Changes in the Loop Current's Eddy Shedding in the Period 2001–2010

Fred M Vukovich

doi:10.1155/2012/439042

Abstract

A major change in the Loop Current's eddy shedding was found in the decade 2001–2010. Sixteen (16) rings separated from the Loop Current in that decade, whereas in two previous decades, 11 rings separated in each decade. More than half the rings (i.e., 56%) that separated from the Loop Current in the decade 2001–2010 had separation periods ≤8 months. In the period prior to 2001, only 26% of the rings had separation periods ≤8 months. Furthermore, the dataset average period for ring separation for the period prior to 2001, an average over a 29-year period, was about 11 months, and the dataset average Loop Current's westward tilt angle—a factor that indicates whether the Loop Current will soon shed an eddy or not—was about 16°. After the year 2000, the dataset average period for ring separation, an average over a 39-year period, decreased by about 1 month and was about 10 months. The average ring-separation period in the decade 2001–2010 was about 9 months. The dataset average of the Loop Current's westward tilt angle increased by about 5° in the period 1998–2008 and was about 20° in 2010. Potential causes for these changes are discussed.

Highlights

Previous studies of the cycle of warm-core ring (WCR) separation from the Loop Current have reported average separation periods of about 11-12 months [1,2,3,4,5,6]
The dataset average period for ring separation for the period prior to 2001, an average over a 29-year period, was about 11 months, and the dataset average Loop Current’s westward tilt angle—a factor that indicates whether the Loop Current will soon shed an eddy or not—was about 16◦
Using a 28-year data set (1976–2003), Vukovich [6] noted that the average westward tilt angle of the Loop Current was about 17◦, which, it was determined from observations, indicated that the Loop Current, on average, was not about to shed a WCR anytime in the very near future

Summary

Introduction

Previous studies of the cycle of warm-core ring (WCR) separation from the Loop Current have reported average separation periods of about 11-12 months [1,2,3,4,5,6]. Using a 28-year data set (1976–2003), Vukovich [6] noted that the average westward tilt angle of the Loop Current was about 17◦, which, it was determined from observations, indicated that the Loop Current, on average, was not about to shed a WCR anytime in the very near future. It was determined from observations that when the Loop Current’s westward tilt angle was >30◦, a WCR would separate from the Loop Current within about 30 to 60 days. The data presented in the literature to date would suggest that over the last 30 or so years, the Loop Current eddyshedding cycle has been relatively consistent with an average period for eddy shedding of about 11-12 months and the Loop Current, on average, was not about to shed a WCR anytime soon (i.e., rings would separate with periods ≥8 months). This paper presents data outlining those changes and discusses the implication of those changes relative to the forces that may affect the Loop Current’s behavior

Data and Procedure

Loop Current Eddy-Shedding Period

Loop Current Orientation

Findings

Summary and Discussion