Ted Scambos, lead scientist at the University of Colorado’s National Snow and Ice Data Center (NSIDC), benefited from the quick work by Mosley-Thompson’s group.

A ski-equipped Twin Otter used to support the ice-core team was now available to fly Scambos’ crew from Rothera to the eastern side of the peninsula to install several AMIGO stations, for Automated Meteorology Ice Geophysics Observation systems.

These heavy-duty polar probes have built-in GPS units and weather station instrumentation. The AMIGOs, which also sport high-resolution cameras, should give the scientists additional insight into how the glaciers in the area behave, as well as how the remaining sliver of the Larsen B Ice Shelf evolves.

The team was able to set up three AMIGO systems and two separate GPS stations, despite spates of bad weather that grounded aircraft and stranded the scientists in temporary field camps for days at a time. Eventually, the glaciologists reunited with their colleagues on the ship via a rather circuitous route that took them from Scar Inlet on the east side of the peninsula back to Rothera.

From the British base, the scientists flew to Palmer Station, a U.S. Antarctic Program base on Anvers Island. The trick was that Palmer Station has no airfield, only a pier, so the Twin Otter had to land on a soft glacier behind the base.

On the team’s blog, Scambos noted that the runway was less than ideal: “It was the most rutted, cracked-up, slush-pit of a glacier I’d ever seen. It was sloped, with the end of it as steep as a ski run, leading straight to a boulder field.”

But the plane landed safely at Palmer Station, where the ARSV Laurence M. Gould, another USAP research vessel, was standing by to transfer the glaciologists to the Palmer for the northbound trip to Punta Arenas, Chile.

A veteran of nearly a dozen polar expeditions, Scambos said later via e-mail that the LARISSA project wasn’t his roughest physical challenge in Antarctica, but logistically it was the toughest.

“We needed to use all our resources, needed to be prepared to do any part of the work at any time, and we needed to be able to react to a completely different approach with short notice,” he said after returning home to Boulder, Colo. “But, I have to say, NSF was flexible and imaginative right along with us, and we were able to get a lot done. Otherwise, the ice conditions and the weather limitations — lots of low clouds — would have almost completely shut us down.”

Discoveries

There were also some scientific surprises along the way — though at least one discovery has potentially troubling implications for the fragile Antarctic ecosystem.

A remotely operated vehicle (ROV) brought by a Belgian team for the LARISSA project discovered a large number of invasive crabs moving up from deep water in a 1,500-meter-deep basin off Anvers Island referred to as the Palmer Deep.

Domack said that there must have been at least 100,000 crabs, which appear to have stripped the seafloor clean as they climbed to shallower waters made more inviting by climate change. “They’re decimating the Antarctic fauna. They’re an invasive species from Patagonia,” he said.

Craig Smith, University of Hawaii professor of oceanography on the LARISSA cruise, told the Honolulu Star-Bulletin in a recent interview that king crabs had been absent from cold Antarctic ecosystems for possibly millions of years, but with climate warming they are living far shallower than ever recorded.

“Climate warming in Antarctica is faster than anywhere on the globe,” he told the paper, and abundance of animals might decline as a result of warming, and “unique communities may change. Species may be lost.”

The ROV also spied less troublesome critters, like giant marine worms, an octopus, starfish and krill. The ROV, controlled by a three-person team from the Renard Center of Marine Geology at Ghent University in Belgium, carried a video camera to capture real-time images, as well as instruments to collect sediment, gas and water samples.

“The ROV was great,” Domack said. “We used it in as many situations as we could to resolve interesting problems that presented themselves as we worked through the cruise.”

Maria Vernet, a research biologist from Scripps Institution of Oceanography at UC San Diego, said the marine life on the seafloor was “extremely rich” on the western side of the peninsula. She said one hypothesis was that the plentiful phytoplankton in the upper surface of the waters fed the benthic communities below.

“Of course, we only had a snapshot in time,” she said.

Rocky road, good science

One problem the LARISSA team couldn’t solve was the thick pack ice in the Weddell Sea. The Palmer made a second effort to push into the Larsen B Embayment in February but again failed to penetrate to the former location of the ice shelf.

Domack said a later review of ice images since 1998, after the Larsen A Ice Shelf broke apart, showed enough open water every year that would have allowed the ship to reach most of its field targets. Only 2010 proved the exception to the rule.

“This was truly anomalous sea ice and weather year,” he said.

It was in that region five years ago that Domack and colleagues on a previous expedition found extraordinary signs of life on the floor of the continental shelf — bacteria so thick it was visible to the naked eye in what biologists call bacterial mats. The scientists had unexpectedly discovered a cold seep biological community, subsisting not on light, as most ecosystems, but on methane vented through the seafloor.

It was there that the researchers had hoped to return with the ROV and other instruments to study the cold seep community and drill into the sediments to learn more about the ice shelf collapse.

Domack said a follow-up LARISSA cruise is scheduled for 2012. Some of the unfinished work will be completed, he added, but other studies, such as of the bizarre bacterial mats, may not happen without an ROV.

A team of German researchers, who visited the region in 2007, is set to return to the Larsen Embayment next year, Domack noted. “We may just be beaten out of that even though we made the discovery. That’s the way it goes,” he said philosophically.

The ship and its crew had one last surprise as they steamed north back to Punta Arenas in Patagonian Chile. One of the world’s most powerful earthquakes had struck the morning of Feb. 27, creating widespread damage in the north of the country, including the gateway airport in Santiago.

The Palmer docked at Punta Arenas on March 1. The transportation disruptions stranded the crew and scientists for several more days. Domack lingered for a couple of more weeks to help with the scientific response to the earthquake after an exhausting two months at seas.

Despite what he called a “very difficult cruise,” Domack said he was pleased with the overall results, as well as the work ethic of personnel from Raytheon Polar Services Co. and Edison Chouest Offshore, the companies contracted to support the marine science program.

“It could have degenerated into a logistical waste of resources, but we were able to put it together, and I think we got some really good science out of it,” he said.

NSF-funded research in this story: Eugene Domack, Hamilton College, Award No. 0732467; Arnold Gordon and Bruce Huber, Columbia University, Award No. 0732651; Ted Scambos, University of Colorado at Boulder, Award No. 0732921; Ellen Mosley-Thompson and Lonnie Thompson, Ohio State University, Award No. 0732655; Maria Vernet, University of California-San Diego Scripps Institution of Oceanography, Award No. 0732983. Craig Smith, University of Hawaii, Award No. 0732711.

Share on Facebook Share on Twitter Share on Google Plus Share This Site on Pinterest Subscribe to USAP RSS Feeds Share Via Email
Curator: Peter Rejcek, Antarctic Support Contract | NSF Official: Winifred Reuning, Division of Polar Programs