Preprints
https://doi.org/10.5194/egusphere-2025-4718
https://doi.org/10.5194/egusphere-2025-4718
26 Sep 2025
 | 26 Sep 2025
Status: this preprint is open for discussion and under review for Ocean Science (OS).

Seasonal impact of submesoscale eddies on the ocean heat budget near the sea ice edge

Lily Greig and David Ferreira

Abstract. Oceanic submesoscale mixed layer eddies (SMLEs), with horizontal scales of 0.1–10 km, are not captured in climate models. SMLEs energized in the marginal ice zone (MIZ) have been shown to be of importance to sea ice melt rates in summer and to sea ice transport through notably a dynamical coupling with sea ice. Here our focus is on the thermodynamical coupling, which has received comparatively little attention. We aim to quantify, for the first time, the impact of eddies on both sea ice and the heat budget in the MIZ, contrasting different seasons and different background stratifications.

To this end, we set up SMLE-resolving simulations of the ocean mixed layer (ML) near the ice edge using the MITgcm, representing a lead or the MIZ. We isolate the effect of eddies by comparing 3D simulations with eddies to 2D (latitude-depth) simulations without eddies.

In summer (i.e., melting conditions) and regardless of the background stratification, SMLEs act as a heat pump from the atmosphere over the open ocean to the sea ice. On average over a season, SMLEs triple the meridional heat transport to the ice covered region, increase melting over their meridional extent, and trigger a positive radiative feedback by increasing shortwave absorption over the thinner ice. These changes are in the range 20–60 % for reasonable choices of shortwave forcing and initial ice thickness. In winter (i.e., freezing conditions), SMLEs have a relatively small impact on sea ice growth due to compensation between vertical and horizontal eddy heat transports. However, they reduce ML deepening by 80/50 % in the open/ice-covered ocean. Overall, our results reveal up to order one impacts of SMLEs on the heat and sea ice budgets in the MIZ, which will require the development of a SMLE parameterization tailored for polar regions.

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Lily Greig and David Ferreira

Status: open (until 21 Nov 2025)

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Lily Greig and David Ferreira
Lily Greig and David Ferreira

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Short summary
Submesoscale eddies in the ocean (0.1–10 km) are often missing from global climate models, yet they impact nutrient transport, sea ice coverage, and ocean overturning. Using submesoscale-resolving simulations, we show that these eddies near the sea ice edge impact air-sea heat fluxes, ice cover, and ocean heat storage in summer, and mixed layer depth in winter. These findings highlight the need to better represent submesoscale eddies in sea ice – covered regions of global climate models.
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