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Abstract:
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The present investigation may be regarded as a part of a systematic effort to introduce
into meteorology and physical oceanography methods and results which for a
number of years have contributed to the rapid growth and increasing practical significance
of experimental fluid mechanics. This science has recognized that the exact character
of the forces controlling the motion of a turbulent fluid is not known and that
consequently there is very little justification for a purely theoretical attack on problems of a practical character. For this reason fluid mechanics has been forced to develop a research technique all of its own, in which the theory is developed on the basis of experiments and then used to predict the behavior of fluids in cases which are not accessible
to experimentation. In oceanography it has long been regarded as an axiom that the movements of the
water are controlled by three forces, the horizontal pressure gradient, the deflecting force,
and the frictional force resulting from the relative motion of superimposed strata. It is
significant that thirty-five years of intensive theoretical work on this basis have failed
to produce a theory capable of explaining the major features of the observed oceanic
circulation below the pure drift current layer. The present investigation considers a force which has been completely disregarded
by theoretical investigators although its existence has been admitted implicitly by
practically everyone who has approached physical oceanography from the descriptive
side, namely the frictional force resulting from large-scale horizontal mixing. The intro-
. duction of this force permits us to see how motion generated in the surface layers may be
diffused and finally dissipated without recourse to doubtful frictional forces at the bottom
of the ocean. |