Ocean front detection and tracking by an autonomous underwater vehicle

In this paper we present a method of using an autonomous underwater vehicle (AUV) to detect and track an ocean front created by coastal upwelling. In an upwelling water column, temperature, salinity, and other properties are more homogeneous over depth as compared with non-upwelling water which is typically stratified. We use the vertical homogeneity of temperature as the classifier for differentiating upwelling and stratified water columns. On 27 April 2011, the Tethys long-range AUV ran the algorithm to autonomously detect and track a front in a dynamic coastal upwelling region in Monterey Bay, CA. The AUV transected the front 14 times over two days, providing a very high-resolution depiction of the front.

I. Introduction

An ocean front delineates the boundary between water masses distinguished by different physical, chemical, and/or biological characteristics. Ocean ecosystems are greatly influenced by the structure and dynamics of fronts [1]. Ocean fronts also play an important role in air-sea exchange [2], [3]. Detection and tracking of ocean fronts is important for investigating the formation, evolution, and interaction of ocean water masses. Knowing the boundary between these water masses enables targeted sampling of the respective waters.