Edge of the Arctic Shelf
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Seth Flow Diagram
A schematic of the circulation over the Chukchi Sea and Beaufort/Chukchi slope is presented above, showing the three branches of the inflowing Pacific water. These branches are color-coded with navy blue being the most nutrient-rich waters and light blue being the least nutrient-rich. The Siberian Coastal Current (green) is present in summer and fall, but absent or weak in winter and spring. On the continental slope, the Pacific-origin water encounters Atlantic-origin Water (red) which is flowing counter-clockwise around the Arctic basin. Offshore of the slope, in the interior of the Canada Basin, is the clockwise wind-driven flow of the Beaufort Gyre (purple).
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The Expedition - Objectives
Overview | Objectives | Science Crew | The Ship

Our multi-year project, which represents the physical oceanographic component of SBI Phase 2, focuses on understanding the flow of waters from the Bering Sea onto the Chukchi and Beaufort shelves, and the subsequent transferral of these waters into the deep Arctic basin.

Towards this end, in 2002 we deployed two mooring arrays: (1) A widely-spaced array on the Chukchi shelf to measure the three branches of inflowing Pacific-origin water from Bering Strait (indicated by the black stars on the figure), and (2) A high-resolution array on the Beaufort slope to measure exchange processes that transfer the Pacific-origin water to the deep basin (indicated by the black line in the figure). The Chukchi array is a joint University of Washington / University of Alaska (UW/UAF) project, and the Beaufort array is being deployed by the Woods Hole Oceanographic Institution (WHOI).

In Fall 2003, we successfully recovered the moorings and retrieved 14 months of oceanographic data. We then put the moorings back into the water, where they have been collecting data since October 2003. In addition to the mooring work, we also completed 321 scientific stations.

The primary objective of our 2004 cruise (click here for tentative cruise plan) on the USCGC Healy is to recover the 15 moorings, which are located in four regions: the central Chukchi shelf, the Chukchi shelfbreak, Barrow Canyon, and the Beaufort shelfbreak. In addition to this we will do CTD transects throughout the area. The transects will include VPR casts and net tows. Finally, we will attempt to sample eddy features using expendable instruments (XBT, XCTD) as well as CTD casts. For more detailed information on the instruments we'll be using, visit the science page.

UW/UAF project - “The fate of a large and strongly forced Arctic shelf outflow: Physical and biochemical process studies”.

  1. To quantify the characteristics of the shelf flow in the Chukchi Sea (e.g. transport, temperature, salinity), and to determine which upstream processes are principally responsible for the variability of these characteristics.

  2. To quantify the variability of the system on seasonal and interannual timescales, and to assess what might be the connections with a changing climate.

  3. To provide the temporal context of the Chukchi shelf water properties and flows that will be essential for other SBI investigators who are addressing the regional biochemical and physical processes.
WHOI project - “Dynamics of exchange in the Beaufort Sea boundary current system: Implications for interior ventilation”.

  1. To quantify the mean and seasonally varying transport, structure, and water mass content of the boundary current system downstream of the Chukchi Sea outflow points.

  2. To determine the nature and cause of the mesoscale variability of the boundary current, and assess the impact of the variability on the cross-stream exchange of mass and properties.

  3. To identify the dynamics of the secondary circulation.

  4. To elucidate the source of the eddies in the interior western Arctic by comparing the seasonally changing boundary current water to the observed characteristics of the mid-basin eddy field.
These two projects together will improve our understanding of the fate of Pacific-origin water in the western Arctic, and its impact on the ventilation of the interior basin. The physical data will also provide an important context for the biochemical measurements being carried out as part of SBI.