Variability of thermal structure off Georgia,winter 1978

Temperatures recorded over the Georgia shelf and at near-bottom locations on the slope are compared with records of thermocline elevation from inverted echo sounders on the slope and with shore wind observations, for the period January to April 1978.Both upwelling and downwelling events are observed. Upwelling events are associated with upwelling-favorable wind and/or Gulf stream frontal eddies. Strong upwellings are accompanied by risings of the thermocline over the slope, but some weaker eddies occur without noticeable thermocline disturbance. Downwelling events are associated with onshore meander crests of the Gulf Stream, and sometimes with downwelling-favorable wind. The influence of downwelling does not extend seaward of the upper slope.A long-term (1 month) variation of the thermal structure is observed at the shelf break and under the Gulf Stream. It is related to a filament of cold water on the slope, varying in path and size. This cold filament appears to be Antarctic Intermediate Water which is variably advected through the Straits of Florida. Theory suggest that the variability may be caused by changes in the thermocline depth and tilt across the Gulf Stream in response to transport fluctuations.