British Geological Survey, United Kingdom

A fundamentally new multiple-vessel approach was developed under the auspices of the Ocean Drilling Program and the Integrated Ocean Drilling Program (IODP) to drill and recover deeply buried sediments in the Arctic Ocean. This approach overcame the difficulty of maintaining position over a drill site and recovering sediments in waters that are covered in moving ice floes. In August 2004, a convoy of three icebreakers met at the ice edge, northwest of Franz Josef Land, and headed north to begin the Arctic Coring Expedition, IODP Expedition 302. This expedition successfully recovered core at depths >400 meters below seafloor in 9/10 ice-covered water depths ranging from 1100 to 1300 m. Expedition 302 involved >200 people, including scientists, technical staff, icebreaker experts, ice management experts, ships' crew, and educators. At the drill site, temperatures hovered near 0 degrees C and occasionally dropped to -12 degrees C. Ice floes 1-3 m thick blanketed 90% (i.e., >9/10 ice cover) of the ocean surface, and ice ridges, several meters high, were encountered where floes converged. The ice drifted at speeds of up to 0.3 kt and changed direction over short time periods, sometimes within 1 h. A Swedish diesel-electric icebreaker, the Vidar Viking was converted to a drill ship for this expedition by adding a moonpool and a geotechnical drilling system capable of suspending >2000 m of drill pipe through the water column and into the underlying sediments. Two other icebreakers, a Russian nuclear vessel, the Sovetskiy Soyuz, and a Swedish diesel-electric vessel, the Oden protected the Vidar Viking by circling "upstream" in the flowing sea ice, breaking the floes into smaller pieces that wouldn't dislodge the drilling vessel >75 m from a fixed position. Despite thick and pervasive ice cover, the fleet and ice management teams successfully enabled the drilling team to recover cores from three sites. Ice conditions became unmanageable only twice, forcing the fleet to retrieve the pipe and move away until conditions improved. The scientific results from this drilling will significantly advance our understanding of Arctic and global climate.