SGER: Generation of Eddies by Oceanic Islands: A Laboratory Study

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Abstract OCE-0723769Intellectual Merit: For many decades, mesoscale eddies have been observed near some oceanic islands. These eddies have been regions of suspected enhanced biological production. It has been speculated that the eddies are generated by the current flowing past the island when the current is sufficiently strong. For some islands which have tall mountains, it has been postulated t hat the winds deflected by the island can produce the eddies through Ekman pumping in the lee of the island. However, while there have been observations of the eddies, there has not been a comprehensive study to examine the generation mechanism of the eddies and their initial evolution. In this project, a series of laboratory experiments of fluid flow around a cylinder (representing an island) will be undertaken. In addition, a spatially varying stress will be applied to the fluid in some of the experiments. These two sets of experiments represent the two possible eddy formation mechanisms in the lee of an island. The three-dimensional velocity near the surface will be determined using particle image velocimetry. These data will allow us to examine the dynamics of the generation of the eddies and their initial evolution as the eddies are advected away from the cylinder. The response to a range of island diameters and stratification will be investigated.Broader Impacts:This project will improve our understanding of mesoscale and submesoscale dynamics of the ocean and will likely resolve some of the prevailing hypotheses related to eddy formation by islands and their influence on biological productivity. A close collaboration with scientists in Spain who have studied the influence of eddies on the ecosystem dynamics around the Canary Islands will be established. Collaborations with modelers interested in studying the generation of eddies by islands will also be pursued.