Abyssal recipes

Abstract

Vertical distributions in the interior Pacific (excluding the top and bottom kilometer) are not inconsistent with a simple model involving a constant upward vertical velocity w ≈ 1·2 cm day−1 and eddy diffusivity к ≈ 1·3 cm2sec−1. Thus temperature and salinity can be fitted by exponential-like solutions [к · d2/dz2 − w · d/dz] T,S = 0, with к/w ≈ 1 km the appropriate “scale height.” For Carbon 14 a decay term must be included, [ ] 14C = μ 14C; a fitting of the solution to the observed 14C distribution yields (ifк/щ2≈ 200 years for then appropriate “scale time,” and permits ω and к to be separately determined. Using the foregoing values, the upward flux of Radium in deep water is found to be roughly 1·5 × 10−1 g cm−1 sec−1, as compared to 3 × 10−21 g cm−2 sec sedimentary measurements by Goldberg and Koide (1963). Oxygen consumption is computed at 0·004 (ml/l) year−1. The vertical distributions of T,S, 14C and O2 are consistent with the corresponding south-north gradients in the deep Pacific, provided there is an average northward drift of at leat a few millimetres per second.How can one meaningfully interpret the inferred rates of upwelling and diffusion? The annual freezing of 2·1 × 1019 g of Antarctic pack ice is associated with bottom water formation in the ration 43 : 1, yielding and estimated 4 × 1020g year−1 of Pacific bottom water ω = 1·2 cm day−1 implies 6 × 1020g year−1. I have attemped, wiothout much success, to interpret к froma variety of viewpoints: from mixing along the ocean boundaries, from thermodynamic and biological processes, and from internal tides. Following the work of Cox and Sandstrom (1962), it is found that surface tides are scattered by the irregular bottom into modes with an associated energy flux of 4 × 10−6 ergs g−1 (one sixth total tidal dissipation). Such modes can produce shear instability in the Richardson sence. It is found that internal tides provides a marginal but not impossible mechanism for turbulent diffusion in the interior oceans.