Multi-Scale Satellite Observations of Lagrangian Coherent Structures in Ocean Flows

• Amy Duh, Marine Science, University of Delaware

• Matthew Oliver, School of Marine Science & Policy, University of Delaware

Lagrangian Coherent Structures (LCSs) are significant features in ocean flows that act as pathways guiding the natural accumulation of nutrients, plankton, and other drifting materials. These structures can be detected by analyzing satellite data, specifically looking at the Finite-Time Lyapunov Exponent (FTLE), using the programming language R. FTLE is the measurement of how quickly water particles are separating over time, meaning high FTLE values indicate the presence of LCS. This research aims to discover where LCS are located and most concentrated across the globe. R is used to create global images showing FTLE across two different scales: spatial and temporal. The multi-scale datasets are averaged at different spatial and temporal resolutions, representing various distances (9, 50, 100, 500 km) and time (8, 30, 365 day) intervals. Selecting the appropriate combinations of resolutions allows for comparison of both small- and large-scale maps to determine the most effective images for a specific project. These colored images help identify where LCSs are strong and predictable on the ocean surface. Preliminary results show that LCSs are more concentrated near the poles and less near the equator, which is likely due to the influence of the Coriolis effect and wind-driven currents. The ability to discover high LCS locations benefits fisheries and other marine studies, as it can improve fish forecasting and enable the identification of the nutrient-rich zones on the sea surface. Furthermore, it can enhance our understanding of whether LCS is affecting predator behavior and distribution, as high LCS areas imply greater nutrient availability, attracting more prey and predators. Future research will explore how marine animals locate, memorize, and revisit these LCS areas as their consistent food sources. Connecting physical flow images with biological tracking data could provide deeper insight into marine organism behavior, migratory patterns, and ecosystem dynamics.