Investigating Iceberg–Sea Ice Interactions in the Southern Ocean Using NEMO-ICB

Icebergs, formed by the calving of the Antarctic ice sheet, are among the most emblematic natural features of the polar regions. Their presence in the Southern Ocean, an essential carbon and heat sink, raises important questions about their role in the future evolution of the ocean and climate. As the mass balance of the Antarctic ice sheet continues to decline, it is crucial to better understand how iceberg-sea ice interactions influence ocean dynamics and sea ice variability in the Southern Ocean.   

 In this study, we use the NEMO version 4.2.2 ocean model coupled to the ICB module (Iceberg) to investigate these interactions. Our approach has two main objectives:  (1) We assess the impact of icebergs on the ocean and sea ice by running two 30-year regional hindcast simulations of the Southern Ocean, one with the ICB module enabled and the other with the module disabled. This allows us to isolate the influence of iceberg dynamics on sea ice concentration and thickness, along with ocean physical properties such as surface temperature and salinity.  And (2) by implementing a sea ice locking process in the ICB module we aim to better represent the mechanical interactions between icebergs and sea ice, particularly when icebergs become 'trapped' by thick, highly concentrated sea ice. Sea ice locking has a major impact on the distribution of freshwater fluxes in the ocean, by influencing the trajectory of icebergs.  

This study is a first step towards improving our understanding of the coupled iceberg-sea ice-ocean system and its implications for the future evolution of the Southern Ocean in a changing climate.