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Seasonality of the submesoscale dynamics in the Gulf Stream region |
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| Authors: | Jean Alberto Mensa Zulema Garraffo Annalisa Griffa Tamay Mehmet Özgökmen Angelique Haza Milena Veneziani |
| Institution: | 1. RSMAS, University of Miami, 4600 Rickenbacker Csw, Miami, FL, 33149-1098, USA 2. IMSG at NOAA/EMC, NCWCP, 5830 University Research Court, College Park, MD, 20740, USA 3. ISMAR/CNR, U.O.S di Pozzuolo di Lerici (SP), Forte Santa Teresa, 10932, Lerici, La Spezia, Italy 4. Division T-3 MSB216, Fluid Dynamics and Solid Mechanics, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA |
| Abstract: | Frontogenesis and frontal instabilities in the mixed layer are known to be important processes in the formation of submesoscale features. We study the seasonality of such processes in the Gulf Stream (GS) region. To approach this problem, a realistic simulation with the Hybrid Coordinate Ocean Model is integrated for 18 months at two horizontal resolutions: a high-resolution (1/48°) simulation able to resolve part of the submesoscale regime and the full range of mesoscale dynamics, and a coarser resolution (1/12°) case, in which submesoscales are not resolved. Results provide an insight into submesoscale dynamics in the complex GS region. A clear seasonal cycle is observed, with submesoscale features mostly present during winter. The submesoscale field is quantitatively characterized in terms of deviation from geostrophy and 2D dynamics. The limiting and controlling factor in the occurrence of submesoscales appears to be the depth of the mixed layer, which controls the reservoir of available potential energy available at the mesoscale fronts that are present most of the year. Atmospheric forcings are the main energy source behind submesoscale formation, but mostly indirectly through mixed layer deepening. The mixed layer instability scaling suggested in the (Fox-Kemper et al., J Phys Oceanogr 38:1145–1165, 2008) parametrization appears to hold, indicating that the parametrization is appropriate even in this complex and mesoscale dominated area. |
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