HR: 0800h
AN: OS41A-0465    [Abstracts]
TI: Dissolved Oxygen Extrema in the Arctic Ocean Halocline from the North Pole to the Lincoln Sea
AU: * Falkner, K K
EM: kfalkner@coas.oregonstate.edu
AF: College of Oceanic & Atm Sciences, Oregon State University, 104 Ocean Admin Bldg, Corvallis, OR 97331-5503 United States
AU: Steele, M
EM: mas@apl.washington.edu
AF: Applied Physics Laboratory University of Washington, 1013 NE 40th Street, Seattle, WA 98105-6698 United States
AU: Woodgate, R A
EM: woodgate@apl.washington.edu
AF: Applied Physics Laboratory University of Washington, 1013 NE 40th Street, Seattle, WA 98105-6698 United States
AU: Swift, J H
EM: jswift@odf.ucsd.edu
AF: UCSD Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0214 United States
AU: Aagaard, K
EM: aagaard@apl.washington.edu
AF: Applied Physics Laboratory University of Washington, 1013 NE 40th Street, Seattle, WA 98105-6698 United States
AU: Morison, J
EM: morison@apl.washington.edu
AF: Applied Physics Laboratory University of Washington, 1013 NE 40th Street, Seattle, WA 98105-6698 United States
AB: Dissolved oxygen profiling by new generation sensors was conducted in the Arctic Ocean via aircraft during May 2003 as part of the North Pole Environmental Observatory (NPEO) and Freshwater Switchyard (SWYD) projects. At stations extending from the North Pole to the Lincoln Sea north of Ellesmere Island, such profiles display what appear to be various oxgyen maxima (with concentrations 70 percent of saturation or less) over depths of 70 to 110 m in the halocline, corresponding to salinity and temperature ranges of 33.3-33.9 and -1.7 to -1.5 deg C. The features appear to be widely distributed: Similar features based on bottle data were recently reported for a subset of the1997-1998 SHEBA stations in the southern Canada Basin and in recent Beaufort Sea sensor profiles. Oxygen sensor data from the August 2002 Chukchi Borderlands (CBL) and 1994 Arctic Ocean Section (AOS) projects suggest that such features arise from interleaving of shelf-derived, oxygen depleted waters. This generates apparent oxygen maxima in Arctic basin profiles that would otherwise trend more smoothly from surface near-saturation at the surface to lower concentrations at depth. For example, in the Eurasian Basin, relatively low oxygen concentrations are observed at salinities of about 34.2 and 34.7. The less saline variant is identified as part of the lower halocline, a layer originally demarcated by a Eurasian Basin minimum in "NO", reinforced by additional inputs in the Canada Basin. The more saline and thus denser variant appears to arise from transformations of Atlantic source waters over the Barents and/or Kara shelves. Other low-oxygen waters are generated in the vicinity of the Chukchi Borderlands, from Pacific shelf water outflows that mix into Eurasian waters that entered the Makarov Basin over the Lomonosov Ridge. One such input is associated with the well-known silicate maximum that historically has been associated with a salinity of about 33.1. Above that (32-33 salinity range), there is a layer moderately elevated in temperature (summer Bering Sea water) that we show is also oxygen depleted. We propose that these low oxygen waters influence the NPEO and SWYD profiles to varying extents in a manner reflective of the large-scale circulation. The patterns of halocline circulation we infer from the intrusive features defy a simple boundary-following cyclonic flow. These results demonstrate the value of the improved resolution made feasible with continuous oxygen profiling. In the drive to better understand variability and change in the Arctic Ocean, deployment of appropriately calibrated CTDO packages offers the promise of important new insights into circulation and ecosystem function.
DE: 4808 Chemical tracers
DE: 4894 Instruments and techniques
DE: 4207 Arctic and Antarctic oceanography
DE: 4283 Water masses
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting