The oceanic mixed layer in the Southern Ocean is characterized by numerous fronts due to the stirring of freshwater influxes arising from ice melting.The interaction of these fronts with winds modulates the evolution ...The oceanic mixed layer in the Southern Ocean is characterized by numerous fronts due to the stirring of freshwater influxes arising from ice melting.The interaction of these fronts with winds modulates the evolution of the mixed layer and affects atmosphere−ocean energy exchanges.However,the underlying mechanism behind the wind-front interaction remains obscure due to a lack of three-dimensional observations of the ocean,particularly in terms of velocities.To address this issue,this study investigates the dynamics of fronts within the mixed layer during a storm by employing a subset of the global submesoscale-permitting simulation,Northeast Weddell Sea Pre-SWOT Level-4 Hourly MITgcm LLC4320 Native Grid 2km Oceanographic Dataset(ROAM_MIZ).We first compare the ROAM_MIZ data to glider data to assess the performance of the model simulation and find that the ROAM_MIZ can,to a large degree,capture sub-mesoscale features within a mixed layer.Subsequent analyses based on a subset of ROAM_MIZ show that lateral density gradients within the mixed layer rapidly decrease during high winds associated with the storm.Down-front winds accelerate this process as the Ekman buoyancy transport responsible for enhancing the instability of the fronts is primarily dominated by horizontal baroclinic components.After the storm,the fronts strengthen again in the presence of weaker winds due to the frontogenesis by the larger-scale strain.Moreover,the non-geostrophic turbulence induces a modification of the relative vorticity,affecting the instability within the mixed layer.These findings offer valuable guidance for the deployment of observational instruments and subsequent analysis,as well as deepen the understanding of air−sea interactions in the Southern Ocean.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 42406241,42325604,42227901)the Ministry of Science and Technology of China (No. 2021YFC2803304)+2 种基金the Program of Shanghai Academic/Technology Research Leader (22XD1403600)supported by the Swedish Research Council (Nos. 2020–03190 and 2024-04209)the Swedish Research Council for the Environment, Agricultural Sciences and Spatial Planning (No. 202400375)
文摘The oceanic mixed layer in the Southern Ocean is characterized by numerous fronts due to the stirring of freshwater influxes arising from ice melting.The interaction of these fronts with winds modulates the evolution of the mixed layer and affects atmosphere−ocean energy exchanges.However,the underlying mechanism behind the wind-front interaction remains obscure due to a lack of three-dimensional observations of the ocean,particularly in terms of velocities.To address this issue,this study investigates the dynamics of fronts within the mixed layer during a storm by employing a subset of the global submesoscale-permitting simulation,Northeast Weddell Sea Pre-SWOT Level-4 Hourly MITgcm LLC4320 Native Grid 2km Oceanographic Dataset(ROAM_MIZ).We first compare the ROAM_MIZ data to glider data to assess the performance of the model simulation and find that the ROAM_MIZ can,to a large degree,capture sub-mesoscale features within a mixed layer.Subsequent analyses based on a subset of ROAM_MIZ show that lateral density gradients within the mixed layer rapidly decrease during high winds associated with the storm.Down-front winds accelerate this process as the Ekman buoyancy transport responsible for enhancing the instability of the fronts is primarily dominated by horizontal baroclinic components.After the storm,the fronts strengthen again in the presence of weaker winds due to the frontogenesis by the larger-scale strain.Moreover,the non-geostrophic turbulence induces a modification of the relative vorticity,affecting the instability within the mixed layer.These findings offer valuable guidance for the deployment of observational instruments and subsequent analysis,as well as deepen the understanding of air−sea interactions in the Southern Ocean.
