Photo Credit: SIMBA

A crabeater seal and her pup lie on sea ice in the Bellingshausen Sea. The SIMBA expedition was one of the few to make direct observations of crabeater seal breeding behavior.

Belgian contingent interested in sea ice and gas fluxes

Natural carbon sink … and what stinks?

The algae also play a role in gas fluxes, a process of particular interest to the Belgian investigators on SIMBA. The algae are involved in localized carbon processes, but also play a critical role at a global level as a carbon dioxide “sink” to absorb excess CO₂ from the atmosphere, according to Jean-Louis Tison, a co-principal investigator from the Université Libre de Bruxelles in Belgium.

“A rough calculation based on our — alas, very few — first measurements of sea ice-atmosphere CO₂ fluxes suggest that sea ice is a CO₂ sink for probably more than 10 percent of the whole open water CO₂ sink south of 50 degrees south,” he said via e-mail, based on calculations by scientist Taro Takahashi at Lamont-Doherty Earth Observatory of Columbia University and others.

“If we consider the new estimates from the same authors that will soon be available, this [percentage] might double,” Tison added.

The phytoplankton also produce dimethyl sulfide (DMS), a gas you may not have heard of but have certainly smelled. It’s a component of that distinctive salty ocean odor, and it’s an important gas for cloud condensation nuclei, or cloud seeds, small particles about which cloud droplets coalesce. The number and type of cloud condensation nuclei can affect the properties of clouds, and may play an important role in moderating climate through their aerosols’ effect on backscattering solar radiation and in cloud formation.

DMS and its precursor dimethyl sulfoniopropionate (DMSP) can be found in concentrations in sea ice at three orders of magnitude as those found in surface ocean waters, according to Tison. How much of these gases are actually released into the atmosphere? And what role do their byproducts, such as dimethyl sulfoxide (DMSO), a sulfur-containing compound, play?

Those are still subjects of debate, Tison said, but DMS is a potentially important contributor to the atmospheric impact on climate variability.

“Our measurements of DMS and DMSP during SIMBA are unique since they document, for the first time, the evolution of those compounds within the sea ice cover, at high resolution … and in the course of a full month of contrasted meteorological conditions leading to flooding-freezing cycles,” he said. “Those cycles have had drastic impacts both on physical and biological processes within the sea ice cover.”

Higher up the food chain

The sea ice and algae also provide a critical habitat for animals at all levels of the food chain, beginning with krill, the main diet of larger Southern Ocean animals like penguins, seals and whales.

“[The algae’s] critically important role, we believe, is that they feed juvenile stages of krill and other zooplankton at critical times of the year,” Fritsen said.

The study of the cute and charismatic animals, from seabirds to seals, fell to SIMBA scientists like Brent Stewart. A co-principal investigator from Hubbs-Sea World Research Institute based in California, Stewart documented the composition and distribution of the marine mammals and seabirds.

“The opportunity to observe wildlife in the deep pack ice in late winter was rather unique, and particularly in the Bellingshausen-Amundsen seas area where only one other previous expedition had been: the Belgica Expedition from 1897-1899,” Stewart said via e-mail from San Francisco, where he was involved with cleanup efforts from an oil spill.

“This was an expedition of discovery for marine mammals and seabirds much as the early 19th century and early 20th century expeditions were, which made it all that more exciting,” he added.

For instance, Stewart said that there has been little recorded observation of crabeater seal breeding behavior, so the expedition was an exceptional opportunity for that type of work. At that time of the year, the crabeater seals are giving birth and nursing pups. “Most mating likely happens in mid-November, though we saw a few weaned pups, so a few females at least are mated in late October,” Stewart said.

Next on the agenda

The field season is over, but now comes the data crunching, when two months’ worth of fieldwork translates into two years of study. “There is much, much analysis that has to go on,” Ackley said.

And it’s not just data collected from the Palmer cruise that will keep researchers busy. Concurrent with the SIMBA cruise but on the other side of the continent, off the coast of East Antarctica, the Australian Research Science Vessel Aurora Australis conducted a similar sea ice survey. Another IPY expedition, the Sea Ice Physics and Ecosystem eXperiment (SIPEX) project involved about 45 scientists from eight countries.

“We’ll be interacting with them over the next few years to make some comparisons between the two areas,” Ackley said.

For Stewart and his colleagues, the expedition provided them with a wealth of new information.

“It was a tremendous opportunity to visit a rarely visited and wonderful part of the planet,” he said, “every minute there was different, with discoveries and observations that could hardly have been anticipated.   

“Science is about discovery and about keeping the enthusiasm for science and science education alive and vital, so this expedition was clearly, I think, a huge success from that perspective.”

NSF-funded research in this story: Steve Ackley, Department of Geological Sciences at the University of Texas San Antonio.

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