Ocean convection and mixing: from signature to parameterization

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I request support for continuing research on the dynamics of ocean mixing and watermass exchange. My main interest is in key phenomena that cannot be handled directly by numerical models, owing to coarse model resolution. Dynamically-based parameterizations of such phenomena are needed for reliable numerical simulation of the ocean and climate system.Over the funding period, my research program will build on two themes of great scientific interest and practical importance, one related to ice in the Northwest Passage and the other to watermass interactions on the Scotian Shelf. The work will be carried out with students, and the planned close collaboration with partners in Department of Fisheries and Oceans should contribute greatly to the career potential of the graduates.Theme 1: convective heat fluxes in ice-influenced domainsMy research group will study the effects of ocean turbulence and convection on ice cover in coastal waters, using fine-scale signatures acquired with an advanced profiling instrument deployed in Barrow Strait. This is in the Northwest Passage, so a key initial objective will be to improve on statistical predictions of the periods of ice cover, a prime factor for navigation. By incorporating signatures throughout the water column, the methodology will improve upon previous predictions using point-wise measurements. However, the improvement involves more than mere statistical power. We will also apply results from the turbulence literature to infer heat fluxes, and results from the convection literature to infer ice transformation. Another objective is to relate these things to the background state, to develop more robust predictions of ice cover in the study region. This work will pave the way to improved parameterizations for use in models of general ice-affected regions.Theme 2: inference of lateral interleaving with glider-based instrumentationOcean gliders are used increasingly to observe coastal waters. Their zigzag profiling motion yields high spatial sampling densities that reveal ocean variations that are difficult to resolve with conventional ship-based surveys. We will take advantage of this enhanced resolution to examine fine-scale frontal features on the Scotian Shelf, with a particular focus on cross-frontal exchanges caused by quasi-lateral interleaving. My tests with glider surveys carried out over the past few years suggest the feasibility of tracking interleaving motions and associated hydrographic changes in sufficient detail to provide improved dynamical constraints on parameterizations of cross-frontal exchange. The results will deepen understanding of important issues relating to how the waters of the Nova Scotia current interact with waters derived from the Gulf Stream. The anticipated advances in sampling and analysis methodologies will also benefit studies of the many other coastal regions in which watermasses collide.