Using a New Deep-Sea Camera System to Measure Temporal Variations of the Volume and Heat Flux of Diffuse Hydrothermal Fluids at the ASHES Vent Field

Abstract:

Estimates of the heat and volume flux of diffuse venting at mid-ocean ridge-hosted hydrothermal fields suggest that integrated diffuse fluxes can be up to 10 times the total flux due to focused, high-temperature venting. However, calculated fluxes often have uncertainties on the order of the values themselves. Previous methods to measure heat flux has generally involved either direct point measurements at the site of venting using invasive flow collectors, or indirect methods that measure fluid properties (e.g. temperature) in the effluent plume. To improve our ability to accurately measure time-series of diffuse flow, we developed a new, deep-sea camera and temperature measurement system, the Diffuse Effluent Measurement System (DEMS). The DEMS captures co-registered images and temperatures of diffuse effluent rising between a high-resolution camera and an illuminated, random dot pattern designed for calculating velocities using Diffuse Fluid Velocimetry (DFV; Mittelstaedt et al., 2010). DFV is a cross correlation technique that tracks moving index of refraction anomalies (hot parcels of fluid) through time. During the 2014 AT26-17 cruise, the DEMS was deployed with Alvin above a fracture network at the Phoenix Vent within the ASHES vent field (Axial Seamount, 1543 mbsl). The system was designed to collect 24 seconds of imagery at 20 Hz and temperatures at 1 Hz each hour over the period between July 22 and August 2^nd. To assess both diffuse and focused flow at the Phoenix Vent Site, the DEMS was deployed in conjunction with a second camera system, the VentCam, which measures the volume flux of focused vents and collected imagery at overlapping time intervals. Here, we present a basic technical description of the DEMS and the preliminary observations of diffuse heat and volume flux observed at the Phoenix Vent.