HR: 0800h
AN: OS41B-0598    [Abstracts]
TI: Observation and Simulation of Deep Water Renewal in Foxe Basin, Canada
AU: * Defossez, M
EM: marc.defossez@uqar.qc.ca
AF: Institut des Sciences de la Mer, Université du Québec … Rimouski, 310, allée des Ursulines, Rimouski, QC G5L 3A1 Canada
AU: Saucier, F J
EM: francois_saucier@uqar.qc.ca
AF: Institut des Sciences de la Mer, Université du Québec … Rimouski, 310, allée des Ursulines, Rimouski, QC G5L 3A1 Canada
AU: Myers, P G
EM: pmyers@ualberta.ca
AF: Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E3 Canada
AU: Caya, D
EM: caya.daniel@ouranos.ca
AF: Ouranos, 550, rue Sherbrooke Ouest 19e étage, tour Ouest, Montréal, QC H3A 1B9 Canada
AB: New yearlong salinity and temperature time series observations from a mooring deployed in August 2003 at 440 m depth in Foxe Channel (65.1°N, 81.3°W) exhibit a strong seasonal cycle. This cycle can be roughly divided into three intervals, first an abrupt arrival of near freezing and saline waters occurring at the beginning of April characterized by a temperature drop from -1.65°C to -1.95°C over 5 days, and a salinity jump from 33.32 to 33.75 PSU over one month, subsequently a two month period over which the properties do not change significantly, and finally a progressive freshening and warming during fall and winter (reaching -1.65°C and 33.32 PSU). The results of a detailed sea ice-ocean-atmosphere regional climate model reproduce these observations and are used to examine the sources, variability and fate of these water masses in the Foxe Basin / Hudson Bay / Hudson Strait system. The model shows that the seasonal component is not due to winter mixed layer deepening, as that only reaches a depth of approximately 85 m, it is instead associated with the horizontal circulation of new dense waters produced through brine rejection near shore in the shallower northwestern Foxe Channel. The computed down slope mean current is 7 cm/s during the dense waters production period, and Lagrangian tracer experiments confirm that the dense waters produced there (near 66.3°N, 83.1°W) are advected to the deep trough in about 20 days. Between April 10 and September 11, the mean estimated southeastward transport of dense waters is 0.1 Sv with peaks reaching 0.4 Sv. The volume of produced dense waters corresponds to about 4 times the prism below 300 m depth in Foxe Channel. Eulerian tracer experiments show that the dense waters circulate around the east of Southampton Island to disperse and partly renew the deep waters in Hudson Bay. The model suggests that no dense waters enter the bay through Roes Welcome Sound because of the presence of a sill at 60 m depth limiting exchanges with Foxe Basin. The amount of dense waters also formed in northwestern Hudson Bay polynya is compared with the inflowing contribution from Foxe Basin. The role of tidal mixing and sea ice cover dynamics is investigated through sensitivity experiments.
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4243 Marginal and semi-enclosed seas
DE: 4255 Numerical modeling (0545, 0560)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005