SHEBA Breaks Free of Arctic's Icy Embrace
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The Canadian Coast Guard icebreaker Des Groseilliers has left the ice floe it has called home for more than a year and is expected in Prudhoe Bay, Alaska, later this week, concluding the field season of the largest and most complex project ever supported in the Arctic by the National Science Foundation (NSF).
"We've observed the ice, the atmosphere and the ocean over a full annual cycle covering the physical variables in all three systems. We've seen it all: melting, freezing, heating, cooling, ridges, cracks, leads, melt ponds and all kinds of different formations of ice and snow," said Richard Moritz, polar scientist with the University of Washington's Applied Physics Laboratory and director of the SHEBA project office based at the university. The Des Groseilliers is expected to anchor off Prudhoe Bay Oct. 14 or 15 to offload personnel and cargo.
Purposely frozen into the ice pack early last October, the Des Groseilliers became the heart of Ice Station SHEBA, short for the Surface Heat Budget of the Arctic Ocean. It is a $19.5 million research effort to gather data to improve Arctic climate models and, in turn, global forecasts of climate change, said Mike Ledbetter, director for NSF's Arctic System Science Program.
The Arctic ice pack undergoes profound changes every year. In winter, the ice pack is about the size of the continental United States; in summer, there is only half as much ice. Understanding what controls this annual freeze and meltdown is a key to predicting future climate change and assessing the toll of global warming, whether it's natural or human-caused.
Warming could, for instance, affect westerly winds and change weather patterns in the northern hemisphere, Ledbetter says. It certainly would affect the web of life in the Arctic that ranges from microscopic algae on the sea ice to 1,600-pound polar bears that roam the surface.
A better understanding of the consequences of global warming in the Arctic would be important as world governments debate options that range from doing nothing to taking drastic steps to curtail the production of greenhouse gases.
SHEBA documented how such things as clouds, snow, ice and the ocean interact and exchange energy over the course of a year. "The data collected is unprecedented and will be used for decades to improve climate predictions," Ledbetter said.
The ice station, funded by NSF with support from the Office of Naval Research and the Japanese government, was located on a floe that originally was 5 miles by 6 miles. The station consisted of a collection of plywood research huts, cold-weather tents, meteorological towers, automatic buoys and stands of instruments surrounding the Des Groseilliers. The icebreaker was used under an agreement between the Office of Naval Research, NSF and Canadian Department of Fisheries and Oceans.
Small planes able to land on the ice and U.S. icebreakers provided the means to rotate scientists and crew during the experiment. The number of scientists working on site ranged from 15 in mid-winter to about 35 last spring.
Data also was gathered by sensors on six spacecraft, by researchers using four different kinds of aircraft and by a submarine prowling beneath the ice cap. The work was done in collaboration with U.S. agencies such as Department of Energy, NASA and the Navy. SHEBA was concerned with how the climate of the Arctic works, not with trying to determine if global warming is underway in the Arctic Ocean, Moritz said. Nevertheless, scientists were surprised in October 1997 that the water was much fresher than in measurements made in the same area 20 years ago. It was determined that the melting of the ice pack during the summer of 1997 caused the lower salinity. The findings were published in Geophysical Research Letters in May.
The ice where the station was established a year ago also was thinner than expected, Moritz says. Scientists had hoped to find ice of two to three meters in that area but despite searching some 50 miles farther north, settled on a floe that was between 1.6 and 1.8 meters thick. Going even farther north would have placed SHEBA beyond the limit of the Twin Otter aircraft used most of the year to reach the ice station from mainland Alaska.
Factors at work since last fall, including some effects from the El Niño event, produced a winter where the pack didn't thicken as much as seasoned ice experts had expected. Preliminary analyses of late summer measurements indicate that the floe lost more ice than it gained last winter.
Weather, ice and ocean conditions also combined in unexpected ways to move the floe farther and faster from its starting point than anyone predicted. Originally frozen in about 300 miles north of Prudhoe Bay, the floe was shoved along a meandering, 1,000-mile path ending up about 400 miles northwest of where it started.
