The anatomy of hyperbolic trajectories in the Gulf of Mexico

Abstract

The eastern Gulf of Mexico is an area of strong interaction between eddies (cyclones and anticyclones). The presence of the Loop current and shed Loop Current Eddies intensifies this interaction. Toner et al., (2003, Chlorophyll dispersal by eddy-eddy interactions in the Gulf of Mexico. J. Geophys. Res. Vol. 108(C4), 3105. doi:10.1029/2002JC001499) found that the material curves of the two hyperbolic trajectories (A1 and A2) in the area of this interaction created an advective channel. The channel was verified by using ocean color data, signifying a chlorophyll plume. This study uses all available layers of the Colorado University Princeton Ocean Model (CUPOM), to study (1) the depth to which the hyperbolic structures are present, (2) the vertical structure of these hyperbolic structure and (3) the depth of the advective channel. In the process, we examine both the path of the hyperbolic trajectories in each level and the chaotic nature of these hyperbolic trajectories. ☐ Material curves are initialized in all available layers in order to study the vertical characteristics of the hyperbolic structures. Both hyperbolic structures extend from the surface to the bottom at their respective locations, which for A1 is from the surface to 3000 m while for A2 is from the surface to 125 m. Hyperbolic trajectory A2 follows the bottom topography of the shelf from 50 m to 125 m. The hyperbolic trajectories of A1 follow similar pathways from the surface to 300 m and another similar pattern from 400--3000 m. The hyperbolic structures have chaotic characteristics with particles initialized 1 km to the north, south, east, and west of the structure separating from the structure at a rate .125 f for the upper levels and decreasing to .075 f in the lower levels for A1 where f is the Coriolis parameter. The particles separate at a rate of .05 f for A2. The advective channel of Toner et al. (2003), which was delineated by a chlorophyll plume, is also studied through the water column. It is present only up to 75 meters and is most clearly delineated by the material curves from 30--75 m. The advective channel has an associated volume transport of 1.4 Sverdrups and 2.6 Sverdrups at two different transects.