The Oleander Project: Sustained Observation of Ocean Currents and Transports in the Gulf Stream and Adjacent Waters from New York to Bermuda

University Of Rhode Island, Kingston RI

Investigators

Abstract

0241654 Rossby Ten years ago a program was initiated to directly measure upper-ocean currents from the U.S. continental shelf to Bermuda from a container vessel, the CMV Oleander, with special focus on long-term variations in the strength of the Gulf Stream. The high horizontal resolution repeat sampling of the Gulf Stream and adjacent gyres, made possible by the weekly shipping to Bermuda, has led to estimates of upper-ocean transports and their variability with an absolute accuracy previously unachievable. While any single estimate of upper-ocean transport will have an inherent uncertainty in the 15-20% range, repeat sampling can reduce this to just a few percent at most. For the 1993-2001 Oleander observing period, the largest observed inter-annual variations in Gulf Stream transport had a magnitude of +/-8%, peak-to-peak, when estimated annually. Since these variations appear to occur on time scales characteristic of the North Atlantic Oscillation, it is not yet clear whether these are typical, small, or large numbers. Nor can one at present distinguish between different hypotheses regarding forcing mechanisms. This project will continue the Oleander sampling program for another five years. Proposed enhancements include the installation of a new state-of-the art acoustic Doppler current profiler and optical compass. These will improve consistent sampling of the velocity field to significantly greater depths. EXpendable BathyThermograph (XBT) casts along the Oleander track will continue to be taken monthly by the National Marine Fisheries Service. Scientific objectives include the investigation of linkages between four oceanographic regimes (outer continental shelf, Slope Sea, Gulf Stream, and Sargasso Sea) and their connections to large-scale forcing fields. In particular, observations obtained to date suggest a stronger thermohaline role to the variability of the Northwest Atlantic than perhaps previously recognized. These are complex issues and the Oleander data set will be far more effective when used in conjunction with other studies and modeling efforts. To facilitate such synergies, the Oleander's data will be acquired each time she enters port, and the processed data posted in near real-time on a web-based server. With a growing focus on real-time ocean forecasting, these observations and related products can play an increasingly useful role in forecast validation and model improvements. Other research activities can avail themselves of these data, and may find it advantageous to design field programs around this data availability. It is also proposed to prepare observations for use by a wider public, particularly the sailing community. The Graduate School of Oceanography at the University of Rhode Island has an active web-based program for the K-12 community and collaborations in this area will be explored.