Patterns of kinetic energy conversion in a time-average upper ocean

Abstract

Patterns of the spatial fluxes and conversion of oceanic kinetic energy are explored using a 26-year temporal average of a dynamically consistent ECCO state estimate. Because thermal-wind balance is found to be accurate over much of the ocean domain, and with correspondingly small Rossby numbers, a linear analysis is used. Despite the averaging the abyssal ocean average proves remarkably noisy, and thus the focus is on the upper ocean and using the surface layer to 50 m, and depths of 300, 2000, and 3000 m as representative. Surface patterns to 300 m are broadly consistent with what is expected from wind-forcing via Ekman layers. At 2000 m, north of the equator, the flow of North Atlantic Deep Water is dominated by interior flow, and not by the western boundary current used in some over-simplified descriptions. By 3000 m, fluxes are spatially intricate, and presumed to represent the effects of incompletely resolved topographic features. Deep western boundary currents are prominent in kinetic energy, with the surprising exception of the northern North Atlantic and have a complex structure. The complexity of the oceanic container (topography and lateral boundaries) controls much of the circulation when averaged over decades.