Physical processes and biogeochemistry of particle fluxes over the Beaufort slope and in Canada Basin




O'Brien, Mary C.

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Sedimentation rates and compositions of sinking particles were investigated at three sites on the Beaufort slope and one in Canada Basin during the period 1990-1994 using moored sequential sediment traps. A method was developed to identify the terrigenous and biogenic components of the fluxes. The physical context including ice cover, ocean currents, river inputs, winds, air temperature, incident light, and nutrient availability provide essential information to the interpretation of the particle fluxes and to the understanding of shelf-basin sediment transport in this area. Eddies, internal waves, upwelling and downwelling, and the state of the ice cover all played important and overlapping roles in the pattern of observed fluxes. A peak in the flux of highly terrigenous material under complete ice cover in mid-winter to the northwest of Mackenzie Trough was associated with predominantly downwelling conditions and the passage of a series of eddies and internal waves. A prolonged spring diatom bloom occurred in the mid-slope area and was clearly associated with an early opening of the ice on the east side of the shelf. Higher fluxes at the Canada Basin site were associated with a large eddy clearly identifiable from the current-T-S record and also from the composition of the suspended material carried with it. At the base of the slope (2700 m), the composition was highly terrigenous and remarkably consistent. Higher up the slope (700 m), biogenic peaks in the summer diluted the terrigenous material briefly, but it appears that there is a constant background of highly terrigenous material. There was a high degree of variability between sites and over the slope there was not enough data to asses the inter-annual variability. In Canada Basin, the inter-annual variability was closely linked to the extent of open water in the summer period. At all sites, lateral transport is clearly indicated by the increase in flux with depth. The data robustly demonstrate the need for detailed knowledge of physical processes for informed interpretation of particle fluxes and sediment transport in this area.



Arctic, shelf, sediment trap, sediment, particulate, transport, flux, terrigenous, biogenic, carbon, nitrogen, silica, aluminum, isotope, d13C, d15N, eddies, eddy, upwelling, downwelling, internal waves, shelf-basin, biological production, diatom, bloom, ice-edge, resuspension, currents, temperature, salinity, nutrients, resuspension, nepheloid