Laboratory Simulation of Western Boundary Currents Over Shelf Topography and of Their Extensions

Project acronym:	HyIII-NTNU-15
Name of Group Leader:	Prof. Stefano Pierini, University of Naples Parth
User-Project Title:	Laboratory Simulation of Western Boundary Currents Over Shelf Topography and of Their Extensions
Facility:	Coriolis platform
Proceedings TA Project:	Laboratory simulation of western boundary currents over shelf topography and of their extensions
Data Management Report:	Report

User-Project Objectives

Summary:

The aim of this experimental study was to extend substantially a previous laboratory campaign carried out in the same laboratory in 2003, concerning the modeling of strongly nonlinear western boundary currents (Pierini et al., J. Phys. Oceanogr., 38, 1073-1090 ). This time we have analyzed very relevant flows that could not be studied previously (and that have required changes in the setup), such as: (1) western boundary currents in the weakly nonlinear limit, (2) western boundary currents over shelf topography and (3) western boundary current detachment from the coast due to coastal interactions.

A preliminary analysis of the obtained results indicates that all the scientific aims have been achieved. The transition from highly nonlinear western boundary currents to weakly nonlinear ones is now evidenced in the measurements, so that an unprecedented coverage on the range of nonlinearity for WBCs is now available in terms of experimental data. The simulation of the effect of sloping sidewalls has been properly carried out, and those data will be analyzed in detail on the basis of theoretical arguments.

Perhaps the most interesting results concern the third part of the study. While for weak WBCs the current follows the coast even past the cape, for strong WBCs a free jet is found to detach from the coast. Thus, it was clearly shown that WBC detachment can be produced by a discontinuity of the coastline. Moreover, the transition between these two very different behaviors is marked by a case corresponding to the experiment of Pierini et al. (2008) that was found to be virtually dynamically similar to the Gulf Stream. Thus, insofar as this simple analysis represents a rough representation of the North Atlantic WBC, this result would seem to suggest that a sufficient weakening of the Gulf Stream intensity would prevent flow separation past Cape Hatteras. Naturally, a real oceanic WBC is far more complex than such a simple mechanistic dynamical model, but nonetheless, these results can constitute the basis for more realistic and significant laboratory experiments that could be performed in the future.

Back