[A-OS12] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS12-03] Formation and offshore transport of intra-thermocline anticyclonic eddies and filaments in the Peru-Chile EBUS under ENSO forcing

*Gandy Maria Rosales Quintana¹, Takeyoshi Nagai², Luis Alfredo Icochea³ (1.Course of Applied Marine Environmental Studies, Tokyo University of Marine Science and Technology, 2.Department of Ocean Sciences, Tokyo University of Marine Science and Technology, 3.Universidad Nacional Agraria La Molina)

Keywords:Peru-Chile Undercurrent Subsurface Eddies, Offshore Transport, Eddies

Recent numerical studies have shown that subsurface anticyclonic eddies are formed through the low potential vorticity (PV) generation caused by the undercurrents flowing over steep slopes in the eastern upwelling systems. These subsurface eddies are found to transport matters over a long distance. As the low PV generation is often associated with submesoscale instability followed by microscale turbulent mixing, they may contain and transport a large amount of nutrients. Thus, understanding the formation mechanisms and material transport of the intra-thermocline eddies and filaments in the Peru-Chile eastern boundary upwelling system (EBUS) contributes to improve the prediction of marine ecosystem responses to the long-term climate variability. Nevertheless, since these subsurface eddies cannot be seen from the satellite, it has been unclear how much transports occur and how these transports vary interannually. In this study, we use reanalysis (0.083 degree) data from Copernicus Marine Service to detect and track subsurface eddies and filaments, to investigate the modulations of the subsurface eddy kinetic energy (SEKE) from 1993 to 2019 including 2 types of extreme ENSO events (1997-1999 and 2015-2017), and to quantify subsurface eddies originated in the PCUC and the nitrates propagated offshore. If the analyses are ready by the time of the presentation, we will show the results from an ocean-biogeochemical ROMS simulation that realistically simulates mean circulation in the Peru-Chile Undercurrent (PCUC), to quantify subsurface eddies originated in the PCUC and their effect propagated offshore under different ENSO conditions.