On the Color of the Sea

Abstract
Color of seas and lakes cannot be explained either by (1) the intrinsic color of water due to selective absorption f(λ), or by (2) the Rayleigh scattering by microscopic particles or bubbles of gas 12αλ4, alone. A combination of these two causes, however, together with (3) selective reflection ϕ(λ) by larger particles (clay, plankton, etc.) and (4) light reflected from the sky, seems to be adequate, if the effect of waves is taken into account. The general theory is developed, and then, using experimentally determined values of the selective reflection ϕ(λ) for a brown clay suspension, curves are computed for various values of the proportion of such particles β, and for the scattering coefficient α, which give resultant colors varying from green to brown, as determined by optical synthesis. By the use of a colloidal solution of rosin in alcohol colored with Redulin blue, a model of the sea was made which gave spectrophotometric curves agreeing closely with the theory. The theory of the Secchi disk is given and the relation between the coefficient of diffusion α and the maximum depth at which the disk is visible. Coefficients computed from disk observation for various lakes agree with those obtained from the spectral distribution curves of Aufsess.—G. S. F.