Sea Ice Production in the 2016 and 2017 Maud Rise Polynyas

Sea ice production within polynyas, an outcome of the atmosphere‐ice‐ocean interaction, is a major source of dense water and hence key to the global overturning circulation, but is poorly quantified over open‐ocean polynyas. Using the two recent extensive open‐ocean polynyas within the wider Maud Rise region of the Weddell Sea in 2016 and 2017, we here explore the sea ice energy budget and estimate their sea ice production based on satellite retrievals, in‐situ hydrographic observations and the Japanese 55‐year Reanalysis. We find that the oceanic heat flux amounts to 36.1 and 30.7 W m−2 within the 2016 and 2017 polynyas, respectively. Especially the 2017 open‐ocean polynya produced nearly 200 km3 of new sea ice, which is comparable to the production in the largest Antarctic coastal polynyas. Finally, we determine that ice production is highly correlated with and sensitive to skin temperature and wind speed, which affect the turbulent fluxes. It is also strongly sensitive to uncertainties in the sea ice concentration and 1,000 hPa temperature, which all urgently need to be better monitored at high latitudes. Lastly, more process‐oriented campaigns are required to further elucidate the role of open‐ocean polynya on the local and global ocean circulations. Plain Language Summary Polynyas, openings in the sea ice, are crucial places for sea ice formation and often referred to as “ice factories.” However, this ice production, which is critical to the formation of very dense and cold Antarctic Bottom Water (AABW), is rarely quantified for open‐ocean polynyas. Here, we determine the sea ice volume produced within the latest 2016 and 2017 Maud Rise polynyas based on various satellite‐retrieved observations by computing the heat budget throughout the ice. We also estimate the upper oceanic heat fluxes before and during a polynya from in‐situ measurements within the polynya. This oceanic heat flux is crucial, as it strongly impacts ice formation. We estimate that the 2017 polynya produced an amount of ice comparable to that in the largest coastal polynyas. Finally, we find linkages between air temperature, wind speed, ocean current and our estimated sea ice formation and show that the estimation accuracy largely depends on the near‐surface atmospheric and sea ice conditions. The sea ice production estimated in this study can be used to better assess the air‐ice‐ocean interactions in the rapidly changing polar regions, but still, more work is needed to clarify its i