Nonlinear Thermal Transport and Brine Convection in First Year Sea Ice

M.J. McGuinness, H.J. Trodahl , K. Collins, T.G. Haskell

Abstract:

We report the first results from a programme recently set up to directly measure the thermal conductivity of young sea ice.

An array of thermistors frozen into first-year Antarctic sea ice provides temperature against depth data, which is fitted directly with a partial differential equation for heat conduction. Temperatures are recorded every hour at twenty vertical intervals of 100mm over a period of 5 months, allowing accurate and direct estimation of the thermal conductivity. Preliminary results indicate that the thermal conductivity is in the expected range, with some evidence of nonlinear effects deeper in the ice. A larger variance in data is evident at higher temperature gradients and at greater depths in the ice.

Preliminary modelling of the impact of brine migration on heat transport through first-year sea ice is presented. Diffusion-driven brine pocket migration is too slow to contribute significantly to heat flow, but the convective instability of inclined brine slots or tubes is a promising mechanism.

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