Photo Credit: SIMBA

SIMBA scientists set up an ice mass balance buoy on an ice floe in the Bellingshausen Sea. The buoys boast a number of different instruments, from GPS to acoustic sensors, located above, within and below the ice to measure different properties as the floe moves and evolves.

Science team goes with the 'floe' after shipboard fire changes cruise schedule

The cruise

The SIMBA cruise had originally set course for the Amundsen Sea from Punta Arenas, Chile, but a shipboard fire in a laboratory room radically altered the schedule. While the fire was quickly contained with no injuries, the Palmer eventually returned to Chile for repairs and cleaning after only a few days at sea.

The expedition lost about 20 days, a third of its schedule. A new plan called for a study site closer to Punta Arenas — the Bellingshausen Sea.

“The original intent was not to go into the Bellingshausen Sea. It was more of a target of opportunity where we could get a significant amount of work [accomplished] in the period of time we had left,” Ackley said.

“The idea was to find a floe that was stable enough for a roughly 30-day period,” he added. An ice floe is a floating chunk of sea ice that is less than 10 kilometers in its greatest dimension. The floe the Palmer found, dubbed Ice Station Belgica after an historic expedition in the same area, was about 2.4 kilometers in diameter. Over four weeks, the scientists measured, cored, dug and sampled the floe’s ice, snow, slush and water.

“It turned out to be a very fortuitous choice, in the sense that we were able to investigate a lot of different ice types, find the sites that we needed for the time series work, and the floe we ended up with was fairly stable the entire time we were there, which is fairly remarkable in this type of business,” Ackley said.

In fact, despite the delays due to the fire and storms that hit the floe in October, Ackley said SIMBA accomplished most of its goals. The exception was the deployment of drift buoys that would continue to provide data on the sea ice lifecycle throughout the year. The scientists did manage to set out a couple of buoys that transmitted additional information through November.

“The buoys are working after a fashion,” said Ackley, a couple of weeks after the cruise ended on Oct. 31. “They are melting out a bit, and we are losing some sensors, but I think we’ve achieved that goal of getting an extension of the floe time series in the period since we left the ice.”

Importance of being algae

One of the many subprojects of the cruise involved studying the microorganisms that make their home on the ice. Chris Fritsen, with the Desert Research Institute in Nevada, is an ice biologist interested in the role of cold-loving algae in the Southern Ocean.

Part of his work involves unraveling how the algae develop in different types of ice at different times of the year, as well as understanding their place in the Southern Ocean food web.

“They grow in a myriad of different types of [ice] environments,” Fritsen said.

Adapted to cold, salty habitats that are flooded with 24-hour sunlight for part of the year, these microorganisms grow abundantly enough to give the sea ice a mottled and often dark, brownish-green color.

Like most organisms with a niche in the polar regions, these algae must be hardy in many ways to survive and thrive. “They have to be able to photo-adapt, grow in cold temperatures, and deal with hyper-saline conditions,” Fritsen said.

To avoid freezing to death, several sea ice microorganisms can produce proteins that alter how ice crystals grow, according to Fritsen. “These are proteins that actually glom on to the ice crystal and affect how it forms,” he said. “It’s thought that those can prevent ice formation in the cells themselves.”

And they have to pull through the long polar night. Some strains, Fritsen said, are able to switch from an autotrophic existence — relying on photosynthesis — to heterotrophic, absorbing some nutrients in the ice.

“That’s not a broad adaptation for all algal strains,” he noted.

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