A novel identification method for unrevealed mesoscale eddies with transient and weak features-Capricorn Eddies as an example

Abstract

Traditional eddy detection methods can well identify eddies with long lifespans (usually >4 weeks) and strong hydrographic features. Eddies with shorter lifespans or intermittent features are arduous to detect and might be eliminated or misclassified during the detection. However, these eddies have been reported as a majority of the mesoscale eddies in global oceans. This study developed a novel eddy identification method for those eddies. Different from the traditional eddy detection performed based on a snapshot of observations in the horizontal plane, this novel identification method was developed on the evolution of eddies in the temporal dimension. It efficiently avoids the failure in detecting eddies with inconspicuous features during some stages of their evolutions and also eliminates excessive detection. The developed method was implemented to detect Capricorn Eddies based on 26 years of sea-level anomaly from satellite altimetry. Capricorn Eddies are transient and intermittent phenomena induced as a result of the East Australian Current colliding with the continental shelf edge near the Fraser Island, Australia. Using the new identification method, the characteristics of Capricorn Eddies, including their temporal and spatial scales, intensity preferences and evolution details, were resolved. Remarkable seasonal variations of the Capricorn Eddies were also revealed. Based on these findings, a comprehensive overview of Capricorn Eddies, which is crucial for further understanding the variabilities of regional biogeochemical processes and ocean ecosystems, was provided. The developed method will also provide potential insight into the unrevealed eddies in the global oceans.