Abstract

Co-authors: Pat Langhorne (University of Otago), Natalie Robinson (NIWA), Mike Williams (NIWA)

Thermodynamic ice ablation includes both melting and dissolving of the ice. Existing parametrisations are usually based on the 3-equation model, with equations that describe heat and salt flux balances together with the freezing point equation for sea water. However, these equations do not represent both melting and dissolving conditions, or the transition between these conditions. Nor do the 3 equations represent well the two dominant velocity regimes: shear-driven and buoyancy-driven mixing. Turbulent heat and salt transfer coefficients need to reflect the variety of boundary layer structures that can form under different velocity and temperature regimes.

Here the different conditions and velocity regimes are considered in the in context of multi-year observations of temperature, velocity and ablation rate from under the Ross Ice Shelf. These observations of a dissolving ice shelf in sub-zero conditions can be used to constrain transitions from buoyancy-driven mixing to sheer-driven mixing. While these observations are under an ice shelf they are expected to scale to the higher salinities found in sea ice.