A modeling study of the North Atlantic Current

• Main Author: Rowley, Clark David
• Format: Text
• Language: English
• Published: DigitalCommons@URI 1997
• Subjects: Oceanography; Curl; Separation Point; Newfoundland; north atlantic current; North Atlantic
• Online Access: https://digitalcommons.uri.edu/dissertations/AAI9723572

A model of the Newfoundland Basin is configured using the Princeton Ocean Model and a regional historical hydrographic climatology. The model resolution is 1/8$\sp\circ$ in latitude and longitude, with 11 sigma levels in the vertical. The model forcing includes applied transports along the open boundaries, a climatological wind-stress at the surface, and heat and salt fluxes at the surface calculated using a linear damping with a time constant of 180 days. The vertical eddy viscosity and diffusivity depend on the local Richardson number. The model reproduces the major observed features of the regional circulation: the mean path of the North Atlantic Current east of the Grand Banks, the pattern of stationary meanders, the pattern of high eddy energy levels, the offshore high pressure cells, and the multiple fronts near 50$\sp\circ$ to 53$\sp\circ$N. The meanders do not propagate upstream or downstream in the manner of Gulf Stream meanders. The Newfoundland Seamounts are responsible for the 44$\sp\circ$N meander trough. Three experiment sets are run with a three-layer eddy-resolving quasigeostrophic model in a square flat-bottom basin with slip sidewalls, forced with a wind-stress curl and imposed volume transports at the boundary, and by Laplacian friction and bottom drag. The model grid spacing is stretched in the zonal direction and regular in the meridional. (I) A meridional overturing cell simulated through transports applied in the surface and bottom layers shifts the separation point poleward by O(300) km with each 2 Sv increase in the meridional transport. (II) A zonal wind-stress curl pattern is imposed that simulates the local minimum near 40$\sp\circ$N in the zonally-integrated Sverdrup transport in the North Atlantic. The local minimum forms a subtropical recirculation south of the primary jet, which is isolated from the main subtropical gyre by an eastward jet near the latitude of the transport minimum. (III) A feedback mechanism is imposed that determines the surface curl forcing based on the position of the surface layer jet. This reproduces the tilt to the wind-stress curl in the North Atlantic.