Laboratory experiments reveal intrinsic self-sustained oscillations in ocean relevant rotating fluid flows

Stefano Pierini,Maria Eletta Negretti,Paola De Ruggiero,Samuel Viboud,Henk A Dijkstra,Julia Weiffenbach,Thomas Valran,Joël Sommeria,Ilana Schiller-Weiss

doi:10.1038/s41598-022-05094-1

Abstract

Several ocean Western Boundary Currents (WBCs) encounter a lateral gap along their path. Examples are the Kuroshio Current penetrating into the South China Sea through the Luzon Strait and the Gulf of Mexico Loop Current leaping from the Yucatan peninsula to Florida as part of the Gulf Stream system. Here, we present results on WBC relevant flows, generated in the world’s largest rotating platform, where the Earth’s sphericity necessary to support WBCs is realized by an equivalent topographic effect. The fluid is put in motion by a pump system, which produces a current that is stationary far from the gap. When the jet reaches the gap entrance, time-dependent patterns with complex spatial structures appear, with the jet leaking, leaping or looping through the gap. The occurrence of these intrinsic self-sustained periodic or aperiodic oscillations depending on current intensity is well known in nonlinear dynamical systems theory and occurs in many real systems. It has been observed here for the first time in real rotating fluid flows and is thought to be highly relevant to explain low-frequency variability in ocean WBCs.

Highlights

Examples are the Kuroshio Current penetrating into the South China Sea through the Luzon Strait and the Gulf of Mexico Loop Current leaping from the Yucatan peninsula to Florida as part of the Gulf Stream system
In this paper we have presented and discussed the results of laboratory experiments carried out with the world’s largest rotating platform aimed at simulating the behavior of a Western Boundary Current (WBC) encountering a lateral gap along its path
This is a relevant problem in physical oceanography which applies, among others, to two specific cases in the Northern Hemisphere: the Kuroshio Current penetrating into the South China Sea through the Luzon Strait and the Gulf of Mexico Loop Current

Summary

Introduction

This provides the first experimental evidence based on laboratory experiments of SSIV of WBCs, but, more in general, of rotating fluid flows. The great relevance of the problem and the valuable results obtained with a small rotating tank, calls for further laboratory experiments that could possibly reveal SSIV associated with gap-leaping or intruding WBCs in the context of ADDSs. This requires larger scale simulations and, in turn, a larger rotating tank facility.

Results

Conclusion