Autonomous front tracking by a Wave Glider

Coastal upwelling brings cooler, saltier, and nutrient-rich deep water upward to the surface. Upwelling fronts support enriched phytoplankton and zooplankton populations, thus having great influences on ocean ecosystems. We have developed a method to enable a Wave Glider (an autonomous surface vehicle) to autonomously detect and track an upwelling front. Unlike an autonomous underwater vehicle (AUV) which runs on a yo-yo trajectory to measure vertical profiles of water properties, a Wave Glider's measurements are confined to the surface (from the “float”) and a fixed depth of only several meters (from the submerged “glider”). However, an upwelling front presents a strong surface signature that a Wave Glider can detect. Because the upwelling process brings up cold water from depth, surface temperature in an upwelling region is considerably lower than that in stratified water. A Wave Glider can detect the upwelling front based on the horizontal gradient of the near-surface temperature. We have tested the algorithm by using previous AUV data (only using near-surface temperature measurements) and Wave Glider data. We plan to run field experiments in the summer of 2016 and report the results in the presentation.