Ice in excess

Sea ice is a fickle thing. Sometimes there's too little. This year there's too much off the Antarctic Peninsula and in McMurdo Sound.

Icebergs large enough to be small states are partially blocking the flow of water to McMurdo Sound, holding the sea ice solid.

One of the bergs, B-15, extends about 1,000 feet down, blocking the currents of water that usually circulate through McMurdo Sound and help move the sea ice out.

"It's turned this whole area into a mill pond," said Ted Dettmar, lead instructor at Field Safety Training Program.

Many years winter storms blow out the sea ice, leaving open water in July, Dettmar said. By the time the Coast Guard ice breakers arrive in December the ice edge is typically 15 to 20 miles (24 to 32 kilometers) away from McMurdo Station.

This year people wintering at McMurdo Station never saw open water, Dettmar said. The sea ice is now 9 feet (3 meters) thick in front of McMurdo, and 10 to 14 feet (3 to 4.4 meters) thick at the runway. The sea ice extends past Cape Bird and Dettmar expects the ice breaker may have to cut through more than 70 miles (113 kilometers) of ice to reach McMurdo.

The Coast Guard has also been keeping tabs on the ice edge situation. The Polar Star is coming out of dry dock and is scheduled to start breaking a channel to McMurdo on Dec. 28. The ice could change dramatically by then, said U.S. Coast Guard Lt. April Brown. Or not.

"Of course we are researching contingency plans for both (ice breakers) on a 'what if' basis, just to keep something in the back pocket," Brown said. "That's just prudent planning."

The expanse of sea ice to the north is protecting sea ice nearer, Dettmar said. Sea ice around the Barne Glacier and other areas usually riddled with cracks is remarkably stable.

"Areas where we typically see pressure ridges and fairly major cracks, this year what we're seeing is flat," Dettmar said. "It's made the ice in some ways easier to travel, but for the science groups they don't have anything to study."

Penguins and seals use cracks as doorways, to gain access to traditional rookeries and colonies for rearing young and breeding. With fewer cracks and a more distant ice edge, they must work harder and travel farther to reach these areas. As a result, many are expected to not reach the coastal areas of McMurdo Sound this season. A science group studying Weddel seals has found less than 150 adults in the study area, which extends from Scott Base to Cape Evans. This is less than a third of the number seen by this time last year, said seal scientist Michael Cameron.

"We've known that there's a relationship between ice extent and the number of animals in the study area," Cameron said. He's spent more time in helicopters than usual, searching for seals nearer the ice edge.

"To my knowledge this is the greatest summer sea ice extent that's ever been recorded in McMurdo Sound," Cameron said. "Everybody's guess is that it's due to this giant iceberg off of Cape Bird blocking the swells that would normally break up any sea ice in the area."

At the same time, scientists studying the sea ice actually have an overabundance. Last year the sea ice near McMurdo was 40 percent thicker than usual, and this year it's thicker still, said scientist Dave Cole, from the Cold Regions Research and Engineering Labs. Cole works with a group of scientists studying the structure of ice and how it cracks.

"Our overall goal is to develop a better set of models for the way ice breaks up," Cole said.

To study that, they cut out free-floating blocks of sea ice and record how they react to certain stresses. But if the ice is more than a meter deep it is difficult to cut and work with. Though they'd prefer to be closer to McMurdo, they had to move their camp a few kilometers north, near Cape Barne.

Sea ice researchers off the Antarctic Peninsula also found more ice than they really hoped. Ice piled up to the railing of the Nathaniel B. Palmer, extending the research vessel's cruise in Marguerite Bay.

For more than three weeks the research vessel maneuvered in about 197 feet (60 meters) of open water in Marguerite Bay south of Palmer Station, surrounded by slabs of ice that extend as much as 60 feet below the surface. Northerly winds packed the sea ice in around the Palmer, an ice-strengthened ship. The Palmer can break through more than 3 feet (1 meter) of ice continuously at a speed of 3 knots (3 1/2 mph/5 1/2 kph), and up to five meters of ice backing and ramming. But the ice surrounding it was too thick, so the crew and passengers had to wait for the wind to shift and blow the ice away again.

"They're fine, they're safe, they're doing science," said Al Hickey, marine superintendent for Raytheon Polar Services Company. "They're just going to play a waiting game. The ship's in no jeopardy, the people are in no jeopardy."

The cruise was part of a long term ecological research project, studying the biology and dynamics of the frozen Southern Ocean. This time the researchers particularly wanted to look at the dynamics of ice.

"They are where they want to be. They got what they want," Hickey said. "It could probably be termed a very successful cruise."

The Palmer was scheduled to leave Marguerite Bay on Oct. 14, but the six-day delay was not an issue, Hickey said. The ship was stocked with plenty of food, water and fuel. After the ice opened up again Oct. 20, the Palmer headed north. It arrived in Punta Arenas Friday morning.

The Palmer has broken smaller research vessels out of the ice before, but this was the first time a U.S. Antarctic Program research vessel has been waylaid in the ice for an extended period of time, Hickey said.

During the delay, scientists and crew on board made the best of the unique situation, entertaining themselves with music and foosball tournaments.

"They're actually enjoying, apparently, some incredible scenery, which obviously they wouldn't get otherwise," Hickey said. "And more opportunity to conduct science for a longer period than they expected."