Measurements to parameterizations: mixing in the open and coastal oceans

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Ocean mixing is a crucial component of the earth system, driving heat downwards, mixing nutrients upwards, and energizing ocean circulations from coastal to global scales. Quantifying, characterizing, and predicting ocean mixing is a daunting task given the spread of spatial and temporal scales that must be resolved. Our group makes innovative measurements of ocean mixing and develops simplified ocean-physics simulations that elucidate the mixing mechanisms. The combination of observations and simulation in one group is rare internationally.******We propose to focus on four mixing processes. The first is to measure lateral stirring processes in the North East Pacific using our undulating Moving Vessel Profile and a ship's current profiler. As numerical models start to resolve mesoscale eddies we need new parameterizations of submesoscale processes to make sure these models mix eddy-borne heat and nutrients properly in the upper ocean. The NE Pacific is a good laboratory to measure these processes, as the warm California Undercurrent mixes laterally with the cold Alaskan gyre. Our measurements will help set the baseline for future parameterization of this mixing in models being developed by Bedford Institute of Oceanography.******The second process is mixing at abrupt topography. We have developed a parameterization for tidally generated turbulence over isolated bathymetry. However, before this work is useful for large-scale simulations, we must extend its use to more complicated bathymetry. This will involve new simulations in both two and three dimensions, and will make exciting student theses.******The third process is to numerically confine a tidal energy budget in Knight Inlet, a coastal fjord. Tidal energy budgets over isolated topography like the sill in Knight Inlet or Hawaii indicate that much of the energy lost from the surface tide radiates away as internal tides. No one has closed a credible budget indicating where that energy eventually dissipates. We propose to do this for a high-resolution simulation of Knight Inlet simply because it is well-confined, and I hope that we can verify the mechanisms in future field programs.******Finally, I propose to carry on the work of graduate student Ken Hughes, examining the role of mixing and hydraulic flows in controlling the flow of fresh Arctic Ocean water through the Canadian Arctic Archipelago and into the North Atlantic. Recent large-scale models overestimate the transport of these flows by up to 80%, indicating missing physics in those models. We will carry out high-resolution nested simulations of the flow through these channels, including the effect of ice, and working with large-scale modellers to parameterize the form drag due and mixing on the flow due to underresolved hydraulic flows.******While many of these problems are local to Canada, they all have relevance to better understanding globally important mixing processes.