Eighteen Degree Water variability

Talley, LD, Raymer ME.  1982.  Eighteen Degree Water variability. Journal of Marine Research. 40:757-775.


The Eighteen Degree Water of the western North Atlantic is formed by deep convection in winter. The circulation and changing properties of Eighteen Degree Water are studied using hydrographic data from a long time series at the Panulirus station (32 degrees 10'N, 64 degrees 30'W) and from the Gulf Stream '60 experiment. Due to its relative vertical homogeneity, which persists year-round, the Eighteen Degree Water can be identified by its low potential vorticity (f/rho)(partial derivative rho/partial derivative z). The Eighteen Degree Water is formed in an east-west band of varying characteristics offshore of the Gulf Stream. The Eighteen Degree Water formed at the eastern end of the subtropical gyre recirculates westward past the Panulirus station. Renewal of Eighteen Degree Water occurred regularly from 1954 to 1971, ceased from 1972 to 1975, and began again after 1975. The properties (18 degrees C, 36.5 parts per thousand) of Eighteen Degree Water seen at the Panulirus station were nearly uniform from 1954 to 1964. There was a shift in properties in 1964 and by 1972 the Eighteen Degree Water properties were 17.1 degrees C, 36.4 parts per thousand, The new Eighteen Degree Water formed after 1975 had nearly the same characteristics as that of 1954. The density, potential temperature, salinity and the temperature-salinity relation of the entire upper water column at the Panulirus station changed at the same time as the Eighteen Degree Water properties. The upper water column was denser and colder from 1964 to 1975 than from 1954 to 1964 and after 1975.