Empirical evidence of a fluctuation theorem for the wind mechanical power input into the ocean

Type Article
Date 2021-08
Language English
Author(s) Wirth AchimORCID1, Chapron Bertrand2
Affiliation(s) 1 : Univ. Grenoble Alpes, CNRS, Grenoble INP, LEGI, 38000 Grenoble, France
2 : LOPS, Ifremer, Plouzané, France
Source Nonlinear Processes In Geophysics (1023-5809) (Copernicus GmbH), 2021-08 , Vol. 28 , N. 3 , P. 371-378
DOI 10.5194/npg-28-371-2021

Ocean dynamics is predominantly driven by the shear stress between the atmospheric winds and ocean currents. The mechanical power input to the ocean is fluctuating in space and time and the atmospheric wind sometimes decelerates the ocean currents. Building on 24 years of global satellite observations, the input of mechanical power to the ocean is analysed. A fluctuation theorem (FT) holds when the logarithm of the ratio between the occurrence of positive and negative events, of a certain magnitude of the power input, is a linear function of this magnitude and the averaging period. The flux of mechanical power to the ocean shows evidence of a FT for regions within the recirculation area of the subtropical gyre but not over extensions of western boundary currents. A FT puts a strong constraint on the temporal distribution of fluctuations of power input, connects variables obtained with different lengths of temporal averaging, guides the temporal down- and up-scaling and constrains the episodes of improbable events.

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