Schedule May 22, 2018
Submesoscale sea ice-ocean interactions in marginal ice zones
G. Manucharyan (Caltech)

Arctic sea ice undergoes a seasonal cycle, causing it to expand in winter and retreat in summer. Observations show that annual sea ice volume has declined in recent decades, and climate models predict that it will continue to do so in decades to come. The ocean dynamics in regions called marginal ice zones (MIZS) - those that contain a mixture of sea ice and open water - can help explain the mechanisms that affect seasonal sea ice dynamics and distribution. Patterns resembling ocean turbulence (unstable swirling and mixing) can be observed in the sea ice in these regions, implying the importance of ice-ocean interactions. Large-scale structures of ocean turbulence are caused by gradients in temperature and salinity that can occur when the upper ocean has spatial differences in heat content. Because heat is stored in the upper ocean, heat transfer (flux) between the ocean and ice is one of the primary mechanisms for enhanced sea ice melt, and can be affected by ocean turbulence. This study explores how the ocean affects sea ice distribution and melt in these regions by using a numerical model that represents ocean eddies (large, turbulent, whirling rings of water), the rotating force of these eddies on the ice, pressure of the ice converging on itself, friction, and heat flux between the ice and ocean. The model shows that cyclonic (counterclockwise rotating) eddies accumulate ice, while anticyclonic (clockwise rotating) eddies repel it. These results suggest that eddies help to expand the MIZs and affect the distribution of ice-ocean heat flux. A large-scale view of the Arctic shows seasonal differences in ocean dynamics affected by ice, which in turn affects the total amount of ice-ocean heat flux in the region. These dynamics are not represented in climate models, but may be important for improving climate forecasts.

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