Analyzing Turbulent Flow in an Idealized Section of the Samoan Passage

Abstract

The Samoan Passage, a key conduit for Antarctic Bottom Water (AABW) into the North Pacific Basin, facilitates abyssal mixing through internal hydraulic jumps and turbulence. Regions of intense mixing were found downstream of a hydraulically controlled sill in the Samoan Passage. This mixing is important, as flow from PMOC keeps the Samoan Passage fed with dense abyssal waters, creating one of the few locations for deep water modification. The topography of the northern sill in the Samoan Passage (denoted P5), combined with unique forcing of abyssal waters, drives persistent and young overturns to dominate and modify the deepest waters of the Pacific Ocean. Age of overturns and intensity of mixing are determined by the ratio of the Thorpe length scale and Ozmidov length scale. The Thorpe scale (LT) represents the root-mean-square (rms) displacement of overturns, and the Ozmidov scale (LO) indicates the largest eddies unaffected by buoyancy. Results reaffirm previous studies that suggest great amounts of abyssal mixing exist in the Samoan Passage, and the modification could impact the properties and behavior of the Global Meridional Overturning Circulation (GMOC). The research contributes to understanding abyssal mixing in the Samoan Passage, offering insights for oceanographers studying similar bathymetric features, providing a simplified model for education, and advancing predictions of the natural world.