A Modified Thermodynamic Sea Ice Model and its Application
Originated from Winton’s three-layer model framework, this new sea ice model includes several improvements in the vertical thermodynamics: (1) the number of ice layers increases from two to three; (2) the snow heat capacity is included; (3) a vertically varying salinity profile is implemented; and (4) a temperature- and salinity-dependent heat conductivity parameterization scheme is introduced. A non-iterative, fully implicit time-stepping scheme like Winton’s model is used to calculate the temperature of ice and snow. Results from a series of one-dimensional experiments show that equilibrium ice thickness in the modified model is increased by 45 cm when compared with the original Winton’s model. All modifications mentioned above contribute to this change in ice thickness, among which the increase of ice layer has the most significant effect. Experiments using the Modular Ocean Model version 4 (MOM4) coupled with the modified model show an improved sea ice simulation which includes an increase in both the sea ice volume and thickness over the entire Arctic region, confirming the above founding. However, contrary model behavior exhibits when the snow heat capacity is considered that warrants further investigation.
This study aims to improve the performance of the sea ice model used in MOM4. By adding an additional sea ice layer and a few improvements in model physics, we show improved performance of the model in simulating the sea ice properties.
Summary
This paper presents a modified thermodynamic sea ice model based on Winton’s three-layer model framework. Several improvements focused on vertical thermodynamics have been made in the model. Results from a series of one-dimensional experiments show that equilibrium ice thickness in our modified model is increased by about 45 cm when compared with the original Winton’s model. Sensitivity tests indicate that all modifications mentioned above contribute to this change in ice thickness, among which the increase of ice layer has the most significant effect, followed by the sea ice conductivity parameterization. The modified thermodynamic sea ice model is then coupled into the sea ice component SIS in GFDL MOM4 to exert long-term integration experiments forced by CORE2.0 data. Results indicate that the modified model shows significant improvement in simulating the Arctic sea ice, including an increase in both the sea ice thickness and volume over the whole Arctic region. This confirms the above founding from 1-D simulations.