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News - May 2002

NSF PR 02-36

Media contact:

 Peter West

 (703) 292-8070

Dispatch 2, from the Second Data-gathering Cruise of SO GLOBEC

a view out of the Baltic Room doors
A view out of the Baltic Room doors.
Credit: Ana Sirovic

Andres Sepulveda and Alice Doyle haul a CTD aboard
Andres Sepulveda and Alice Doyle haul a CTD aboard.
Credit: Kristin Cobb

April 15, 2002 / Off the coast of Adelaide Island, Antarctica: Science has begun in earnest aboard the R.V. Nathaniel B. Palmer. But just a few days ago, the Palmer's seven laboratories were empty.

As winds reached up to 60 nautical miles per hour (69 mph) through the Drake Passage -- a notoriously unpredictable and often violent body of water -- scientists experienced firsthand how life in the ocean depends on the movements of the sea.

"I'm glad I wasn't throwing up, that's for sure," said researcher Kristy Aller of the Scripps Institution of Oceanography in La Jolla, Calif. "But I didn't feel so hot. I guess none of us did really."

Ship's mate John Higdon, who has been crossing the Drake for three years aboard the Palmer, rated the passage 7 out of 10 for roughness. He estimated the waves climbed to 6 or 7 meters (20-25 feet) for a time. Though the 93-meter (308-foot) Palmer rides lesser swells with ease, this height was enough to tip chairs and knock keyboards to the floor in the ship's computer lab.

Cycling between weightlessness and descent, the sensation was much like being on an endless roller coaster. Once nausea hit, time seemed to pass very slowly. The mess hall was deserted but for the ship's hardy crew.

"I never really worry about getting seasick, only about getting sick of the seas," Higdon said. "If I had gotten seasick, I would have become a doctor," he quipped.

Then, just as quickly as the seas had stirred, the lurching motion subsided. The treachery of the Drake was forgotten as research took on a frenzied, 24-hour-a-day pace. The Palmer began its mission to map the structure and biology of the Southern Ocean along a 92-point, ladder-shaped grid off the Western Antarctic Peninsula.

Water in the ocean, far from being uniform, is organized into separate units, or masses, that have distinct features and histories. Differences in density and salt content prevent these water masses from readily mixing and maintain environments that may be as disparate as a rainforest and a desert.

"You'd be amazed how much structure there is," said Julian Ashford of Old Dominion University who is working with the Palmer's Conductivity, Temperature, Depth (CTD) group, charting the basic physical features of the sea. The CTD group will create maps that show high and low zones of salt, oxygen, and temperature; much like elevation maps show mountains and valleys.

Biologists aboard the Palmer will relate their observations of marine life to the findings of the CTD group. "What makes this cruise special is that we have a whole bunch of biologists focusing their work around the physical structure of the ocean," Ashford said.

Just like the topography of land governs its ability to support life, so too does the layout of the ocean.

For example, the Antarctic Circumpolar Current (ACC), which circles the continent, governs much of the life in the Antarctic. The current forms a swift-moving corridor in which animals can travel for thousands of miles. "They don't even know they are moving because their environment never changes," Ashford said. The current may also bring warmer, nutrient-rich oceanic water to the continental shelf of Antarctica, potentially affecting the biology there.

"Water movements affect where the food chain starts, where the green stuff is, where the krill is that eats the green stuff, and so on," said Andres Sepulveda, a graduate student from Old Dominion University who is also working with the CTD group.

Working in the "Baltic Room"

The CTD group will measure the physical properties of the water column and collect water samples at each of the 92 points, or stations, on the grid. Other instruments will measure currents, weather, and ocean depth as the ship travels the 8 kilometers to 40 kilometers (five to 25 miles) from station to station.

The CTD consists of a six-foot-high, three-foot-wide cylindrical frame holding instruments and submarine-shaped collection bottles arranged in a circle. At each station, CTD scientists and marine technicians lower the CTD into the sea via a cable and sheave that extends and retracts on an extensible arm from the ship's "Baltic room." The CTD takes measurements eight times a second and relays these to a computer in real time, via electrical wires in the cable.

When the Baltic room's two-story high door opens to deploy the CTD, it is like opening a door to another world. Deep blue water stirs against a paler, but still intense, blue sky. White-with-black Cape Petrel birds glide just above the water's surface, appearing illuminated beside the blue. Fresh, cold air, often mixed with snow flurries, drifts through the door.

Between the first few stations, marine technicians Alice Doyle and Jennifer White climbed the CTD's frame, as if it were a jungle gym, wielding their screwdrivers to tackle leaking bottles and other kinks in the system.

At the third station, engineer Chris MacKay added a "microstructure profiler," resembling a rocket, to the CTD. This device measures salt and temperature like the CTD, but takes 512 samples per second instead of eight, thus tracking finer variations in water structure.

To illustrate the device's function, consider what it could reveal about a simple cup of coffee. MacKay recounted this analogy from a colleague: "He said that if you took the coffee, poured in some cream, stirred it and then profiled through it, you could tell the original temperatures of the coffee and the cream, how much energy was put into the system when you stirred it, how long it would take to totally mix, and when it would stop moving."

Each time the CTD is reeled back into the Baltic room, scientists with test tubes and bottles swarm the machine like vultures, ready to grab their water samples.

First in line are chemists like graduate student Rob Masserini of the University of South Florida, who will examine the nutrient contents of the water layers. "These nutrients are essentially fertilizer that phytoplankton use to grow. They support the base of the food chain," he said.

Masserini is particularly interested in ammonia, a form of nitrogen that phytoplankton readily take up to make proteins. Last year's SO GLOBEC cruises revealed startlingly high levels of ammonia and unexplained seasonal shifts in concentrations along the Western Antarctic Peninsula.

As to why that is the case, Masserini said, "we have no answers only questions."

The first days of data collection were a jumble of equipment tweaks and test runs, not only for the CTD group, but also for scientists studying plants and animals from algae to whales. Lead CTD scientist John Klinck of Old Dominion University said things would calm down soon, however.

"In a few days, this will be as coordinated as a fine ballet," he said.




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