Modelling the evolution of an ice sheet's weathering crust

TL;DR

This paper develops a numerical model to study the formation and decay of the weathering crust on ice sheets, revealing how climate variations influence its dynamics and providing insights into future climate change impacts.

Contribution

It introduces a time-dependent thermodynamic model and numerical enthalpy method to simulate weathering crust evolution under varying climate forcings.

Findings

Qualitative agreement with observed crust behaviour

Different dynamics during crust growth and decay

Impact of diurnal and annual heat flux variations

Abstract

The weathering crust is a layer of porous ice that can form at the surface of an ice sheet. It grows and decays in response changing weather and climate conditions, affecting the albedo, the melt rate, and the transport of meltwater across the surface. To understand this behaviour, we seek time-dependent solutions to a continuum, thermodynamic model for the porosity, temperature and thickness of the weathering crust, and the internal and surface melt rates. We find solutions using a numerical enthalpy method, presented in this study. We use idealised `switching' and sinusoidal forcings to explore the different dynamics exhibited during growth and decay, the timescales involved, and the impact of diurnal vs. annual variations. The results demonstrate qualitative agreement with observations, and provide insight into the relative importance of different surface heat fluxes during the growth and decay of the crust. The model therefore provides a useful tool for exploring the response of the weathering crust to climate change.