Buoyancy Flux at Ocean Weather Station Bravo

Abstract

Deep water formation at high latitudes is believed to be the driving mechanism behind the ocean's thermohaline circulation. The exchange of heat and water with the atmosphere causes the density of the surface waters to change, with subsequent downwelling and upwelling resulting as the system relaxes toward convective equilibrium. The characteristics of this atmosphere?ocean exchange are examined by studying the temporal variability of the buoyancy flux at OWS Bravo, a location where deep water formation is known to occur. The authors find that there is significant high-frequency variability in the buoyancy flux attributable to the passage of synoptic weather systems, variability that is masked by monthly analyses. At high latitudes, precipitation plays a significant role in the buoyancy flux. If it is ignored, the buoyancy loss is overestimated (positive coordinate is downward). Precipitation also causes the buoyancy flux to become positive during the passage of a cyclone. The timescale for this change in buoyancy flux is found to be similar to the timescale for the convective plumes in the ocean, suggesting a link between the two. In addition, a strong negative correlation is found to exist between the sensible heat flux at Bravo and the North Atlantic Oscillation.