Workshop on Thermobaric Instability in High Latitude Oceans

Mcphee Research Company, Naches WA

Investigators

Abstract

This award will provide funds for the support of a workshop on thermobaric instability in the ocean, to be held at the Naval Postgraduate School in October 2000. Thermobaric instability refers to the fact that the compressibility of sea water is a non-linear function of pressure, so that a colder and fresher layer overlying a warmer and saltier layer may be statically stable, but become unstable if it is disturbed. That this effect is theoretically possible has been known for a long time, but only recently has it been considered as an effect that could actually occur in the Southern Ocean, specifically as the potential explanation of the episodic occurrence of polynyas in the Weddell Sea. The objective of the workshop is to bring together a group of oceanographers with expertise in the thermodynamics of sea water on the one hand and experience in studying the structure and characteristics of the Weddell Sea on the other hand, to explore the relevance of thermobaric instability to antarctic upper ocean dynamics, and to test it along with competing theories in explaining the observed ice and ocean phenomena of the Weddell Sea. Observations from recent oceanographic cruises, particularly those of the Antarctic Flux Study of 1997, when integrated into a simple upper ocean/ice model, have indicated that much of the eastern Weddell Sea is susceptible to thermobaric instability by the end of the austral winter. It follows that thermobaric effects may play an important role in the overall water column stability in the Weddell Sea and other regions of the Southern Ocean, may feed into the multi-year time scale of the Antarctic Circumpolar Wave, and may affect the overturning and ventilation of the high latitude ocean at even longer climatic time scales. A formal workshop on this specific aspect of antarctic oceanography has not been convened before.