A Volume-Conserved Approach to Estimating Sea-Ice Production in Antarctic Polynyas

Accurate estimation of sea-ice production (SIP) is crucial to understanding the formation of Antarctic Bottom Water (AABW). Existing SIP estimates depend on the heat-budget method, using atmospheric reanalysis together with satellite-derived sea-ice thickness data, and make an unrealistic assumption of no ocean heat flux occurring below the ice. Here, we propose a new method to estimate SIP based on the sea-ice volume-conservation (VC) theory. This new method can consider cases with sea-ice melting (negative SIP). For a latent-heat polynya-the Ross Sea Polynya-this method captures the synoptic SIP variations affected by warm-water intrusions, including small-scale melting and freezing patterns. Using the new VC approach for a sensible-heat polynya, the Maud Rise Polynya, the sub-sea-ice oceanic heat flux was indirectly estimated, and the sea-ice melting rate induced by warm water uplifted by Ekman pumping was estimated to be 0.15 and 1.44 cm d(-1) for 2016 and 2017, respectively.

Automated summary

Accurate estimation of sea-ice production is crucial for understanding Antarctic Bottom Water formation. Existing methods have unrealistic assumptions and cannot consider sea-ice melting. We propose a new volume-conservation based method that captures synoptic SIP variations, including small-scale melting and freezing patterns. Using this method, we estimated the sea-ice melting rate induced by warm water in the Maud Rise Polynya to be 0.15 and 1.44 cm d(-1) for 2016 and 2017.