Abstract:

Submesoscale flows, occurring at scales of about 1–10 km, are crucial to the vertical transport of heat and other tracers in the upper ocean. These flows are energized by instabilities that extract potential energy from lateral buoyancy gradients, which are ubiquitous in the seasonal sea ice zone. Process studies have shown that submesoscale flows influence sea ice mechanics and thermodynamics. However, it is necessary to quantify the spatiotemporal distribution of submesoscale fluxes in order to upscale their impact. Here, we utilize hydrographic data from seal-borne sensors to demonstrate that the Southern Ocean seasonal ice zone can be separated into three regimes of submesoscale flux variability, which are associated with distinct dominant drivers. Furthermore, the magnitude and sign of the mean heat fluxes in these regimes differs, which dictates their influence on the upper-ocean heat budget, mixed-layer depth, and sea ice properties.

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