The first measurements of hydrothermal heat output at 9°50′N, East Pacific Rise

Despite the importance of the heat output of seafloor hydrothermal systems for the Earthʹs energy budget, hydrothermal heat output measurements have been very limited. In this paper, we report the first measurements of hydrothermal heat output at the RIDGE 2000 Integrated Study Site on the East Pacific Rise. We focused our work on the Bio 9 complex, situated at 9°50′N, where there has been an extensive measurement and sampling program since 1991. This site is located along the eruptive fissure of the 1991/1992 event and the site of the 1995 earthquake swarm. We made direct measurements of advective heat output at several individual vents and at one site of diffuse flow (Tica). Although these data do not describe the complete heat flux picture at this vent field, the data yield a total hydrothermal heat output of ∼ 325 ± 160 MW with ∼ 42 ± 21 MW coming from high-temperature vents along this 2 km segment of ridge. This result assumes a diffuse flux similar to that measured at Tica occurs at each high-temperature vent site. Our initial measurements thus suggest that the heat output of the low-temperature diffuse venting is approximately 10 times that of the high-temperature vents, but may also be one or two orders of magnitude greater.