Mesoscale variability and mean flow interaction near the Gulf Stream as seen by satellite altimetry and numerical modelling

Abstract

The interaction between the eddy field and the mean flow near the Gulf Stream is studied here using satellite altimeter measurements and an eddy resolving numerical model. The eddy vorticity flux in the quasigeostrophic framework is obtained from the stream function standard deviation and spatial correlation function assuming the correlation function is homogeneous. An analytical expression is found for the stream function correlation using the altimetric and numerical data. Cases when the correlation function is anisotropic are compared to the isotropic case previously studied by Hogg (1993), who found that the eddy vorticity flux drives two counter rotating gyres on either side of the stream. The anisotropy can be important in the eddy vorticity flux, even when its departure from the isotropic case is small. Meridional or zonal anisotropies can drive recirculation gyres similar in strength and position to the ones driven by the isotropic case. The results when including anisotropy in the diagonal direction suggest that the homogenoeus assumption may not be valid.