Export pathways for river discharged fresh water in the northern Gulf of Mexico

Abstract

[1] A numerical simulation of the Gulf of Mexico (GoM) using the Navy Coastal Ocean Model (NCOM) is used to identify the pathways by which fresh water discharged by major rivers in the northern Gulf is exported away from the region. The NCOM, a new primitive equation ocean model with a hybrid sigma/geopotential level vertical coordinate, is described along with its application to the GoM region. Trajectories from surface drifters are analyzed to show evidence of the seasonally shifting alongshore and crossshelf transport in the region. The model results are used to determine the preferred locations and times of year for cross-shelf and along-shelf export of low-salinity water from the northern GoM. The annual cycle of local wind stress plays an important role in shifting the export pathway of the fresh water discharged from the major rivers (primarily the Mississippi River) toward the east in the spring/summer, where it can be transported offshore by the currents associated with deep ocean mesoscale eddies, and toward the west in the fall/winter, where it is transported southward along the Mexican coastline as a coastally trapped current.

The stoichiometry of inorganic carbon and nutrient removal in the Mississippi River plume and adjacent continental shelf

“…The concept of varying source terms that differ in stoichiometry was reported by Frigstad et al (2011), who found that the average C / N ratio of suspended particulate organic material (POM) in the Norwegian shelf was the combined result of that due to autotrophs and heterotrophs (the former being higher than Redfield). Differences in uptake by various biological communities may explain observed temporal and spatial differences in stoichiometry (Pahlow and Riebesell, 2000;Li et al, 2000;Li and Peng, 2002). For example, C / N remineralization ratios of 5.48 were reported in the Atlantic Ocean (Li et al, 2000) compared to 4.6 ± 0.6 between latitudes 45-5 • N (Li and Peng, 2002).…”

“…Such strong tidal exchange also introduces Mississippi River-influenced shelf water into this estuary (Li et al, 2011). The dominant coastal current on the Louisiana shelf generally flows to the west, but a clockwise eddy occurs in the Louisiana Bight adjacent to the northwest of the Mississippi River birdfoot delta (Morey et al, 2003;Walker et al, 2005).…”

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

“…These later models generally have better resolutions (with one or two exceptions). Apart from Morey et al [2003] and Zavala-Hidalgo et al [2003b], who used a domain similar to Dietrich and Lin's [994] and hence specify essentially the total Yucatan transport (see below), others' domains include the entire Caribbean Sea. Mooers and Maul's POM (at 20 km resolution and 5 vertical sigma levels; C smag = 0.05) domain is similar to that of Sturges et al [993], including also the Caribbean Sea.…”

Relative dispersion from a high-resolution coastal model of the Adriatic Sea

“…The ocean model used for this study is the NCOM as described in Martin (2000), with some improvements as described in Morey et al (2003) and Barron et al (2006). This is a hydrostatic model, which is similar in its physics and numerics to the Princeton Ocean Model (POM) (Blumberg and Mellor, 1987), but uses an implicit treatment of the free surface and a hybrid vertical grid with sigma coordinates in the upper layers and (optionally) level coordinates below a user-specified depth.…”