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A cruise during autumn freeze-up in the western Arctic Ocean

By Robert S. Pickart

Newly forming ice on the Beaufort shelf, which drives the formation of winter water. At this time of year, the sun stays close to the horizon throughout the day. Photo by A. Pacini.

R/V Sikuliaq, one of the two ice breakers in the US fleet, is presently carrying out a 33-day cruise to the Beaufort and Chukchi Seas in the western Arctic Ocean. The project aims to better understand the fate of the Pacific water that flows northward through Bering Strait, including its impact on the regional ecosystem. The first priority on the cruise is to turnaround a mooring that has been maintained in the boundary current of the Beaufort Sea since 2002. The mooring monitors the flow of Pacific water and also measures the shelf-basin exchange of water and properties driven by storms. Additionally, the mooring is equipped with biochemical sensors and a passive acoustic device that measures marine mammal calls, including those of bowhead whales which migrate through the region. The second aim of the cruise is to carry out a broad-scale survey of the boundary current system of the Chukchi and Beaufort Seas. This year the cruise is taking place late in the season during the fall freeze-up. As such, we are obtaining a rare view of winter water formation on the Beaufort shelf due to brine-driven convection as the ice forms. There is also a host of interdisciplinary ancillary projects being carried out on the cruise by international investigators. This includes sediment sampling, underway isotope measurements of the water and air, and sampling for black carbon.

The cruise is funded by the National Science Foundation’s Office of Polar Programs, as part of the Arctic Observing Network.

The ship navigates through leads and regions of light ice cover as it transits between stations. Photo by A. Pacini.

Lowering the Conductivity-Temperature-Depth instrument package into ice infested waters. Much of the operations occurred in darkness and snow. Photo by A. Kowalski.