Woods Hole Oceanographic Institution

Claudia Cenedese

»Downwelling in Basins Subject to Buoyancy Loss
»Entrainment and mixing dynamics of surface-stress-driven stratifi ed flow in a cylinder
»Laboratory experiments on two coalescing axisymmetric turbulent plumes in a rotating fluid
»Impact of fjord dynamics and glacial runoff on the circulation near Helheim Glacier
»The relationship between flux coefficient and entrainment ratio in density currents
»A new parameterization for entrainment in overflows
»Laboratory experiments on the interaction of a buoyant coastal current with a canyon: application to the East Greenland Current
»Variations in ocean surface temperature due to near surface flow: straining the cool skin layer
»Mixing in a density-driven current flowing down a slope in a rotating fluid
»Laboratory experiments on mesoscale vortices colliding with an island chain
»Laboratory observations of enhanced entrainment in dense overflows in the presence of submarine canyons and ridges
»How entraining density currents influence the stratification in a one-dimensional ocean basin
»Laboratory experiments on eddy generation by a buoyant coastal current flowing over variable bathymetry
»Laboratory experiments on mesoscale vortices interacting with two islands
»Variability of Antarctic bottom water flow into the North Atlantic
»Laboratory experiments on a mesoscale vortex colliding with topography of varying geometry in a rotating fluid
»A laboratory model of thermocline depth and exchange fluxes across circumpolar fronts
»A dense current flowing down a sloping bottom in a rotating fluid
»Laboratory experiments on mesoscale vortices colliding with a seamount
»Stability of a buoyancy-driven coastal current at the shelf break
»Eddy-shedding from a boundary current around a cape over a sloping bottom
»Cyclone and anticyclone asymmetry in a rotating stratified fluid over bottom topography

Cenedese C., Downwelling in Basins Subject to Buoyancy Loss, Submitted to J. Phys. Oceanogr., 2011

Recent observational, theoretical, and modeling studies all suggest that the upper part of the downwelling limb of the thermohaline circulation is concentrated in strong currents subject to buoyancy loss near lateral boundaries. This is fundamentally different from the traditional view that downwelling takes place in regions of deep convection. Even when resolving the buoyant boundary currents, coarse resolution global circulation and climate models rely on parameterizations of poorly known turbulent mixing processes. In this study, the first direct measurements of downwelling occurring within a basin subject to buoyancy loss are obtained. Downwelling is observed near the basin’s vertical wall within the buoyant boundary current flowing cyclonically around the basin. Although the entire basin is cooled, downwelling is absent in the basin interior. Laboratory rotating experiments are conducted to explicitly resolve the turbulent mixing due to convective plumes, the baroclinic eddies generated by the boundary current, and identify where downwelling takes place. Hence, in the laboratory small vertical velocities can be measured more reliably than in many numerical calculations, while the measurement of these small vertical velocities is still a challenge for field experiments. Downwelling is observed to occur near the vertical wall within a boundary layer with a thickness that scales with the Rossby radius of deformation, consistent with the dynamical balance proposed by a previous numerical study. Hence, downwelling in the Labrador Sea and Lofoten Basin cyclonic boundary currents may be concentrated in a Rossby deformation thick boundary layer in regions with large eddy generation.

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