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