Arctic waters teem with life beneath barren icescape
ABOARD THE USS HAWKBILL — Con, this is sonar. We've got whales."
Banter in the control room of the nuclear submarine USS Hawkbill quiets as the sonar operator pipes the distinctive cry of Beluga whales into the room. Meanwhile, as the sub glides effortlessly beneath the sea ice, images of jellyfish drift across a small TV screen linked to an upward-looking camera atop the sub's stubby superstructure.
From the Arctic ice cap, frozen desolation extends as far as the eye can see. The waters beneath, however, teem with life. Until now, trying to take a meaningful census or track changes in populations across the Arctic Basin has been difficult, if not impossible.
During the past five years, however, a research effort with echoes of Jules Verne's "20,000 Leagues Under the Sea," has given scientists an unprecedented look at life in this last oceanic frontier. For a few weeks during each of the past five years, US Navy submarines modified for civilian science have criss-crossed the ice-mantled Arctic Basin. The cruises have gathered a wealth of data on the sources, movement, and nutrient levels of water in the Arctic Ocean - a body several researchers suspect already is showing evidence of climate change.
Yet so little is known about the region and its aquatic inhabitants that scientists cannot say whether the changes they are recording are natural variations or early manifestations of global warming foretold by climate-change simulations.
Getting a better handle on the Arctic Ocean's ecosystems is one goal. In particular, researchers want to study the tiny plankton and diatoms that serve as the foundation for the region's food chain - from whales, Arctic cod, and seals to polar bears and people. They also hope to better understand how much carbon dioxide these tiny organisms lock up out of reach of the atmosphere.
"The Arctic Ocean is much more biologically active than people thought" based on studies conducted in the 1950s and '60s, says University of Alaska oceanographer Terry Whitledge during a break from his labors in the sub's torpedo-room laboratory. "There's more plankton, the populations are growing faster than we thought, and the diversity of life is broader."
Climate change and plankton
Four years ago, Dr. Whitledge explains, research conducted aboard an ice breaker uncovered populations of plant-like phytoplankton in the ocean's Canadian Basin two to five times higher than previously believed. "Those may seem like small increases, but they represent a quantity of carbon big enough to mean something" in the global carbon budget, he says.
Is this increase "the result of changing climate? Or did we mismeasure these populations 30 years ago?" he asks.
The suspicion, he continues, is that the increase may represent a change in phytoplankton distribution resulting from the intrusion of warmer, less nutrient-laden water from the Atlantic, documented on successive SCICEX cruises. This intrusion, reaching ever farther into the Arctic Ocean, is one of the early signals of global warming emerging from climate models.
During the cruise, Whitledge and colleagues Dean Stockwell and Steve Okkonen will have taken 23,500 water samples to try to answer these questions.
Every two hours, one member of Whitledge's team opens a valve that taps one of the sub's systems for filling ballast tanks with seawater. A small portion of each sample is run through filters and instruments on board. The majority is divvied up into small bottles for distribution to land-bound colleagues.
At 24 points along our sawtooth track - 740 nautical miles of "playing chicken" with northern Alaska's continental shelf - the sub will spiral downward to collect water samples. Taken at eight depths, the samples provide a look at how conditions change at each point.
Whitledge and his colleagues across the country will test the samples for diatoms and plankton, temperature, salinity, nutrients, and chemicals that trace the sources of the water to the Atlantic, Pacific, or the rivers that empty into the basin.
Understanding the flow of nutrients, as well as the circulation of water and ice, is crucial to monitoring a growing problem in the Arctic: the flow of pollutants from lower latitudes, as well as those generated in the region.
Polar bears and PCBs
Stephanie Pfirman, who heads the environmental science department at Barnard College, Columbia University says that while much of the Arctic remains pristine, contaminants such as PCBs are beginning to show up in polar bears at levels thought to bring about biological damage. Other contaminants, such as the pesticide HCH and Cesium 137, a radioactive isotope, are appearing in isolated locations and have no obvious source.
River runoff from the more-industrialized Eurasian Arctic is one likely suspect for some contaminants, Dr. Pfirman says. Other sources are more diffuse. HCH, for example, is used in Southeast Asia and readily vaporizes in the summer. Convection carries the vapor aloft, where it gradually drifts northward as part of the atmosphere's equator-to-pole circulation.
She and other researchers are concerned that while pollution levels in the region are low now, the physical structure of the Arctic Basin, the sources and movements of its water, and its top-of-the-world location leave it vulnerable to increasing levels of toxic compounds. As contaminants accumulate in the region, colder temperatures and weaker sunlight prevent them from breaking down as quickly as they would at lower latitudes. And a long food chain allows compounds to concentrate in organisms at or near the top.
With many of the Arctic's biggest riddles unsolved, the US science community is looking for ways to prop up the window SCICEX has opened.
More broadly, the NSF is increasing the amount of money available to pay for Arctic science, especially for the logistics of working in the region.
*Parts 1 and 2 of the series ran May 13 and 20.