Abstract:

Data is from the Navy Coastal Ocean Model (NCOM) Version 4.3 (Martin et al., 2009). The model uses a staggered Arakawa-C grid that extends from 18°N to 31°N and 98°W to 79°W with a 3 km horizontal resolution on a spherical projection. In the vertical, there is a 35 layer terrain-following (free-sigma) grid on top of 15 z-levels, with bottom cells "shaved" as needed to match bathymetry, such that within the Loop Current region, the surface and bottom cells are approximately 0.5 and 500 m thick, respectively. Vertical mixing is parameterized using the Mellor-Yamada Level 2 closure model (Mellor & Yamada, 1974, 1982). A logarithmic bottom boundary layer is assumed, and bottom drag is computed with a spatially constant parameter of 1 cm. All advection schemes are 2nd order and no tidal forcing is prescribed. Open boundary conditions are specified by the global 1/12 degree 41-layer Hybrid Coordinate Ocean Model (HYCOM) with the Naval Research Lab Coupled Ocean Data Assimilation (NCODA) System, together known as the Global Ocean Forecasting System (GOFS) version 3.1 (Metzger et al., 2014). The model was initiated from the year 2018. Deep temperature and salinity fields were relaxed to the U.S. Navy Generalized Digital Environment Model (GDEM) version 3.0 (Carnes et al., 2010). Meteorological forcing is from the Navy Global Environmental Model (Hogan et al., 2014). The model integration is not run with data assimilation. Instead our purpose is to illustrate the free-running dynamics that occur within the whole water column around the LC during its naturally occurring extension, detachment/reattachment, and separation cycle. References: Carnes, M. R., Helber, R. W., Barron, C. N., & Dastugue, J. (2010). Validation test report for GDEM4. Rep. NRL/MR/7330-10 , 9271 . Hogan, T. F., Liu, M., Ridout, J. A., Peng, M. S., Whitcomb, T. R., Ruston, B. C., . . . others (2014). The navy global environmental model. Oceanography, 27 (3), 116–125. Martin, P. J., Barron, C. N., Smedstad, L. F., Campbell, T. J., Wallcraft, A. J., Rhodes, R. C., . . . Carroll, S. N. (2009). User’s manual for the Navy Coastal Ocean Model (NCOM) version 4.0 (Tech. Rep.). NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEAN DYNAMICS AND PREDICTION BRANCH. Mellor, G. L., & Yamada, T. (1974). A hierarchy of turbulence closure models for planetary boundary layers. Journal of the atmospheric sciences, 31 (7), 1791–1806. Mellor, G. L., & Yamada, T. (1982). Development of a turbulence closure model for geophysical fluid problems. Reviews of Geophysics, 20 (4), 851–875. Metzger, E. J., Smedstad, O. M., Thoppil, P. G., Hurlburt, H. E., Cummings, J. A., Wallcraft, A. J., . . . others (2014). US Navy operational global ocean and Arctic ice prediction systems. Oceanography, 27 (3), 32–43.