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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