How much does Antarctic landfast ice affect coastal polynyas?

Abstract

The coastal polynyas of the Southern Ocean play a crucial role in the formation of dense water and have an impact on the stability of ice shelves. Therefore, it is important to accurately simulate them in climate models. To achieve this goal, the relationship between grounded icebergs, landfast ice, and polynyas appears to be central. Indeed, grounded icebergs and landfast ice are the main drivers of coastal polynyas. However, we do not fully understand how much Antarctic landfast ice impacts coastal polynyas in the model. Moreover, at a circumpolar scale, there are no observations of grounded icebergs available. To address these gaps in knowledge, we conducted a study using the global ocean--sea ice model NEMO4.2-SI³ at a 1° resolution. We ran two simulations for the period 2001-2018, with the only difference being the inclusion or exclusion of landfast ice information based on observations. All other factors, including initial conditions, resolution, and atmospheric forcings, were kept the same. We then compared the results of these simulations with observations from the Advanced Microwave Scanning Radiometer (AMSR) to evaluate the performance of the new simulation. Our analysis allowed us to determine the extent to which prescribing the distribution of landfast ice and setting the sea ice velocity to zero on landfast ice regions influenced various aspects of the sea ice, such as polynyas, landfast ice, and sea ice distribution in the model. In the future, we plan to refine this technique by using higher resolution (1/4 degree) and testing more complex methods, such as assimilating icebergs and physical parameterization.