EVOLUTION OF THE DYNAMICAL PROCESSES OF THERMOHALINE INTRUSION IN THE SUBARCTIC FRONT OF THE NORTHWEST PACIFIC OCEAN
High-resolution observations of the upper layers of the subarctic front(SAF)in the Kuroshio-Oyashio confluence region reveal microscale thermohaline intrusion structure.There exists thermohaline intrusion water on the Oyashio side of the subarctic front with a vertical scale of 70 m(20～90 m),a horizontal width of about 6 km,and a consistent density with that of the surrounding water.The meridional flow of the intruding water moves from north to south,from the Oyashio side.Based on SAF observations,a numerical simulation of the thermohaline front was performed and the results reveal its capabilities in producing a thermohaline structure similar to our observations.This structure was essentially established by a submesoscale vortex produced by Rossby wave breaking with strong front distortion.The intrusion structure appears 20.5 days after the breaking of the frontal wave and lasts for 3 days.The evolution of kinetic parameters during the formation of thermohaline intrusion water was statistically analyzed via the Lagrangian particle tracking method.Compared with the initial field,the vertical buoyancy gradient and Ertel PV rise after the formation of the intruding water,and the horizontal buoyancy gradient is basically the same.Concerning the ageostrophic state,the corresponding Rossby number is close to O(1)order and the submesoscale processes are essentially dominated by symmetric instabilities,which play a pivotal role in the intrusion process.
thermohaline intrusionfine-scale structuresubmesoscale processesdynamic process evolution
万方数据
维普
