Variability in the bottom water of the Weddell Sea

Abstract

The variability of bottom water outflow is examined by reference to hydrographic sections repeated on successive years in the northern Weddell Sea and also by examination of a 349-day record obtained from a current meter mounted 50 m off the bottom near the southern end of the sections. The repeated sections indicate that bottom water, outflowing in the region of the base of the Scotia Ridge in 1976, was colder, more saline, higher in oxygen, and lower in silicate than that in 1975. The time series of current velocity and temperature are characterized by a greater variability of velocity and temperature in summer than in winter. During summer the bottom water is also characterized by lower temperatures, possibly related to the intermittent nature of the formation and flow of bottom water. For both summer and winter seasons kinetic energy exists at periods consistent with planetary wave modes of the Weddell basin, however, the summer fluctuations suggest cyclonic cold-core mesoscale eddies having radii approximately equal to the Rossby radius of deformation.