Deep flow variability in the vicinity of the Yucatan Straits from a high‐resolution numerical simulation

Abstract

The deep flow variability in the vicinity of the Yucatan Channel between the Caribbean Sea and the Gulf of Mexico is examined within a high‐resolution numerical simulation of the North Atlantic Ocean. We focus on the 6 year integral cycle of Loop Current (LC) ring formation, and we study the flow regimes both in the Yucatan Channel and farther north in the LC. The circulation in the vicinity of the Yucatan Channel presents a high variability in the flow regimes and in the shedding period, in good agreement with earlier observations. The outflow (toward the Caribbean Sea) in the Yucatan Channel is shown to be controlled in part by a regular shift of the LC maximum velocity position, in phase with the transport variations. The outflow follows the inflow variations independently of the northward extension of the LC. Our analysis of the growth of the loop is also shown to be in good agreement with the ballooning process proposed by Pichevin and Nof (1997) and Nof and Pichevin (2001) to explain the LC ring formation. Moreover, at the end of each cycle of ring formation a sudden deepening of the LC deepest layer occurs together with an intensification of the transport and of the currents in the deep layers beneath the LC. This process is shown to be connected with the growth of cyclones in the deep layers. They result from the bottom‐intensified instability of the LC ring and contribute to its separation from the LC.