C-3 Precise Measurement of the Heat Flux from a Hydrothermal Vent System

The very essence of a hydrothermal system is transfer of heat by a convecting fluid. Despite this central role played by heat transfer, we have a woefully poor knowledge of the flux of heat from seafloor hydrothermal systems and its variation through time. This lack of knowledge is not from a lack of trying. Many different investigators have made estimates of the flux of heat from seafloor hydrothermal systems. The Endeavour Segment of the Juan de Fuca Ridge is perhaps the beststudied example [Baker and Massoth, 1987; Rosenberg et al ., 1988; Thomson et al ., 1992; Schultz et al . , 1992; Bemis et al. , 1993; Ginster et al . , 1994]. We will return to the details of these studies, but for now there are issues of what style(s) of venting are included in the estimates, the errors inherent in the measurements, sampling statistics, and the spatial and temporal averaging that is associated with each of the individual approaches. Thus, while the reported values are of a reasonable order of magnitude, the resulting estimates vary widely (from ~100 to ~10000 MW), have large uncertainties (often spanning an order of magnitude), and do not allow us to address very fundamental questions, for example, is the flux of heat steady or varying through time? We propose to take advantage of technological advances in deep sea autonomous vehicles to make precise measurements, achieving uncertainty better than 20%, of the heat flux from the Main Endeavour Field (MEF) [ Delaney et al. , 1992], and as t ime permits a series of nearby vent fields.