University of Hokkaido ‐ SICOPOLIS

Model description

SICOPOLIS ("SImulation COde for POLythermal Ice Sheets") is a dynamic/thermodynamic ice-sheet model that has been developed continuously since more than 25 years. It has been applied to problems of past, present and future glaciation of Greenland, Antarctica, the entire northern hemisphere, the polar ice caps of the planet Mars and others (> 140 publications in the peer-reviewed literature). The model supports the shallow-ice, shelfy-stream and shallow-shelf approximations as well as hybrid shallow-ice–shelfy stream dynamics. Thermodynamics solvers include enthalpy, polythermal and cold-ice schemes. The model is coded in Fortran, based on a consequent ease-of-use philosophy, and it is available to the scientific community as free and open-source software (http://www.sicopolis.net).

Calving implementation

Currently, SICOPOLIS only supports (1) ice-shelf calving via a prescribed threshold thickness at the front, (2) grounded marine-ice calving via a parameterization for "underwater-ice" calving (Dunse et al. 2011), and (3) both types of calving via prescribed ISMIP6-type retreat masks (Goelzer et al. 2020, Seroussi et al. 2020). Implementation of further calving schemes is under development.

Experiments

Calving Algorithm 1 (fixed calving front position)

We conduct this experiment with ice-free initial conditions, 5 km horizontal resolution, a constant surface mass balance of 0.3 m a⁻¹, a constant surface temperature of −10°C, a geothermal heat flux of 42 mW m⁻², a Weertman-Budd-type sliding law with exponentially decreasing sub-melt sliding (C = 1 m a⁻¹ Pa⁻¹, p = 3, q = 2, γ_sms = 1 K) , hybrid shallow-ice–shelfy stream dynamics and an enthalpy method for thermodynamics.

Within the 5000 model years, the system evolves into a quasi-steady state. However, due to the thermomechanical coupling, some oscillations persist.

Fig. 1. Calving Algorithm 1 (fixed calving front position): Simulated ice thickness. Thick solid line: calving front, thin solid line: grounding line.

 

Fig. 2. Calving Algorithm 1 (fixed calving front position): Simulated surface velocity. Thick solid line: calving front, thin solid line: grounding line.

 

Fig. 3. Calving Algorithm 1 (fixed calving front position): Simulated calving rate.