North Atlantic Current Project


The North Atlantic Current is being studied by a group of observationalists and modellers here at URI/GSO, with Dr. Tom Rossbyand Dr. Lew Rothstein as co-principal investigators. Among the observational studies are a multi-year RAFOS float study and a regional climatology of the Newfoundland Basin on neutral surfaces.


RAFOS Float Studies


The objective of the RAFOS float program, jointly supported by the Office of Naval Research and the National Science Foundation, was to study the structure of the currents in the North Atlantic Currrent (NAC) region and the exchange of waters between the subtropical and subpolar gyres in the Newfoundland Basin. One hundred RAFOS floats were deployed on two density surfaces corresponding to sigma-theta = 27.2 and 27.5, respectively. All floats were designed to cycle once or twice a day to density surfaces 0.1 sigma-t units above and below their nominal level to determine changes in stratification and temperature along the trajectories. Three separate float deployments took place: July-August 1993, November-December 1993 and October-November 1994. Most float missions had a duration of ten months, with the final floats surfacing in the summer of 1995. At the end of its mission, each float releases its ballast weight, returns to the surface, and telemeters data to Argos, a French satellite-based data collection and platform location system. Once all the data are downloaded and processed, the trajectory of the float can be reconstructed from the time series of acoustic travel times. The pressure and temperature time series are also included in the telemetered data. The floats were tracked using four moored sound sources developed by Sparton of Canada, energized by power modules from Webb Research Corp. of East Falmouth, Massachusetts.

We present here a movie of the float trajectories. Your browser must be java 1.0 ready (Netscape 3 or greater). Also presented are summary plots of the float trajectories on each density surface. For additional information or a copy of our data report, please contact Dr. Tom Rossby or Ms. Sandra Anderson-Fontana at the Graduate School of Oceanography.

Java-based movie of Float Trajectories

Spaghetti Plots of Float Trajectories:


References

Anderson-Fontana, S., M. Prater and T. Rossby. RAFOS float data report
   of the North Atlantic Current study, 1993-1995. GSO Technical Report
   No. 96-4, September 1996, 241 pp.
Carr, M. E., E. J. Kearns and T. Rossby, 1995. Isopycnal RAFOS floats as
   roving hydrographers in the North Atlantic Current region. ACCP Notes,
   II(2), NOAA Atl. Oceanogr. and Meteorol. Lab., Miami, Fla.
Rossby, T., 1996. The North Atlantic Current and surrounding waters: at
   the crossroads. Rev. Geophys., 34, 463-481.
Rossby, T., D. Dorson, and J. Fontaine, 1986. The RAFOS system. J. Atmos.
   Oceanic Technol., 3, 672-679.
Rossby, T., J. Ellis and D. C. Webb, 1993. An efficient sound source for
   wide-area RAFOS navigation. J. Atmos. Oceanic Technol., 10, 397-403.
Rossby, T., J. Fontaine and E. C. Carter, Jr., 1994. The f/h float -
   measuring stretching vorticity directly. Deep-Sea Res., 41, 975-992.

Regional Climatology


A climatological description of the North Alantic Current (NAC) region has been developed from the historical hydrographic record as provided by the National Oceanographic Data Center. The climatology is described on specific volume anomaly surfaces which provide approximations to the neutral surfaces upon which water parcels are free to move and mix laterally. The median depth, temperature, salinity, potential density, potential vorticity, and Montgomery potential (an exact stream function on specific volume anomaly surfaces) are described on a 0.5 degree grid for the Newfoundland Basin. This regional climatology presents a fine scale neutral surface view of the waters of the Newfoundland Basin which allows a more detailed study of the system than is afforded by other existing climatologies for the North Atlantic.

A complete discussion of the climatology may be found in the following (gzipped) postscipt documents:

Through the NAC climatology page, users may gain access to the median climatological fields, their errors, streamfunctions, decadal and seasonal subsamples, and more. The data are available in netCDF and ASCII format as well as GIF89a images.

Questions or problems concerning this climatology should be addressed to Dr. Edward Kearns at the University of Miami. 


Related links


Back to the RAFOS group's home page.

This page was last modified on August 24, 1999.