Abstract
This paper considers the general ocean circulation (GOC) within the thermodynamical closure of our climate theory, which aims to deduce the generic climate state from first principles. The preceding papers of this theory have reduced planetary fluids to warm/cold masses and determined their bulk properties, which provide prior constraints for the derivation of the upper-bound circulation when the potential vorticity (PV) is homogenized in moving masses. In a companion paper on the general atmosphere circulation (GAC), this upper bound is seen to reproduce the observed prevailing wind, therefore forsaking discordant explanations of the easterly trade winds and the polar jet stream. In this paper on the ocean, we again show that this upper bound may replicate broad features of the observed circulation, including a western-intensified subtropical gyre and a counter-rotating tropical gyre feeding the equatorial undercurrent. Since PV homogenization has short-circuited the wind curl, the Sverdrup dynamics does not need to be the sole progenitor of the western intensification, as commonly perceived. Together with GAC, we posit that PV homogenization provides a unifying dynamical principle of the large-scale planetary circulation, which may be interpreted as the maximum macroscopic motion extractable by microscopic stirring, within the confines of thermal differentiation.
Highlights
With the advent of satellite imaging, teeming eddies have emerged as a defining characteristic of the ocean motion field [1], but despite the seemingly random motion, the time-averaged flow exhibits a persistent large-scale structure, which defines the general ocean circulation (GOC, all acronyms are listed in Appendix A) of our inquiry
The GOC simulated by primitive-equation models naturally has retained the Sverdrup remnant, but a recent eddy-resolving experiment of zero wind [3] suggests that Sverdrup dynamics is not needed to produce a subtropical gyre, a tantalizing claim that is aligned with our view, but with an important caveat
Since potential vorticity (PV) homogenization has short-circuited the wind curl to fully remove the vestige of the Sverdrup balance, the latter need not be the sole progenitor of the western intensification, as commonly perceived
Summary
With the advent of satellite imaging, teeming eddies have emerged as a defining characteristic of the ocean motion field [1], but despite the seemingly random (microscopic) motion, the time-averaged (macroscopic) flow exhibits a persistent large-scale structure, which defines the general ocean circulation (GOC, all acronyms are listed in Appendix A) of our inquiry. Because of the inherent coupling of the two, such divisions are somewhat artificial, and the GOC can be explained only as a single manifestation of the coupled field This coupling is considerably simplified when the thermal field is condensed into an outcropped thermocline and the macroscopic motion is limited to that of the warm layer—a configuration that is highly discernible in the observed ocean, as attested by the widespread use of reduced-gravity models. While such layer simplification is justified, the commonly employed laminar dynamics is not, as it suffers from two glaring deficiencies.
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