Oceanographic Controls on Diffuse Flow Temperature Variability at Main Endeavour Field

Abstract:

Temperature observations from the Main Endeavour vent Field (MEF) on the Endeavour segment of the Juan de Fuca Ridge reveal large spatial variability over centimeter length scales. Five thermistor chains with ten sensors each are draped over a faunal assemblage on the the north side of the Grotto mound in the northern part of MEF. Spacing is on the order of 10 cm and the areal coverage is about a square meter. Shimmering fluids are evident in the ROV video during the deployment and recovery of the thermistors indicating that the area is a diffuse venting zone.

The temperature variability can be a result of heterogeneity in the degree of diffuse venting and/or variability in the degree of mixing with the cool ambient waters. Concurrent observations from the NEPTUNE cabled observatory are: temperature from a nearby hot fluid (330 deg) vent orifice that is weakly modulated by the surface tide (pressure), temperature from a diffuse flow area artificially sheltered from the ambient currents and measurements of currents from a bottom-mounted ADCP. We use these measurements to argue that the temperature variability is the result of interaction of the buoyant flow with the oceanic currents in the boundary layer at the level of the faunal assemblage.