Nature 227, 1041 - 1043 (05 September 1970); doi:10.1038/2271041b0

Temperature Gradient above the Deep-Sea Floor

MARK WIMBUSH

Institute of Geophysics arid Planetary Physics, La Jolla Laboratories, University of California, San Diego.

AT sufficient ocean depths (several km) there is an increase of temperature with depth corresponding to the adiabatic lapse rate 10^-6 °C/cm. Toward the bottom, the gradient becomes increasingly superadiabatic, because the water is heated from below by a geothermal heat flux H. Because H is small (10^-6 calories cm^-2 s^-1), only a slight superadiabatic effect is expected: |dT/dz| < 2 at elevation z > 1 m. Measurements of hyperadiabatic gradients (|dT/dz| = 10−1,000 ) several metres, or even tens of metres, above the bottom have been reported¹⁻⁴, though it seems inconceivable that a strongly unstable layer several metres thick can persist. The experiment described here indicates that |dT/dz| = 1.3 at z 1 m.

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