Surface processes and the interior ocean response

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The long term goal of my research program is to understand how different classes of oceanic motion interact. These interactions help to determine both the general circulation of the oceans and the vertical velocities responsible for transporting heat and other tracers through the water column. Understanding them is important both to our theoretical understanding of the oceans and to inform modelling strategies. Most recent work in this area focuses on interactions between geostrophic currents (such as the Gulf Stream, Kuroshio or Antarctic Circumpolar Current) and near-inertial oscillations (NIOs, which oscillate near the Coriolis frequency). The reason for this emphasis is that most of the ocean's kinetic energy resides in these two classes of flow. My work has been influential in helping to clarify how NIOs might affect the energetics of the geostrophic circulation. Both geostrophic currents and NIOs are particularly strong in the surface ocean, which is also home to surface gravity waves, sea ice, and a frictional Ekman layer. Short term goals of my research are to better understand how these processes act to modify geostrophic currents and NIOs. The sea ice and the surface gravity wave fields can be thought of as modifying the effective wind forcing that acts on ocean circulation. Our work will help to clarify these modifications (which can be qualitative in nature in the high wavenumber range). In the case of sea ice, we will be interested in how this effective forcing is likely to evolve as sea ice thins. We will also examine how these changes to the effective forcing influence the evolution of geostrophic turbulence and NIOs. The surface layer is also home to a frictional Ekman layer and recent work (including our own) has shown Ekman transport and pumping to not be determined solely by the local winds and currents, but to instead depend more globally on the forcing and current fields. This, and recently uncovered instabilities involving Ekman-NIO interaction point to a need to better understand these dynamics, and doing so is another of our short term goals. The work proposed will help to disentangle a complex mixture of processes occurring in the upper ocean, and how interactions between them help to determine ocean circulation and the superposed field of NIOs. An outcome is therefore a better understanding of vertical transport velocities transporting CO2, heat, and nutrients into and out of the surface layer and is thus of direct interest to climate and environmental scientists. Our work also helps bridge gaps between different aspects of physical oceanography (e.g., midlatitude versus Arctic ocean circulation theory and better integrating surface waves into GFD) and as such benefits Canadian scientists working in these fields.