The Influence of Icebergs on the Temperature of the Sea

Abstract

IN the early 'seventies of last century I took considerable interest in oceanic circulation. Dr. Carpenter had previously shown that when the warm water moves from the equator towards the poles it gradually cools and sinks near the poles, and he showed that when this current meets with icebergs they have a cooling effect and produce downward currents; this he illustrated by placing some ice at one end of a tank of sea water, when a downward current was produced under the ice, which flowed away along the bottom of the tank towards the other end, where it rose and flowed back along the surface towards the ice. In 1873 I pointed out that Dr. Carpenter's description of the two currents did not give a full statement of what was taking place; that his surface current was not at the surface, but only near it, and that above it was another formed of a mixture of sea water and the fresh water of the melted ice, which had a lower specific gravity, though colder, than the sea water. This cold water flowed away from the ice over the surface of the warmer water. That the ice-cooled sea water was lighter than the sea water was also shown by dividing the experimental tank into two parts by means of a movable vertical partition. The water in one half was cooled by means of ice in varying amounts, and on removing the partition the cold water always flowed over the hot.