Dynamical Adjustment of the Gulf Stream


This NSF-supported project is an experimental study of Lagrangian potential vorticity (PV) in the Gulf Stream for two distinct cases: One, for particles in the center of the Stream, to evaluate quantatively the hypothesis of a `frozen' velocity to estimate the mutual adjustments between curvature, shear and stretching vorticity; two, for particles that are entrained and expelled at the northern edge of the Stream, to study quantitivatively how particles conserve PV, if they do, as they transit between the quiet Slope Water and dynamic Gulf Stream.

This project is being conducted by Tom Rossby , Dave Hebert and graduate student Jayendran Rajamony


One of the objectives of this study is to address the potential vorticity adjustment of fluid parcels in the process of extrainment or expulsion at the northern edge of the Gulf Stream, either at troughs or crests of meanders. The time scales (1-3 days) and lateral scales (10-20 km) of the cross-frontal motion are such that isopycnal Swallow floats modified to measure stratification are particularly advantageous. Together with a CTD and acoustic Doppler current profiler (ADCP), one can estimate all of the terms of the full (Ertel) potential vorticity (PV) of a water parcel.

To examine the dynamics of the cross-frontal exchange between the Gulf Stream and the Slope Water, two cruises were undertaken. The first cruise studied the adjustment of the potential vorticity at the end of winter (Apr.-May 1995), when the contrast in the structure of the upper ocean between the two water masses is a maximum. The second cruise was at the end of summer (Aug.-Sept. 1995) when the contrast is minimal. A brief description of the cruise can be found here.

As part of this study, we have examined whether a shipboard acoustic Doppler current profiler (ADCP) can used in realtime to track a water parcel. Some results of this study was presented at the 1996 Ocean Sciences meeting in San Diego by Jayendran Rajamony.


We thank Jim Fontaine for the construction of the isopycnal Swallow floats >, Sandy Fontana for her assistance, especially with the shipboard ADCPs, Jan Szelag for his help with the CTDs and the captains, crew, watch keepers and marine techs (too numerous to name) for their assistance during the OCEANUS and ENDEAVOR cruises. This project was supported by the National Science Foundation Grant OCE-9314480.

Last Revised: 26 March 1996