Influence of the gulf stream upon the short-term evolution of a warm-core ring

A large anticyclonic, Gulf Stream ring was surveyed during September 1981; two expendable bathythemographic (XBT) surveys, a conductivity-temperature-depth-oxygen (CTD-02) survey, and continuous underway measurements of velocity in the upper 100 m using an acoustic doppler velocimeter were conducted. The initial XBT survey revealed an elliptically shaped ring, over 240 km in diameter, with maximum surface velocities near 2 m s-1, situated well away from the Gulf Stream. However, the later CTD-02 and XBT surveys showed that over a 12-day period a northward meander of the Gulf Stream enveloped part of the ring. This caused a loss of water from the ring, resulting in both a decrease in ring diameter and a shoaling of the thermocline. Using the close relationship between geopotential anomaly and isotherm depths, approximately 33% of the geopotential anomaly signature of the ring is estimated to have been lost due to this event. Clearly, where such interactions with the Gulf Stream occur, they play an important role in the evolution of the warm-core rings.