Numerical simulation of the Gulf Stream System: The Loop Current and the deep circulation

Loop Current, Rings and Related Circulation in the Gulf of Mexico: A Review of Numerical Models and Future Challenges

“…The bottom boundary layer plays a crucial role as Ekman pumping serves to link the mean current with the Reynolds stresses of the wave field. If we take the typical TRW characteristics in the Gulf, and the bottom slope [e.g., Oey and Lee, 2002] Lee and Mellor's [2003] work, and support their findings by noting that the mean currents computed from PALACE floats at z = −900 m are also generally cyclonic. The PALACE mean currents show a more erratic picture but one can generally discern westward flow in the north central Gulf, southward mean in the west/northwest, a cyclonic gyre in the southwestern Gulf (i.e., the Campeche Bay), and broad eastward flow off the northern Campeche shelf at 90 o W, from 23 o N~26 o N, and westward flow further north around 27 o N; the flows are more clearly defined in the west and southwest, but contain smaller-scale features in the central Gulf.…”

“…Thirteen rings were tracked for the 8 year simulation (after a 2-year spin-up), giving an averaged shedding period ≈ 7.5 months, slightly longer than Sturges et al' [Hamilton,990;200]. Oey and Lee [2002] examined details of deep energy generated by Loop Current variability and rings in the model described above in conjunction with Oey et al's [2003] Lee and Mellor [2003] using also POM but forced by the NCEP-Eta wind. These latter authors also confirm the cyclonic deep circulation.…”

“…Vazquez de la Cerda et al's (this volume) analyses of hydrographic, drifter, floats and satellite data lend further supports that the mean circulation in the Campeche Bay is cyclonic. In light of these observational analyses, future work should extend Oey and Lee's [2002] and Lee and Mellor's [2003] calculations with runs using different forcing, grid-resolution and eddy viscosities, and analyzing dynamics and comparing the results with observations. It is likely that deep flows in the Gulf are TRW and eddy-driven: reminiscence of currents with banded structures seen in idealized studies of geostrophic eddies and turbulence [e.g.…”

Argo data assimilation into HYCOM with an EnOI method in the Atlantic Ocean

“…These are regions of strong gradients, variability and mesoscale eddy activity. The Gulf Stream is highly influenced by mesoscale circulation and the growth of baroclinic instability after its separation from the North American coast (Robinson et al, 1989;Spall and Robinson, 1990;Lee and Mellor, 2003). Also, the Brazil-Malvinas Confluence is characterized by a weak and warm southward Brazil Current meeting a strong, cold and less saline northward Malvinas Current, which results in large contrasts in stratification and strong eddy activity (Gordon, 1989;Garzoli and Garrafo, 1989;Goni et al, 1996).…”

“…Second, the purpose of this grid is to provide reasonable boundary conditions to higher-resolution grids that will soon be configured along the Brazilian coast, which is the area of main interest to REMO and far away from the northern boundary. On the lateral boundaries, relaxation to monthly climatological temperature and salinity from Levitus (1982) was applied considering the outermost 10 grid cells and the timescale of 30 days. This approach attempts to preserve climatological shear through geostrophic adjustment and has been successfully used in previous works (e.g., Paiva and Chassignet, 2001;Gabioux et al, 2013).…”