Observational evidence for transformation of tropospheric waters within cyclonic rings

The North American Slope and Gulf Stream components that constitute the initial water masses within a cyclonic ring can combine with Sargasso Sea water to generate western North Atlantic water (WNAW), common to the main anticyclonic gyre in the Sargasso Sea. Evidence from the 1967 ring survey indicates that warm, saline water from above mixes with cooler, fresher water from below to produce WNAW in the region of the mid-thermocline (7-12 degrees C). At mid-thermocline depths, WNAW can be traced along sigma sub(t) surfaces from the ring center to the Sargasso Sea. Vertical stability conditions support the mixing concept. Distributions of the zooplankton species Nematoscelis megalops found for the 1975-1976 Ring D survey can be interpreted as indicating mixing and detrainment through the mid-thermocline region.