The Impacts of an Explosive Cyclone on the Upper Ocean and Sea Ice Over the Southern Ocean Based on Numerical Modeling Results

Abstract

Explosive cyclones are intense extratropical synoptic systems associated with severe weather in the mid-to-high latitudes, particularly over the Southern Ocean. This study employs a recently developed ROMS-CICE coupled model, incorporating a cyclone-removal method, to simulate and quantify the response of the upper ocean and sea ice to an explosive cyclone traversing the Southern Pacific Ocean. The modeling results indicate that the maximum instantaneous sea surface warming anomaly reaches up to 0.20°C around the center of the explosive cyclone, while a cooling anomaly of about −0.15°C is observed at the cyclone's periphery. Beneath this surface anomaly, a cooling of up to −0.15°C occurs in the area-averaged subsurface ocean layer at depths of 20–60 m. Concurrently, the sea surface salinity experiences an increasing anomaly of up to 0.20 practical salinity units (psu), accompanied by a decrease in salinity within the subsurface ocean layer at depths of 30–60 m. These anomalies gradually weaken over the subsequent 28–30 days but sustain minor anomalies for more than 1 month, particularly in the subsurface ocean layer. Further analysis of the temperature and salinity tendency equations reveals that advection and vertical diffusion primarily contribute to both the surface and subsurface responses, with vertical diffusion serving as the main driver behind the observed uniform patterns. Additionally, sea ice concentration and thickness demonstrate reductions of more than 25% and 0.2 m near the coast, respectively, resulting from dynamic forcing and the contributions of basal ice melting due to the transport of warmer water currents beneath.