The connectivity of eddy variability in the Caribbean Sea, the Gulf of Mexico, and the Atlantic Ocean

Abstract

Table 1) with 1/2 ø resolution is utilized. After spin-up to statistical equilibrium, all of the simulations were forced by daily averaged winds from 1981 to 1994, so that interannual variability is also present. The formulation for the NLOM is presented in section 2 with detailed equations for the thermodynamic version. The modifications necessary to create a hydrodynamic version are also presented as well as a more detailed discussion of the design of the three simulations specifically used in this study.These simulations contain different physics, which are used to include or exclude dynamical processes that may be relevant to the simulation of mean currents and variability in the Caribbean. For instance, simulation 2 contains realistic bottom topography. Simulation l is reduced gravity and therefore excludes the barotropic mode and the bottom topography. Since eddies are observed in both simulations, these differences provide a means to investigate (1) the influence bottom topography and baroclinic instability involving the barotropic mode on the simulated eddies in the Caribbean and (2) topographic effects on eddy formation and pathways of mean currents. Simulation 1 is also thermodynamic and therefore contains more accurate stratification that can influence eddy generation and propagation speeds. This simulation also has a more accurate representation of the return flow of the global thermohaline circulation, which affects the mean transports through the Lesser Antilles. The linear simulation excludes flow instability dynamics, providing a linear, deterministic ocean model response to the atmospheric forcing. It is used to demonstrate the impact of nonlinearity on a multiyear anomaly seen in the interannual simulations and to isolate the cause of this anomaly.This investigation can be viewed as an attempt to use the model simulations to extend our understanding of a region with limited observations after comparing the simulations with the observational data currently available. However, additional observations are required to adequately assess the model re- The model also includes interfacial friction that is quadratically proportional to the velocity shear between the adjacent layers. In the simulations used here, this type of interfacial friction is excluded by setting Ca = 0. However, an interfacial friction effect is retained via the diapycnal mixing.Three versions of the model were used in this study. Table 1 provides In the model, deepwater formation is parameterized (1) by using ports along the northern boundary with prescribed outflow in the upper ocean and prescribed inflow in the abyssal layer and (2) by downwelling in the Labrador Sea via the oxygen-based cross-interfacial mixing scheme described earlier. Both simulations 1 and 2 have an imposed outflow of 8 Sv in the top five layers at two ports, one located between Greenland and Scotland, the second in the Davis Strait (Table 1) into the Gulf of Mexico. This phenomenon has been simulated in other versions of the NRL model that possess ac...

The Evolution and Demise of North Brazil Current Rings*

“…All available in situ and most remote observations indicate that most NBC rings turn northward upon reaching the shoaling topography east of the Lesser Antilles and pass very near the island of Barbados. While some numerical simulations and satellite altimeter observations suggest that some NBC rings somehow pass intact through the narrow passages of the Lesser Antilles (e.g., Murphy et al 1999;Carton and Chao 1999;Goni and Johns 2003), available in situ observations indicate that the rings themselves are destroyed east of the island arc and only filaments of ring core fluid (e.g., as identified by Lagrangian drifters) are able to enter the eastern Caribbean. We find that NBC rings rarely encounter the Lesser Antilles in a frontal collision.…”

Remote sensing observations of the coherent and non-coherent ring structures in the vicinity of Lesser Antilles

“…However, some numerical simulations (Murphy et al, 1999;Carton and Chao, 1999;Barnier et al, 2001;Garraffo et al, 2003) and previously cited satellite altimeter observations suggest that some NBC rings do somehow pass intact through the narrow passages of the LA. In particular, the results described in Garraffo et al (2003), based on a high-resolution (6 km) Miami isopycnal coordinate model, indicate that as the rings approach the Lesser Antilles, some of them appear to enter the Caribbean nearly intact.…”

Eddy development and motion in the Caribbean Sea

“…These mesoscale eddies and meanders with sizes of 100-500 km travel along the Caribbean Current axis [Fu and Holt, 1983]. Moreover, in the northeastern Caribbean, fluctuations have been noted to be stronger than the mean currents [Molinari et al, 1981] Simulations using the U.S. Navy Layered Ocean Model [Wallcraft, 1991] (a 1/4 ø resolution model with a 5.5-layer reduced gravity and a six-layer model with realistic bottom topography, having an explicit numerical scheme for the reduced gravity, formulated using an Arakawa "C" grid) by Murphy et al [1999] indicated eddy motion penetrated the Lesser Antilles and propagated across the Caribbean in -2 months. Similar eddies can form by horizontal shear instability in two-layer and reduced gravity models [Heburn et al, 1982] and can also be produced when eddies from the North Atlantic Ocean impinge on the Lesser Antilles as in the model of Capella [ 1994].…”