Available potential energy: a clarification.

R. O. Reid, B. A. Elliott, D. B. Olson

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


In order to clarify some inconsistencies in the literature on ocean energetics, the evaluation of the available potential energy (APE) is reconsidered. Attention is focused on the baroclinic APE under conditions in which the hydrostatic aproximation prevails. Following Margules and Lorenz we define this as the difference between the total enthalpy of a given sample state of the fluid and that of an isentropically leveled state having the same mass. It is partly gravitational potential energy and partly elastic internal energy. For emphasis, we denote this as the ML APE. It differs from the gravitational part (APESUPg), by an amount that depends on whether the elastic internal energy is released (as in the atmosphere) or stored (as in the ocean) during an isentropic leveling process. In the ocean ML APE is found to be somewhat less than the APESUPg, in contrast to the atmosphere where the ML APE greatly exceeds the APESUPg. This difference is ascribed to the temperature dependency of compressibility, which has opposite sign as well as different magnitude for sea water as compared to air.

Original languageEnglish (US)
Pages (from-to)15-29
Number of pages15
Issue number1 , Jan. 1981
StatePublished - 1981
Externally publishedYes

ASJC Scopus subject areas

  • Oceanography


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