Scripps scientists participate in historic first surface vessel voyage across Canada Basin

10/31/05

Scientists aboard pioneering icebreaking ships investigate ocean conditions in unexplored region to better understand Arctic's role in global climate change

Two ships taking part in a recently completed research voyage investigating the oceanography, marine geology, geophysics and ice cover of the Arctic Ocean have become the first surface vessels to traverse the Canada Basin, the ice-covered sea between Alaska and the North Pole.

The Swedish vessel Oden and the United States Coast Guard's Healy, both icebreaking vessels outfitted for oceanographic research, completed the historic south-to-north trek in September as part of a recently concluded expedition to explore the marine environment in this unknown region.

Although the same area had been crossed by submarines, the central Arctic Ocean had been Earth's least explored ocean area by surface ships due to its heavy concentration of floating sea ice, which in some areas spans more than 10 feet in thickness.

Jim Swift, a research oceanographer at UCSD's Scripps Institution of Oceanography, participated in the voyage as leader of a five-person team on board Oden that analyzed ocean conditions in an effort to better understand the Arctic's role in the earth's ocean and climate system. Other scientists on board Oden and Healy hailed from Sweden, Finland, Canada, Germany, Norway and Denmark.

According to Swift, part of the reason the Canada Basin surface crossing could be attempted and achieved at this time is because the ice cover over much of the Arctic Ocean has thinned in recent decades, opening the door to surface ships.

"Some indications have shown that the ice volume in the Arctic Ocean has reduced nearly 40 percent since the time submarine transects began more than 40 years ago," said Swift, a scientist in the Physical Oceanography Research Division at Scripps. "There is some scientific debate about the actual percentage but there is no doubt of the thinning in many areas of the region."

Swift's investigations aboard Oden, research funded by the U.S. National Science Foundation Office of Polar Programs, involved examinations of ocean properties to help evaluate recent changes in ocean climate and global change studies. Swift and his team measured the seawater's temperature, salinity and chemical characteristics. Ultimately, the new data will aid assessments of climate change and be used to improve and test scientific models that describe the climate system.

In one example, the new information is already helping scientists decipher how warm water from the Gulf Stream and the Atlantic Ocean circulate in the Arctic Ocean basins. In a case of synergy between geological and oceanographic measurements, scientists using Healy's multi-beam (wide scanning) sonar made maps of the ocean floor over a region of a central Arctic ocean ridge many expected to contain a gap enhancing interchange of deep waters between sub-basins of the Arctic Ocean. At the same time, the Oden science team determined which waters were actually being exchanged, thus partly settling a scientific debate about the deep circulation that underlies the other layers.

"The unique aspect of this cruise was the ability to capture first-time measurements of ocean water across a wide suite of parameters throughout the central Canada Basin," said Swift.

Among the research issues he is addressing, Swift is investigating an Arctic ocean warming signal that emerged in the 1990s in a layer of ocean water, roughly 650- to 2,625-feet deep (200 to 800 meters), and whether the warming is continuing in this decade. Early results from the Oden cruise indicate that the warming was a short-lived burst, or a "pulse," though water temperatures at that depth have not fully receded to pre-1990s measurements.

"Our measurements confirm other recent measurements in showing that the warming was a pulse event rather than a shift," said Swift. "All of the results from the Oden cruise will help tie various measurements together to help us see what the big picture looks like in the Arctic."

In addition to Swift's research in physical and chemical oceanography, researchers from the international team onboard Oden and Healy included biologists investigating organic processes in snow and ice to help identify concentrations of ozone-decomposing compounds in the atmosphere. Other researchers obtained seafloor sediment cores for analysis while others used instruments to survey ocean depths and seismic data.

While ice thinning allowed the historic Canada Basin passage, the two vessels still encountered areas of extremely thick ice, forcing the ships to work in tandem to cut through the ice and forge a passage to the North Pole. Strategic route planning using satellite ice images and frequent helicopter ice reconnaissance aided the navigation. The Oden and Healy reached the North Pole at 9 a.m. (Alaska time) on Sept. 12.

The cruise marked the concluding leg of the Swedish 2005 Beringia Expedition, supported by the Swedish Polar Secretariat. Healy was supported largely by the U.S. National Science Foundation.

Source: Eurekalert & others

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