CTDT Characterization of Ridge Crest Hydrothermal Activity

A preview of a poster submitted for presentation at the 1996 Fall meeting of the American Geophysical Union by Scott Veirs.

This plot supplements the text of my abstract because it shows how closely spaced are the measurements conductivity, temperature, depth, and transmissivity (CTDT), compared to past hydrographic surveys of hydrothermal activity over spreading center axes. The maroon transects were conducted at the beginning of the summer of 1995, while those in blue were completed at the end of that summer. Click on the map if you'd like to peruse a slightly higher-resolution version of the graphic.

Abstract Text:

Accurate characterization of hydrothermal activity above submarine spreading centers offers insight into both subsurface circulation, and heat and biogeochemical fluxes between ridge crest and other Earth systems. Unfortunately, efforts to map the distribution and evolution of 3 dimensional hydrothermal plumes with 2 dimensional "tow-yo" transects can be frustrated both by variability from currents, and water column measurements too sparse to describe a dynamic hydrographic field.

In an intensified effort to survey hydrothermal activity with attention to bottom current variability, 56 CTDT (conductivity-temperature-depth-transmissivity) transects were completed along and across 12 km of the Endeavour Segment axial valley on the Juan de Fuca Ridge. The CTDT data are unprecedented in their spatial density, the frequency with which stations are re-occupied, their proximity to a dual (25 and 300 meters off bottom) current meter mooring, and their geographic reference within the RIDGE Observatory using long baseline navigation.

The 1995-1996 data reveal the spatial correlation of hydrographic features with mapped geologic structures. Not only are plumes from 2 known vent fields recognizable, but 2 new vent fields were located by their unique CTDT character. The unusually high areal density of measurements made 10 to 50 meters above the sea floor enables generation of the first plan-view map of near-bottom hydrothermal phenomena, likely representing the spatial relationship between focussed and diffuse flow.

Work in progress combines the CTDT and current meter data to model plume advection, locate distinct hydrothermal sources, and estimate heat and particle fluxes from vent fields and the entire Segment.