Space & time variability of pan-Arctic estimates of internal wave-driven dissipation, mixing, and heat fluxes inferred from the Ice-Tethered Profiler network

Melanie Chanona, University of British Columbia, Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada, Hayley V Dosser, University of Washington Seattle Campus, Seattle, WA, United States, Stephanie Waterman, University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada, Nicole Shibley, Yale University (at abstract submission), Earth & Planetary Sciences, New Haven, CT, United States and Mary-Louise Timmermans, Yale University, Department of Geology and Geophysics, New Haven, United States
Quantifying mixing rates in the Arctic Ocean is critical to our ability to predict heat flux, freshwater distribution, and circulation. However, turbulence measurements in the Arctic are sparse, and cannot characterize the high spatiotemporal variability typical of ocean mixing. Using year-round temperature and salinity data from Ice-Tethered Profiler (ITP) instruments between 2004 and 2018, we apply a finescale parameterization to obtain pan-Arctic estimates of turbulent dissipation and mixing rates at unprecedented space-time resolution. Building on previous work that used ITP data to identify double-diffusive staircases and analyze the associated convective mixing, we apply the finescale parameterization only where these step-like thermohaline structures are not present and mixing is expected to be internal wave-dominated. We find that the inferred wave-driven dissipation and mixing rates are generally low, but highly variable in both space and time, displaying significant regional differences between the shelves and central basins, as well as a small seasonal cycle. We detect no statistically significant interannual trend in mixing rate estimates over the period examined, with the exception of a small increase in the Canada Basin immediately below the mixed layer. The joint consideration of turbulent dissipation rates and stratification imply varied Arctic Ocean mixing regimes, which are most often not appropriately characterized as isotropic turbulence. Where justified, we infer turbulent heat fluxes out of the Atlantic Water layer that are mostly small, but also exhibit a distinct regional dependence.