Flow Mow Electronic Cruise Report

Heat flux measurements at the Main Endeavour Vent Field, Juan de Fuca Ridge

Fritz Stahr, Russell McDuff, University of Washington
Dana Yoerger, Alan Bradley, Woods Hole Oceanographic Institution
Ko-ichi Nakamura, Geological Society of Japan

An essential element of oceanic hydrothermal systems is heat transfer out of the crust by the convection of seawater. Previous investigations of heat flux have concentrated on the Endeavour Segment of the Juan de Fuca Ridge, primarily at the Main Endeavour Vent Field (MEF). While the reported values are of a reasonable magnitude, they vary widely, are uncertain by as much as a factor of five, and cover incomparable ranges of space, time and styles of venting (focussed and diffuse). The Flow Mow project, conducted in August 2000, provides a new and fundamentally better measurement of heat flux from the MEF. The data were collected primarily using the Autonomous Benthic Explorer (ABE) from WHOI, as well as a precisely navigated CTD. Instruments on ABE included a Sea Bird pumped and ducted CTD, a MAVS current meter, and a redox potential (Eh) measuring instrument. Navigation of ABE within a long-baseline network of transponders and pressure-derived depth allows correction of velocity for vehicle motion. The approach taken relies on ABE's ability to survey the vent field quickly and completely. ABE dives enclosed all sides of a 700 m by 300 m by 75 meter-above-bottom box over the field, concentrating on many repeat passes over the top where the primary heat flux is. The dives ranged from approximately 8 to 30 hours, covering several full tidal cycles and including up to 5 repeat occupations of the top on one dive. The 75 mab height was chosen to best balance the magnitude of buoyant plume signals while repeatably intersecting all plumes within the field regardless of origin or venting type. ABE surveyed the sides of the box down to within 5 m of the bottom several times to capture plumes being advected laterally from the box by tidally driven currents. We report the initial results of our analysis of the data, as well as a brief description of the instrument and vehicle operation.

MORP Home | Flow Mow Home | Search Flow Mow Pages (not yet implemented)

Flow Mow Web
Maintained by the Flow Mow Group (flowmow@ocean.washington.edu)
Copyright (©) 2000 University of Washington; Copyright Notice
Content Last Modified 9/25/2000
Page Last Built 9/25/2000