Prospecting for Hydrothermal Vents Using Moored Current and Temperature Data: Axial Volcano on the Juan de Fuca Ridge, Northeast Pacific

Abstract

Tidal and inertial currents and profuse hydrothermal discharge at recently erupted Axial Volcano, Juan de Fuca Ridge, cause relatively large and rapid temperature (T) changes in the near-bottom water column. Measurements show short-term T variations of as much as 0.13°C at 30 m and 0.18°C at 150 m above bottom and currents that have strong tidal components and means of 3?5 cm s?1. Locations and magnitudes of the hydrothermal sources leading to the observed T variations have been inferred via an inverse calculation. Results imply noncongruent source regions around the mooring site for plumes from low- and high-buoyancy flux sources. Water column and seafloor observations in the volcano?s caldera region generally support the distribution of source types and sites inferred. A high-buoyancy flux, ephemeral venting site, unexpected on the eastern shoulder of the volcano, is also indicated by the inverse calculation and supported by water-column survey data. Over the O(10 km2) calculation region, heat flux from low-buoyancy hydrothermal sources is apparently less than heat flux from high-buoyancy hydrothermal sources, a result that is in disagreement with previous reports on the balance of heat flux between vent source types.