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Abstract:
The Southern Ocean is considered as the home to explosive cyclones (ECs) that are associated with severe weather in the mid-to-high latitudes. We investigate the climatology and trend of ECs over the Southern Ocean during 1980-2020 by combining a method that is most suited for identifying and tracking cyclones in the Southern Ocean and a latest climate reanalysis. On average, there is about 50 explosive cyclones generated annually over the Southern Ocean, with a significant increasing trend of 2.3 per decade during 1980-2020. This trend is dominated by the positive trend of strong ECs, especially in autumn. Some studies have examined changes of atmosphere, ocean, and sea ice associated with ECs on some case studies. Here we present the composite effects of multiple ECs over a key region having the largest climatological and increasing trend of track density on anomalies in atmospheric circulation, surface energy budget, sea surface temperature, and sea ice cover and their persistence. To further determine the effects of ECs, we use a recently developed ROMS-CICE coupled model to quantify how the upper ocean and sea ice respond to a selected EC. The results show the responses of the upper ocean and sea ice, which can sustain for a couple of weeks. Further analysis of the mixed layer heat budget equation suggests that sensible and latent heat fluxes and entrainment are major contributors to sea surface temperature anomalies caused by EC, and dynamic process is the major factor to produce sea ice anomalies.
