Surface and bottom boundary layer dynamics on a shallow submarine bank : southern flank of Georges Bank

Abstract

The thesis investigates the circulation at a 76-m deep study site on the southern flank of Georges Bank, a shallow submarine bank located between the deeper Gulf of Maine and the continental slope. Emphasis is placed on the vertical structure of the bottom boundary layer driven by the semidiurnal tides and the flow field's response to wind forcing.The observational analysis presented here is based on a combination of moored array and bottom tripod-mounted current, temperature, conductivity, and meteorological data taken between February and August 1995. Results from the bottom boundary layer analysis are compared to numerical model predictions for tidal flow over rough bottom topography. The flow response to wind forcing is examined and brought into context with the existing understanding of the wind-induced circulation in the Georges Bank region. Particular attention is given to the vertical distribution of the wind-driven currents, whose variation with background stratification is discussed and compared to observations from open ocean studies.

Asymmetric mixing transport: A horizontal transport mechanism for sinking plankton and sediment in tidal flows

“…The relative phases of the two components will be seen below to be unimportant. This simple model reproduces the vertical structure of the cross-bank flows in the bottom boundary layer over Georges Bank seen both in observations (Werner 1999) and in full numerical models (Fig. 5), particularly near the bottom where the assumptions that lead to a log-layer are most valid and the shear is strongest (Stull 1988).…”

“…1 and discussions of z 0 are found in basic fluid dynamics books, e.g., Kundu 1990or Stull 1988, and discussions of the determination of z 0 from data can be found in, e.g., Trowbridge and Lentz 1998. ) Typical values of z 0 are about 10 Ϫ3 m, giving a u* of about one-twentieth the horizontal currents 10 m away from the bottom (Werner 1999). Georges Bank bottom boundary layers are 10s of meters thick (Fig.…”