Thermal gradient measurements in the water and bottom sediment of the western Atlantic

A new instrument for obtaining thermal gradient measurements in ocean bottom sediments, called a thermograd, is described. The thermograd is attached to a piston coring device, and it measures temperatures simultaneously at three or more depths in the sediment while obtaining a core for later thermal conductivity measurement. Thermistor needle probes are used to achieve thermal equilibrium with the sediment in about 1 minute after penetration. In situ calibration of the sensors is achieved at each station by recording temperature in the deep ocean waters. Fourteen thermal gradient measurements were obtained in the sediments of the western Atlantic Ocean with an average probe penetration of 10 meters. The average computed heat flow for 11 basin measurements is 1.42 μcal/cm2 sec. A measurement in the mid-Atlantic ridge indicates heat flow of 3.37 μcal/cm2 sec, and one in the Puerto Rico trench is 1.17 μcal/cm2 sec. Nearly continuous water temperature measurements are shown for 15 stations extending from about 2000 meters deep to the ocean bottom. This article contains supplementary material.