On production and dissipation of thermal variance in the oceans

Abstract

An integral relationship is derived expressing the total dissipation of thermal variance by oceanic microstructure in terms of the large-scale forcing at the ocean surface by air/sea heat exchange. The net heat gain by the ocean over warm water and heat loss over cold water is evaluated using zonal averages of annual oceanic heat fluxes and temperatures between 60°N and 60°S. If thermal dissipation occurs in the upper ocean, with a scale depth of 600 m, the average dissipation χ is estimated to be 10- 7 °C2 s- 1. This value compares favorably with published observations of oceanic microstructure dissipation. The prediction is independent of any dynamical model of turbulent cascade from large to small scales in the ocean.