The Impact of Submesoscale Dynamics on Arctic Freshwater Fronts

Marion S Alberty, Princeton University, Princeton, United States; NOAA Geophyscial Fluid Dynamics Laboratory, Princeton, NJ, United States, Sonya Legg, Princeton University, Princeton, NJ, United States, Robert Hallberg, NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, United States, Jennifer A MacKinnon, UC San Diego, Scripps Institution of Oceanography, La Jolla, United States, Janet Sprintall, University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States; Scripps Institution of Oceanography, La Jolla, United States, Matthew H Alford, Scripps Institution of Oceanography, UC San Diego, La Jolla, United States; University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, John Mickett, University of Washington, Applied Physics Laboratory, Seattle, United States and Elizabeth Fine, Scripps Institution of Oceanography, La Jolla, CA, United States
Abstract:
The seasonal melting of sea ice is a source of freshwater in the Arctic which can create a cool, fresh layer, insulating sea ice from the underlying warmer, saltier mixed layer. At the same time, the lateral buoyancy gradients produced by this freshwater flux provide a source of available potential energy which, through submesoscale instability, can enhance lateral and vertical fluxes of salt and heat across the interface between the meltwater layer and the surface mixed layer. We present novel, high-resolution observations of upper ocean dynamics in the Beaufort Gyre from two September cruises. These observations indicate a significant, positive relationship between the strength of submesoscale lateral gradients and turbulent mixing in the upper ocean. Motivated by these results, we initialize numerical simulations using our observations of a sharp, freshwater front and analyze the output to investigate the role of submesoscale dynamics in upper Arctic ocean heat and salt budgets. We compare heat and salt budgets for simulations which resolve both submesoscale and mesoscale dynamics, and coarser resolution simulations which only capture the mesoscale, highlighting the importance of the submesoscale-induced buoyancy flux. We also compare the resolved submesoscale buoyancy fluxes to estimates based on current parameterizations. Finally the relationship between the surface freshwater flux and the strength and persistence of the submesoscale dynamics are investigated for a range of realistic surface forcing.
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