On the momentum transfer at the sea surface. I. On the frictional force between air and water and on the occurrence of a laminar boundary layer next to the surface of the sea. II. Measurements of vertical gradient of wind over water. III. Transport of surface water due to the wind system over the North Atlantic

Abstract

I. It is fairly generally assumed that the horizontal circulation of the ocean "troposphere" is maintained by the large scale permanent wind system of the atmosphere. Accurate knowledge of the tangential force exerted by the wind on the surface of the water should therefore be a prerequisite for every attempt to analyze the movements of the surface water. Very few data are available from which this shearing force may be accurately determined, although several, in principle simple, methods of attack are available. Recently some estimates of the wind force have appeared in studies not primarily concerned with the oceanographic aspects of the problem. In view of the conflicting results obtained and in view of the importance of the problem to physical oceanography it seems desirable to examine the question theoretically and to study critically the empirical determinations just referred to. II. Despite the great importance, in studies of the frictional forces between atmosphere and ocean, of wind gradient measurements next to the ocean surface, to my knowledge the only observations that have been published are those of Wüst and of Shoulejkin. Both of these are so fragmentary that one would find it very difficult to draw general conclusions from them alone. Feeling that further measurements of any sort might prove useful, and lacking time and facilities for a large program, the author felt justified in making the following simple measurements during September 1935, which may be regarded as preliminary. III. The results of Section I above and of our previous paper are here applied to the specific computation of the transport of the drift current system over the North Atlantic. Only the computation is given here, but the authors of this paper expect to discuss in later articles its significance in connection with the surface salinity distribution and with the Equatorial Current.