On the Calculation
of Total Heat, Salt and Tracer Fluxes from Ocean Hydrothermal Events
Lavelle,
J.W., E.T. Baker, and G.J. Massoth
Deep-Sea Research II, 45, 2619-2636, 1998.
Abstract:
Total heat, salt and other tracer masses released during a hydrothermal
event are shown to be proportional to, but not necessarily equal to, volume
integrals of resulting water column anomalies. Proportionality coefficients
depend on anomaly definition, on background hydrographic and tracer profiles,
on expansion coefficients of the equation of state at an appropriate pressure,
and on tracer to heat anomaly ratios at the venting source. For Gorda Ridge
event plumes, which are described in other papers o f this issue, volume
integrals of conventionally defined heat anomalies underestimate actual
released heat by a factor of 2.4 if the discharge is not anomalously saline.
Under certain combinations of hydrographic and source anomaly conditions,
not unlike those found on the East Pacific Rise at 10o N, the
apparent total heat released during and event can be deceivingly zero. This
analysis also establishes a linear relationship between the ratio of tracer
anomaly to heat anomaly at any point in the plume to the same ratio at the
source. One consequence is that the ratio of anomalous 3He to
heat in Gorda Ridge event plumes is approximately 2.4 large in the water
column that it is at the source. Results are independent of the entrainment process involved in event plume formation and they are shown to hold
true even for background hydrographic profiles that do not vary linearly
with depth.
|