OBSERVED DECAY OF A CYCLONIC GULF-STREAM RING

One mechanism by which water and energy are transferred across the Gulf Stream is by the formation of rings. Rings are formed from 300- to 400-km diameter Gulf Stream meanders which form closed current loops and separate from the main stream. This study represents the longest observation of a cyclonic Gulf Stream ring and the first such series in the western Sargasso Sea. During the observations the ring moved from off Cape Hatteras, N. C. , toward Florida with an average southwestward speed of 2 km day** minus **1. Observations consist of a variety of data: satellite infrared, expendable bathythermograph (XBT), salinity-temperature-depth recorder (STD), hydrostation, and ship drift measurements taken aboard numerous ships. The ring had a life expectancy of approximately 2. 5 years. During the final three months it moved into shallower water and the decay rate accelerated more than fourfold. Layers of Sargasso Sea water inside the ring indicated mixing with surrounding water that may be the decay mechanism of the ring. Available potential energy (APE) was shown to be useful in the study.