Bottom of World Tops for Climate Change Studies

Nausea-inducing ocean swells, numbing cold, and 18- to 20-hour workdays aren’t ideal conditions for conducting research, but then again, Antarctica isn’t your normal, everyday laboratory. For Drs. David DeMaster and Carrie Thomas, the opportunity to head to the bottom of the world to study climate change is worth the physical hardship and grueling schedule. The two Department of Marine, Earth and Atmospheric Sciences professors traveled to Antarctica in February and plan to make two more trips in the coming year to measure how global warming is affecting sea life and ice formation.

Less polar sea-ice could mean a greater build-up of greenhouse gases in the atmosphere over time because of reductions in “bottom water” formation.

DeMaster and Thomas spent more than a year preparing for their three expeditions, compiling a 50-page list of scientific equipment, cold-weather gear, and other materials needed for the trip. Together with a research team from the University of Hawaii, the two professors and five NC State graduate students are taking an ice-breaker research vessel operated by the National Science Foundation (NSF) on the three-week treks to five research sites along the Antarctic Peninsula, which juts northward from the frozen continent towards the tip of South America. “It’s more like being in the Marines than on any cruise ship,” says DeMaster, who has been on 10 previous trips to Antarctica since the 1970s.

On the four-day journey from the southern tip of Chile to Antarctica, the round-hulled ice-breaker must navigate some of the choppiest seas on Earth. “In that part of the world, there’s nothing to stop the wind and waves,” DeMaster says. “It’s four days of rockin’ and rollin’. Much of the time, you just hang tight in your bunks.” Upon reaching the Antarctic Peninsula, they begin non-stop work. The continent serves as an international scientific laboratory, with a few dozen U.S. research teams visiting every year. The trips are expensive—the NSF ship costs $30,000 to $40,000 a day to operate—so data needs to be collected efficiently. The scientists work 12-hour shifts gathering samples for the entire ship, and they spend much of their off time tabulating their own results. “You don’t have any trouble falling asleep after that long a day,” DeMaster says, “and the cold weather wakes you up and keeps you awake when you’re on watch.”

DeMaster and Thomas conducted a series of Antarctic expeditions almost a decade ago to examine how marine creatures like sea cucumbers, urchins, and large worms survive the polar winter. The lack of light at the surface during those months limits the amount of fresh plankton, which in turn affects how much food falls to the always-dark depths 600 meters below. “We’re trying to see how animals adapt to changing food patterns,” Thomas says. Now, they are building on those studies, comparing current findings with previous ones to assess the effects of climate change. The NC State team cores the seabed for sediment samples, deploys roving remote cameras to take underwater pictures, and uses net trawls to capture the sea creatures for examination. Thomas measures metabolic activity in the microbial community, while DeMaster checks feeding patterns by examining levels of thorium-234, which occurs naturally in plankton and serves as a radioactive tracer.

“Antarctica is warming as fast as anywhere in the world.”

The five research stations visited by the team are located between 64º and 68º latitude south—the equivalent of central Alaska in the north—with the southernmost areas experiencing more ice coverage until lately. Scientists have found dramatic drops in the amount of polar ice in recent years, and DeMaster says less sea-ice formation could mean a greater build-up of greenhouse gases in the atmosphere over time. As sea-ice is formed, the dense, salty water left behind sinks to the ocean floor and becomes the “bottom water” that circulates in the deep around the globe. Carbon dioxide from the atmosphere readily dissolves in the sinking, frigid water, allowing the ocean to annually take up about a third of the CO2 released globally into the atmosphere by human activity, he says. Fluctuations in sea-ice formation also impact the food chain, altering the amount and type of plankton and algae available for larger marine creatures. The NC State team is examining how the creatures are responding to the changes and measuring rates of microbial activity and carbon recycling in the sediment to glimpse the future impact of global warming. “Antarctica is warming as fast as anywhere in the world,” DeMaster says. “It’s our canary in the coal mine, so it’s a pivotal place to understand global warming.”


Drs. David DeMaster and Carrie Thomas All photos courtesy of FoodBANCS2 Project

Graduate students Brian Pointer and Kim Null sample a Kasten corerís probe of ocean floor sediments.

A strong sign of global warming, invasive species of grass, moss, and insects are found by penguins in an area previously covered by ice and snow.

Researchers deploy a sediment trap for a year-long collection of particles and phytoplankton blooms settling on the ocean floor.

David DeMaster and NC State graduate students Rebecca Pirtle-Levy, Linda Waters, Alyssa Hopkins, and Brian Pointer join University of Hawaii students on a sampling excursion.

Echinoderms, or Brittle Stars, photographed by remote camera on the Southern Ocean floor.