Collaborative Research: What Do Global Surface Drifters Tell Us About Submesoscale Processess?

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).A recent global census of surface loopers (drifter trajectories with a definite sense of rotation) has revealed some unexpected features of the distribution of structures at scales of the submesoscale (R15 km; Griffa, Lumpkin, and Veneziani 2008). Three main regimes have emerged: a) a prevalently cyclonic zonal band at 10−20 degrees latitude; b) a prevalently anticyclonic zonal band at 30−40 degrees and c) regions devoid of submesoscale presence corresponding to areas of formation of great rings. The dynamical mechanisms behind this distribution are not completely understood yet, one of the reasons being that small loopers can be the signature of different processes, such as submesoscale eddies and subinertial Ekman response.This study focuses on the submesoscale component, and investigates the implications of the findings for submesoscale distribution in the open ocean. The question to be addressed is: Are submesoscale processes in the world ocean characterized by a nontrivial distribution in terms of polarity and abundance, modulated by the ambient large-scale dynamical regimes in which they form? This question cannot be investigated by means of Lagrangian data alone, and other global data sets or global numerical models do not have sufficient spatial and temporal resolution to solve submesoscale structures. Therefore very high resolution (up to 300 m) regional models of key selected areas suggested by the drifters will be used to investigate the Eulerian and Lagrangian dynamics. This will be complemented by specific process studies in idealized configurations indicated by the regional modeling results. The overall result will be an increased understanding of the properties and distribution of open ocean submesoscale processes.The proposed research has a societal impact because it contributes to the understanding of climate and biological processes in the upper ocean. The results will be presented in graduate classes at UCSC and RSMAS, and they will be part of outreach programs. Analysis algorithms developed for the ROMS model simulations will be freely distributed to the greater scientific community through the WikiROMS web-pages.