Along with moving the ice floe, sometimes at a rate of 20 miles a day, the wind and ocean currents rearranged the station itself a number of times. During blizzard conditions in early April, for instance, the part of the camp with a 70-foot meteorological tower and seven huts migrated a quarter-mile away from the ship - overnight.
For more information, see: http://sheba.apl.washington.edu
Editors: B-roll is available on Betacam SP. New images of the ship's departure are expected by early November. Contact Dena Headlee at 1-888-937-5249 (pager).
FACT SHEET: SHEBA Quick Facts and Figures
Background: Ice Station SHEBA (Surface Heat Budget of the Arctic Ocean) is completing one year of being frozen in the Arctic ice gathering information to improve climate modeling.
- Ship (Des Groseilliers) froze into the Arctic ice pack Oct. 2, 1997 and pulled away Oct. 11, 1998.
- Ice Station SHEBA originally froze in at 75 degrees North and 143 degrees West, about 300 miles north of Deadhorse, Alaska. When the station concluded, it was at 80 degrees north and 166 degrees west, about 400 miles northwest of where it started.
- Des Groseilliers: 322 feet long; French-Canadian crew. After leaving Prudhoe Bay, expected to arrive in Quebec City Oct. 28.
- The last ship to sit deliberately in the ice pack for more than a year was the Fram, a Norwegian vessel that was frozen into the ice in 1893 for the purpose of scientific exploration. The Fram drifted for nearly three years before being able to break free.
- The smallest science party was 15 in the dead of winter and between 35 and 40 during spring's most intense periods. The Canadian Coast Guard crew consisted of 16 members, about half the number when the ship is underway.
- More than 170 scientists worked at the station at one time or another including principal investigators, technicians and graduate students. Most rotated at regular intervals, however, one American stayed six months straight and one Canadian biologist never left the station.
- More than 50 U.S. researchers received SHEBA funding from the National Science Foundation and Office of Naval Research to conduct projects. Other agencies funding research at the station included the U.S. Department of Energy, NASA, the Canadian Department of Fisheries and Oceans and the Japanese government.
- The coldest temperature recorded at the station was about - 42 C on New Year's Eve. The warmest was 0.8 C on July 20, 1998.
- Throughout the year, there were occasional visits by polar bears. The largest number of bear sightings occurred in the interval between mid-May and late June. It is estimated that at least 10 different bears were sighted in the vicinity of the station. A family comprising a mother with two cubs stayed in the general area of the station for 1 1/2 weeks.
- One example of the problems with current climate models of the Arctic: Current models of the Arctic climate can give vastly different results when considering various scenarios. For instance, some models say doubling the amount of carbon dioxide in the earth's atmosphere (something scientists feel is likely to happen within the next 50 to 100 years) will make the Arctic ice pack half as large as it is today. Others predict it will disappear completely.
- Instruments used at Ice Station SHEBA ranged from simple meter sticks stuck in the snow to a state-of-the-art cloud LIDAR that monitored clouds by scanning a laser across the sky. Sensors were hung from tethered balloons and were mounted on three different metal towers, the ship deck and on the ice.
- Mother Nature rearranged parts of the station on numerous occasions during the winter. For example, it took a mere 15 minutes for two pieces of ice to come together at the bow of the ship with enough force to push up a 10-foot tall ridge of ice. Teetering half on and half off the ridge was a cold-weather tent housing three snowmobiles. Everyone, from crew to scientists to cooks, went to work with ropes and pulleys to lower the snowmobiles down from the ridge that continued moving and buckling while everyone concentrated on the task at hand.
- Summer brought a slowly rising flood of melt ponds, open water and soft surfaces. The team that was used to riding snowmobiles to their work areas half a mile from the ship, went from riding to walking the distance, to having to build snow bridges over soft parts so they could walk, to using a row boat to traveling by helicopter - all in a matter of weeks. That same group once got a call on the radio from a group at work on a different part of the floe saying they'd just seen one of their stations float by.
(Note: Media outlets can obtain high-resolution images from SHEBA by calling Sandra Hines, University of Washington)
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