Variability of currents in Great South Channel and over Georges Bank : observation and modeling

Abstract

This thesis consists of two parts: (I) variability of currents and water properties in late spring in the northern Great South Channel and (II) numerical study of stratified tidal rectification over Georges Bank. In part I, the combined analysis of CTD, ADCP, satellite-track drifters, and zooplankton distributions in the northern Great South Channel clearly shows (1) the seasonal evolution of the surface low salinity plume, (2) the threedimensional structure of residual flow, and (3) a coherent relationship between the surface low salinity plume and high concentration of zooplankton. In part II, the numerical model of Georges Bank shows that as the fluid becomes stratified , tidal mixing and rectification intensify both along- and cross-bank residual currents and modify the vertical structure of the flow. Along- and cross-bank residual currents increase as either stratification increases or the depth of the bank decreases. Model results over Georges Bank are in good agreement with observation, particularly in the position of the tidal mixing front and residual currents on the northern flank of the Bank.