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Abstract:
Polynyas, the regions of open water or thin sea-ice surrounded by thicker sea-ice, are sources of Antarctic Bottom Water (AABW), due to the strong buoyance loss and sea-ice production here. Accurate estimation of sea-ice production (SIP) is crucial to understanding the AABW formation. Polynyas can be classified into sensible-heat and latent-heat polynyas resulting from their formation and sustainable mechanism. With an unrealistic assumption of zero sub-ice oceanic heat flux, previous estimations of SIP based on the heat-budget method are mainly limited to latent-heat polynyas. In this study, based on the sea-ice volume-conservation (VC) theory, we developed a new method that can consider cases with sea-ice melting (negative SIP). Moreover, using this method, we estimate the ice–ocean heat flux via satellite observations combined with atmospheric reanalysis data indirectly for the first time. For a latent-heat polynya—the Ross Sea Polynya—this method captures the synoptic SIP variations affected by warm modified Circumpolar Deep Water (mCDW) intrusions, including small-scale melting and freezing patterns. For a sensible-heat polynya—the Maud Rise Polynya—we confirm that there is a sea-ice melting induced by warm water uplifted by Ekman pumping with a rate of 0.15 and 1.44 cm d-1 for 2016 and 2017, respectively.
