Ice station pieces together Arctic's global sway
APL ICE STATION, ARCTIC OCEAN
A cluster of plywood and fabric hootches huddle as if for warmth on an ice floe 130 miles north of Barrow, Alaska.
Inside one 8-by-20-foot box, Peter Mikhalevsky is using the undersea travel time of sound across the Arctic Basin to take the Arctic Ocean's temperature.
Before his two-week tour is up, Dr. Mikhalevsky will spend 41.4 minutes gathering data. Those 41.4 minutes, however, confirm that during the past five years, the ocean has warmed by nearly 1 degree F. This comes on the heels of ice-breaker and acoustic measurements in 1994 that found a similar increase over what would have been expected given historical records.
Meanwhile, deep under the ice, the US Navy's nuclear attack submarine USS Hawkbill is launching probes as it traverses the Arctic Ocean, measuring the temperature, density, and, indirectly, the saltiness of the water along the sound's path.
The temperatures it measures will test the acoustic system's accuracy - already in good agreement with '98 probe results. Density and salinity data will help interpret and confirm temperature calculations based on the sound's travel time from a source the Russians installed last year between Franz Joseph Land and the Svalbard Archipelago. The set-up is part of a three-year US-Russian program to track ocean temperatures at the top of the world.
The APL ice camp and the USS Hawkbill form the dual research platform for SCICEX 99, the last annual installment in a five-year pact among the US Navy, the National Science Foundation, and other federal offices interested in giving civilian scientists unparalleled access to the least understood marine and atmospheric system on the planet. The system is seen by many climatologists as an early indicator of, and perhaps catalyst for, long-term climate change.
The chief scientist for the project is Margo Edwards, director of the mapping research group at the University of Hawaii's Institute of Geophysics and Planetology at Manoa. Under Navy rules, Dr. Edwards couldn't remain aboard the sub for the entire voyage. The ice camp, unique to this year's cruise, serves as a port from which Edwards and visitors could embark for key parts of the Hawkbill's cruise. The camp, run by the University of Washington's Applied Physics Laboratory (APL), opened an opportunity to expand SCICEX 99's agenda to include experiments such as Mikhalevsky's.
As Mikhalevsky, a marine scientist with the San Diego-based research firm Science Applications International, surveys the initial results from his acoustic thermometer - an early preview of what to expect from a larger system the US and Russians have installed - he exclaims, "The data are really beautiful! But more challenging than getting precise measurements is answering: What do they mean?"
At first blush, SCICEX evidence points to potentially ominous trends. During the 1990s, the Arctic ice cap has lost 20 percent of its mass, although only 5 percent of its surface area. The glistening ice that supports our camp melts from underneath.
Arctic sea ice is an important player in climate for two reasons, says Andrew Weaver, a climate modeler at the University of Victoria at Victoria, British Columbia: "Ice is white, and ice is made of fresh water."
Because it already floats in the ocean system, a melting Arctic ice cap would have little direct effect on sea level. The seasonal loss of ever-larger portions of the cap, however, could strip the ocean of its reflective cover, allowing the water to absorb and retain solar heat. Warmer waters would, in turn, speed melting.
The buoyant fresh water would enter the North Atlantic, where it would ride atop the saltier Atlantic water, slowing and perhaps pushing southward currents that moderate northern Europe's climate. Given the North Atlantic's key role in driving ocean currents worldwide, changes in Atlantic circulation would affect current and climate patterns around the globe.
During the SCICEX program's trial cruise in 1993, James Morison of the APL's Polar Science Center gathered data that showed warm Atlantic water pushing ever farther into the Arctic Basin. A layer of water insulating the ice from the Atlantic layer had thinned compared with measurements taken in 1991. By '95, that insulating layer had disappeared, says Michael Steele, a senior oceanographer at APL who took the measurements on that year's SCICEX cruise.
Yet, he adds, initial studies of similar data from the 1998 SCICEX cruise suggest that the ice's insulating layer may be growing. "1998 is looking like 1993 again," Mr. Steele says.
The data hint at a notion dawning on researchers: The Arctic is a more dynamic region than anyone thought. Nowhere does that show up more clearly than in the climate record.
Last fall, University of Washington researchers David Thompson and John Wallace published an analysis of nearly 100 years of wintertime Arctic temperatures and sea-level air pressure. They uncovered what they say is a periodic swing in conditions they dubbed the Arctic Oscillation. These changes at the surface reflect more pronounced shifts in the stratosphere, at altitudes of roughly 12 miles, says Dr. Wallace.
When the oscillation peaks, surface air pressures at high latitudes fall, and storm tracks - the battlegrounds where warm air and cold air meet - shift farther north. When the oscillation ebbs, the surface pressure in the Arctic rises and storm tracks push farther south, leading to cold-air outbreaks in Siberia and North America.
These swings occur on time scales ranging from weeks to a decade and represent what Dr. Weaver calls a principal mode of climate variation in the atmosphere - and a driver of North Atlantic climate swings that once were thought to be governed by their own oscillation.
"Some of the people who study the Arctic like this notion because it's a way of unifying" changes in river runoff, ice drift and thickness, and ice-edge positions, Wallace says.
Superimposed on the oscillation's shorter-term swings, however, is another trend: The oscillation's wintertime peaks have strengthened during the past 30 years. Some climate models, including a simulation published last year by NASA atmospheric physicist Drew Shindell, suggest that global warming could strengthen the oscillation. Others trigger stronger peaks through ozone loss in the Arctic stratosphere.
If these peaks continue to strengthen, Mr. Thompson and Wallace hold that the next century could see changing rain and snowfall patterns in Eurasia, a shift in North Atlantic fishing grounds, even the disappearance of Arctic ice in the summer.
"Interestingly, theories predict that we should see a cooling of the Arctic starting about now," says Mikhalevsky, referring to swings in the Arctic Oscillation.
In the absence of future sub missions like SCICEX, Mikhalev-sky says, acoustic sensors like the one at the ice camp could provide the stream of data needed to test those theories.
* Part 1 ran May 13. On Tuesday, May 25, Peter Spotts will explore life on a submarine in The Home Forum's Kidspace.