A one‐dimensional percolation model of flooding and snow ice formation on Antarctic sea ice

Abstract

A one‐dimensional thermodynamic sea ice growth model is developed with emphasis on seawater flooding and snow ice formation on Antarctic sea ice. To examine the possibility that flooding is the result of brine percolation through a porous ice matrix, and the consequences of this percolation on the salinity structure and mass balance of the ice, flooding is modeled in a semiheuristic fashion by examining two possible regimes for seawater and brine infiltration through the porous ice into the snowpack. A standard model assumes that the upward flow of brine is horizontally homogeneous and brine flow is modeled using a Darcian scheme. A simple model assumes that the infiltrating brine does not interact with the internal ice brine network, but instead percolates upward through cracks, or is restricted in spatial extent. Results of simulations are shown for the climatology in the Ross Sea and compared to field data from one autumn and one winter cruise aboard the R/V Nathaniel B. Palmer in 1995. Sensitivity studies are performed to show the effects of variations in climate forcing. The dependence of brine percolation and snow ice formation on key thermophysical parameters is investigated. Results indicate that the mass balance depends very strongly on the brine flow regime. In the standard model, ice salinities and brine volumes are greatly affected by brine percolation, creating a strong feedback between flooding and future snow ice production. Snow ice formation for the simple model was much more predictable and depended primarily on snow load. Comparison of results with field data indicate that if brine percolation is the major mechanism for flooding and snow ice formation, then there must be either substantial convective redistribution of salt to maintain ice porosity, or the flow must be spatially inhomogeneous.