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<p>The unique properties of the temperature and salinity profiles for polar oceans are critical for high-latitude mixed layer thermodynamics. In the Polar regions the water column is coldest and freshest at the surface where ice may be present. This density structure often leads to entrainment and affects both the mixed layer depth and the ice thickness. Thermobaricity, the combined dependence of seawater thermal expansion on temperature and pressure, magnifies the buoyancy flux associated with mixed layer convection. When thermobaricity amplifies entrainment so that the heat into the mixed layer is greater than the heat leaving the water column, the mixed layer warms and any existing ice begins to melt. Similarly, if the heat entrained is less than the heat leaving the column, the mixed layer cools and freezing occurs at the surface. In the former situation a polynya, or region of no ice surrounded by ice coverage, may form. A one-dimensional vertical model is built, and trial cases are run to show the intricate relationships that govern the heat and salt fluxes and subsequent ice thickness. The model shows the importance of thermobaricity to the air-sea-ice interactions. It also offers significant insight into how relatively constant atmospheric forcing can lead to polynya-like conditions.
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<br>Subjects: Polynyas; Sea ice</div>
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Roth, Mathias K.</div>
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