Travel to one of the coldest, windiest, and most barren places on Earth does not require a passport. This isn’t because of Antarctica’s inhospitable conditions or lack of long-term residents. It’s because of an agreement of no territorial claim among 53 countries that have vested research interests in this massive snow-covered landmass at the South Pole that is roughly the size of the U.S. and Mexico combined, said Alexa Sterling, a Ph.D. candidate at the University of Rhode, at a recent lecture.
Sterling was one of two presenters at the Bay Informed discussion series at the Graduate School of Oceanography (GSO) in November to discuss recent research expeditions looking at the impacts of climate change on diatom populations in the Southern Ocean that surround Antarctica and ice production in the Ross Sea, a deep bay of the Southern Ocean.
While the untouched wilderness, towering ice shelves, and abundant wildlife draw more than 40,000 tourists each year, more than 800 scientists and their support teams from around the world conduct research in Antarctica annually because of its vital role in the Earth’s climate and ocean systems.
Antarctica holds about 90 percent of the Earth’s ice, which locks up about 70 percent of the world’s freshwater. In addition, the Southern Ocean absorbs a significant amount of carbon dioxide from the atmosphere and connects to all the other three major ocean basins (Atlantic, Pacific, and Indian) – driving global circulation of cold, salty waters that supply oxygen to deep layers of the ocean and of warmer surface waters flowing south that affect climate through the transport of heat (Global importance of Antarctica).
Sterling and co-presenter Sam Gartzman, a masters student in chemical oceanography at GSO, participated on different cruises at different times of the year aboard the Nathaniel B. Palmer. Sterling’s six-week research expedition during Antarctica’s summer months focused on the biology of diatoms to help scientists better understand food web functioning and carbon uptake.
“They’re small, photosynthetic phytoplankton that are the base of the food web similar to plants on land. They produce oxygen and are carbon sinks,” said Sterling.
Though you wouldn’t be able to see diatoms without a microscope, their shells are loaded with carbon. When they die, they sink to the seafloor, carrying carbon from the surface waters to the sediments below. This process is especially efficient in Antarctica where deep water is formed.
“You have really cold and salty water, which makes very dense water that sinks,” said Gartzman, describing areas of sea ice production in the Ross Sea referred to as polynyas.
Gartzman was a part of the 65-day PIPERS (Polynyas, Ice Production & seasonal Evolution in the Ross Sea) cruise that hosted 27 scientists from eight countries and 14 institutions from April to June (read cruise blog). The goal of the trip was to study Antarctica’s winter ice production and water mass formation at these sites.
These polynya regions, he said, are the result of strong, katabatic winds coming off the ice sheets and sloping downward off the coast, blowing open holes in the sea ice.
“Polynya is a Russian word that literally means ‘ice hole’,” said Gartzman, noting that when the wind blows open these holes, it pushes the sea ice out and creates space for new sea ice to form. When more sea ice is formed, he explained, brine rejection – a process where salt accumulates in the surrounding water as it is expelled from ice as crystals form – occurs. The result is water that is saltier and denser.
The Ross Sea is a major ice factory for the region with the Ross Sea polynya measuring between 100-300 nautical miles and the neighboring Tera Nova Bay polynya measuring 100 nautical miles across, added Gartzman.
“The reason that [polynyas] are really important is that this sinking water leaves Antarctica, travels northward through the Pacific, and stays at the bottom of the ocean for hundreds of years. It is the largest water mass in the ocean, this Antarctic bottom water, and it’s formed in these polynyas.”
The problem, he said, is that this bottom or deep water formation has been slowing over the last couple of years. This is occurring despite the fact that ice formation has increased in Antarctica over the last 10 years while it has drastically decreased globally.
“It highlights why we need to collect samples at this time when polynyas are occurring,” he said, explaining this will help scientists better understand the conditions for ice formation and bottom water production, and their implications for other ocean and climate processes.
The Bay Informed Discussion Series is supported by Rhode Island Sea Grant in partnership with GSO. This series is held the third Thursday of the month at 7 p.m. at the GSO Bay Campus in Narragansett. There will be no discussion in December. These events are designed for the community to learn more about research at GSO.
The next event will be on January 18.
– Meredith Haas | Rhode Island Sea Grant Research Communications Specialist