Deep-water temperatures in the FAMOUS area

Abstract

Some of the results of Project FAMOUS studies, which were undertaken in the axial area of the Mid-Atlantic Ridge between approximately 36/sup 0/30' and 37/sup 0/N latitudes, are reported. The distribution of water temperatures in the FAMOUS area was investigated during the years 1972 to 1974. Forty-seven vertical temperature profiles were taken and bottom-water temperature measurements along 110 km of traverses were carried out during the course of four cruises. Potential temperatures in the FAMOUS area were found to range between 3.53 and 3.85/sup 0/C below a depth of 2,200 m. These temperatures are almost 1/sup 0/C higher than temperatures outside the axial zone of the Mid-Atlantic Ridge at comparable depths. The potential temperature in deep waters was observed to increase from 3.53/sup 0/C in the western part of fracture zone B to 3.80/sup 0/C in the eastern part of fracture zone A. Vertical temperature gradients are smaller than 1 x 10/sup -4/ /sup 0/C/m at depths below 2,200 m in the various basins of the FAMOUS area. Between 2,000 and 1,800 m, the temperature differences between the different parts of the area gradually disappear; above 1,500 m, there are no significant differences between water temperatures in the ridge andmore » those in the surrounding ocean. The observed near-bottom temperature distribution in the FAMOUS area is related to the bottom topography. The temperatures in the various basins are determined mainly by their sill depth; the observed south-north increase of deep-water temperatures and the velocity of bottom-water currents in the area can be related quantitatively to hydrologic effects. The influence of hydrothermal activity and of heat flow through the ocean floor on the temperature distribution in the area is negligible.« less