Article,
Deep-ocean temperature variations and implications for errors in seafloor heat flow determinations
Journal of Geophysical Research-Solid Earth, 108 (B1): 2034 (2003)
Abstract
1 The accuracy with which seafloor heat flow is determined depends
on the temporal stability of bottom water temperature. Indirect tests
for stability are provided most commonly by observing the uniformity
of heat flow with depth. This criterion is met to a high degree of
certainty at two sites in the eastern North Pacific Ocean, where
colocated high-quality probe and borehole heat flow data can be compared.
A more direct test for stability is provided by long-term observations
of bottom water temperature. Previously published records and new
data show temperature variations of only a few hundredths of a degree
at sites in the central and eastern North Atlantic and the eastern
North Pacific. Resultant gradient perturbations are geothermally
insignificant (<5 mK m(-1)) at depths greater than 1-2 m below the
seafloor, consistent with the uniformity of heat flow with depth
observed in these areas. Geothermally problematic bottom water temperature
variations are observed or inferred in the western North and South
Atlantic and western South Pacific. Variations range up to &PLUSMN;0.15
K and are capable of producing gradient perturbations of up to 5
mK m(-1) at depths as great as 5 m below the seafloor. While these
data are instructive, their distribution is not adequate to provide
general guidelines for estimating geothermal gradient perturbations.
Data from shallower sites are needed in all oceans to define depth
limits of acceptable bottom water temperature variability, and from
other deep-ocean locations where near-source bottom water transients
or vigorous deep-water circulation dynamics are likely to be present.
