The sensitivity of landfast sea ice to atmospheric forcing in single-column model simulations: a case study at Zhongshan Station, Antarctica

Single-column sea ice models are used to focus on the thermodynamic evolution of the ice. Generally, these models are forced by atmospheric reanalysis in the absence of atmospheric in situ observations. Here we assess the sea ice thickness simulated by a single-column model (ICEPACK) with in situ observations obtained off Zhongshan Station for the austral winter of 2016. In the reanalysis, the surface air temperature is about 1 degrees C lower, the total precipitation is about 2 mm d(-1) greater, and the surface wind speed is about 2 m s(-1) higher compared to the in situ observations. We designed sensitivity experiments to evaluate the simulation bias in sea ice thickness due to the uncertainty in the individual atmospheric forcing variables. Our results show that the unrealistic precipitation in the reanalysis leads to a bias of 14.5 cm in sea ice thickness and 17.3 cm in snow depth. In addition, our data show that increasing snow depth works to gradually inhibit the growth of sea ice associated with thermal blanketing by the snow due to changing the vertical heat flux. Conversely, given suitable conditions, the sea ice thickness may grow suddenly when the snow load gives rise to flooding and leads to snow-ice formation. However, there are still uncertainties related to the model results because superimposed ice and snowdrift are not implemented in the version of the ice model used and because snow-ice formation might be overestimated at locations with landfast sea ice.

Automated summary

This study uses a single-column sea ice model to simulate the sea ice thickness in the Antarctic winter of 2016 and compares it with in situ observations. The results show that the precipitation in the atmospheric reanalysis has a significant impact on the sea ice thickness, while increasing snow depth inhibits the growth of sea ice.