Heat Flow Measurements on the Reykjanes Ridge

Abstract

HEAT flow measurements were made during a crossing of the North Atlantic from Nova Scotia to Iceland on R/V Trident of the University of Rhode Island, Cruise 41, in August–September 1967. Ten heat flow values were obtained on the crest of the Reykjanes Ridge near 60° N and 30° W. Temperature gradients were measured using the Ewing type thermograd instrument¹ modified at MIT by A. J. Erickson. The instrument consists of the temperature recorder and six thermistors: five of these are separated by 38 cm on the core barrel of a gravity corer. To measure the absolute water temperature, the sixth thermistor was mounted on the weight stand which remained above the water-sediment interface. The recorder was attached to the cable about 15 m above the weight stand. Three or four temperature probes, which penetrated 100–200 cm of the sediment, sufficed to determine the thermal gradient unambiguously (Fig. 1). The thermal conductivity of the sediments was measured by the needle probe method² on the ship after the sediments had reached room temperature and within 2 days of recovering the core. Mean thermal conductivity, obtained by averaging reciprocally the thermal conductivities measured every 10 cm on the relevant portion of the core, was combined with the thermal gradient to give the heat flow. The heat flow values were not corrected for the possible effect of seawater temperature fluctuation which was shown to be influential on heat flow in the Denmark Strait north-west of Iceland³.