Energetics of the global ocean: The role of mesoscale eddies

Hidenori Aiki (Lead Author), Xiaoming Zhai, Richard J. Greatbatch

Research output: Chapter in Book/Report/Conference proceedingChapter (peer-reviewed)

9 Citations (Scopus)
12 Downloads (Pure)

Abstract

This article reviews the energy cycle of the global ocean circulation, focusing on the role of baroclinic mesoscale eddies. Two of the important effects of mesoscale eddies are: (i) the flattening of the slope of large-scale isopycnal surfaces by the eddy-induced overturning circulation, the basis for the Gent–McWilliams parametrization; and (ii) the vertical redistribution of the momentum of basic geostrophic currents by the eddy-induced form stress (the residual effect of pressure perturbations),
the basis for the Greatbatch–Lamb parametrization. While only point (i) can be explained using the classical Lorenz energy diagram, both (i) and (ii) can be explained using the modified energy diagram of Bleck as in the following energy cycle. Wind forcing provides an input to the mean KE, which is then transferred to the available potential energy (APE) of the large-scale field by the wind-induced Ekman flow. Subsequently, the APE is extracted by the eddy-induced overturning circulation to feed the mean KE, indicating the enhancement of the vertical shear of the basic current. Meanwhile, the vertical shear of the basic current is relaxed by the eddy-induced form stress, taking the mean KE to endow the eddy field with an energy cascade. The above energy cycle is useful for understanding the dynamics of the Antarctic Circumpolar Current. On the other hand, while the source of the eddy field energy has become clearer, identifying the sink and flux of the eddy field energy in both physical and spectral space remains major challenges of present-day oceanography. A recent study using a combination of models, satellite altimetry, and climatological hydrographic
data shows that the western boundary acts as a “graveyard” for the westward-propagating eddies.
Original languageEnglish
Title of host publicationIndo-Pacific Climate Variability and Predictability
EditorsSwadhin Behera, Toshio Yamagata
PublisherWorld Scientific
Pages109-134
Number of pages26
ISBN (Electronic)978-981-4696-63-0
ISBN (Print)978-981-4696-61-6
Publication statusPublished - Feb 2016

Publication series

NameAsia-Pacific Weather and Climate
PublisherWorld Scientific
Volume7

Cite this