Comparison of thermodynamics solvers in the polythermal ice sheet model SICOPOLIS

TL;DR

This paper compares four thermodynamics solvers in the SICOPOLIS ice sheet model, evaluating their accuracy and ease of implementation in modeling the thermal structure and cold-temperate transition surface of polythermal ice sheets.

Contribution

It introduces two new one-layer enthalpy schemes and assesses their performance against existing methods in simulating ice sheet thermodynamics.

Findings

ENTM accurately tracks the cold-temperate transition surface.

COLD and ENTC schemes fail to produce continuous temperature gradients.

ENTC and ENTM are viable, easier alternatives to the POLY scheme.

Abstract

In order to model the thermal structure of polythermal ice sheets accurately, energy-conserving schemes and correct tracking of the cold-temperate transition surface (CTS) are necessary. We compare four different thermodynamics solvers in the ice sheet model SICOPOLIS. Two exist already, namely a two-layer polythermal scheme (POLY) and a single-phase cold-ice scheme (COLD), while the other two are newly-implemented, one-layer enthalpy schemes, namely a conventional scheme (ENTC) and a melting-CTS scheme (ENTM). The comparison uses scenarios of the EISMINT Phase 2 Simplified Geometry Experiments (Payne and others, 2000, J. Glaciol. 46, 227-238). The POLY scheme is used as a reference against which the performance of the other schemes is tested. Both the COLD scheme and the ENTC scheme fail to produce a continuous temperature gradient across the CTS, which is explicitly enforced by the ENTM scheme. ENTM is more precise than ENTC for determining the position of the CTS, while the performance of both schemes is good for the temperature/water-content profiles in the entire ice column. Therefore, the one-layer enthalpy schemes ENTC and ENTM are viable, easier implementable alternatives to the POLY scheme with its need to handle two different numerical domains for cold and temperate ice.