Abstract:
Estimates of the heat output of hydrothermal vents, identified
along the Endeavor and Southern Segments of the Juan de Fuca Ridge,
are used to evaluate the total heat flux associated with
hydrothermal circulation for the ridge segment. An array carried by
D/V ALVIN sampled the temperature and velocity structure of
hydrothermal plumes from individual vents . The maximum heat flux
calculated for a single vent is 50 MW, but the average vent output is
only 13 MW per vent for 31 vents. The estimates for any given vent
may vary over an order of magnitude. This uncertainty is due mainly
to the difficulty of locating the centerline of the plume relative to
the point of measurement, although the uncertainty in determining
the constants from the appropriate equations based on laboratory
experiments contributes a significant share to the net error. For the
Endeavor Segment, the minimum total geothermal heat flux due to
hydrothermal circulation exceeds 70 MW. The minimum estimate for
the Southern Segment is 16 MW. The maximum estimate is probably
closer to the total heat flux (236 MW and 66 MW respectively) . The
estimated heat flux density is 3300 W/m2 for the Endeavor vent
field and 39 W/m2 for the Southern vent field. Focused hydrothermal
venting accounts for only a small fraction of the heat available
according to steady-state predictions of conductive heat flux;
however, other hydrothermal phenomena (e.g., diffuse flow) account
for the greater share of the total hydrothermal heat flux.
