Consideration of the depth of the motionless surface near the grand banks of Newfoundland

In physical oceanography the admitted limitations of the Bjerknes circulation theorem sometimes are lost sight of and therefore the current trend of inquiring emphasis on these limitations is encouraging. The intelligent interpretation of dynamic calculations and the determination of absolute current directions and velocities therefrom, depend upon a knowledge of the location and shape of a motionless reference surface. In the past the arbitrary selection of isobaric surfaces for reference has been the resort to an
approximation found useful in the absence of more definite knowledge regarding the true location and shape of such a motionless surface or surfaces. In recent years various oceanographers have proposed various non-spheroidal reference surfaces such as the oxygen-minimum layer, and a surface approximating an isentrope of constant vertical stability. The state of our knowledge has not yet reached the point where we can define such a surface which is universally applicable. Until that stage of development is reached each unique region must be dealt with individually and the several particular solutions may help in ultimately laying bare that general solution.