Submesoscale Sea Ice‐Ocean Interactions in Marginal Ice Zones

Abstract

Signatures of ocean eddies, fronts, and filaments are commonly observed within marginal ice zones (MIZs) from satellite images of sea ice concentration, and in situ observations via ice‐tethered profilers or underice gliders. However, localized and intermittent sea ice heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea ice forecasts. Here, we explore mechanical sea ice interactions with underlying submesoscale ocean turbulence. We demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along MIZs with spatial scales O(10 km) and Rossby numbers O(1). In low‐wind conditions, cyclonic eddies and filaments efficiently trap the sea ice and advect it over warmer surface ocean waters where it can effectively melt. The horizontal eddy diffusivity of sea ice mass and heat across the MIZ can reach O(200 m2 s−1). Submesoscale ocean variability also induces large vertical velocities (order 10 m d−1) that can bring relatively warm subsurface waters into the mixed layer. The ocean‐sea ice heat fluxes are localized over cyclonic eddies and filaments reaching about 100 W m−2. We speculate that these submesoscale‐driven intermittent fluxes of heat and sea ice can contribute to the seasonal evolution of MIZs. With the continuing global warming and sea ice thickness reduction in the Arctic Ocean, submesoscale sea ice‐ocean processes are expected to become increasingly prominent.

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

“…This effect would further increase the freshwater accumulation in the upper ocean near the filament's center. Different from Manucharyan and Thompson (), the high velocities of the filament extend significantly deeper (≈50 m in Manucharyan & Thompson, versus >250 m here). Meltwater generates shallow horizontal density gradients, whereas the contrast between AW and PW leads to deep reaching horizontal density gradients.…”

“…The locations of dense filaments are presumed to correlate with the accumulation of surfactants at the sea surface since they are positively buoyant and are not subducted by the ASC (McWilliams et al, ). Numerical simulations also indicate that cyclonic eddies and filaments can efficiently trap sea ice (Manucharyan & Thompson, ). Sea ice, unlike surfactants, can be sensed remotely during windy conditions.…”

Wave Attenuation Through an Arctic Marginal Ice Zone on 12 October 2015: 2. Numerical Modeling of Waves and Associated Ice Breakup

“…However, strong mesoscale or submesoscale eddies at the ice edge have been found with velocities up to 1 m/s (Lund et al, ). Similar features have been reproduced in numerical simulations by Manucharyan and Thompson (). Their interaction with ocean waves and sea ice, although possibly important, will not be considered here.…”

Arctic Sea Ice Drift Measured by Shipboard Marine Radar

“…The MIZ, with its spatially variable ice cover and associated strong gradients (e.g., in terms of mixed layer temperature and salinity), is subject to particularly strong air‐sea‐ice interactions and submesoscale (∼100 m to 10 km) upper ocean dynamics (Manucharyan & Thompson, ; McPhee et al, ; Timmermans et al, ). Given the continuous changes in the location of the ice edge and local ice concentration, characteristic time scales are likely on the order of hours.…”