Mississippi River water in the Florida Straits and in the Gulf Stream off Georgia in summer 2004

Abstract

A coherent plume from the Mississippi River was detected in MODIS imagery in July–October 2004 extending from the eastern Gulf of Mexico into the Florida Straits (FS), and reaching the Gulf Stream (GS) off Georgia. The plume was sampled from ships in the FS and the GS. In early August, the plume was about 10–20 km wide in the western FS and about 50 km wide off Georgia. The FS ship survey (16–26 August) documented a 50 km, 10–20 m deep band with anomalies in surface salinity (−0.8), temperature (0.5°C), and surface chlorophyll concentration (2×) relative to FS waters outside the plume. Nutrient concentrations were only slightly higher in the FS plume and there was no apparent increase in colored dissolved organic matter. We estimate that the plume carried some 23% (∼2778 m3 s−1) of the Mississippi River discharge between July and September 2004 into the GS.

Mississippi waters reaching South Florida reefs under no flood conditions: synthesis of observing and modeling system findings

“…The LC is a branch of the North Atlantic western boundary current, which later forms the Gulf Stream. Episodes of such LC entrainment were documented in the past and were associated with the presence of MR waters as far as the Florida Keys area, or even further downstream the Gulf Stream along the southeastern USA (Ortner et al 1995;Gilbert et al 1996;Hu et al 2005;Schiller and Kourafalou 2014). The LC can thus provide nutrients to the Florida Keys, which host the largest coral reefs in the continental USA, and as such, it is a vector of connectivity between the Mississippi Delta area and South Florida ecosystems.…”

“…The Mississippi River (MR) is the largest river in North America, with an average discharge of~13,500 m 3 s −1 (Hu et al 2005). The MR is a major source of freshwater, but also of nitrates and organic matter for the Gulf of Mexico (GoM).…”

The ecosystem baseline for particle flux in the Northern Gulf of Mexico

“…The transport of Mississippi River water within the Gulf of Mexico is highly variable, spatially and temporally, and depends strongly on winds, mesoscale eddies and the loop current system (Schiller et al, 2011;Schiller and Kourafalou, 2014). Based on satellite images, the influence of Mississippi waters can be observed as far away as the Florida Straight (Hu et al, 2005). The freshwater intrusions of the Mississippi can often be detected by an increase in surface chlorophyll concentrations (Hu et al, 2005;Schiller et al, 2011;Schiller and Kourafalou, 2014).…”

“…Based on satellite images, the influence of Mississippi waters can be observed as far away as the Florida Straight (Hu et al, 2005). The freshwater intrusions of the Mississippi can often be detected by an increase in surface chlorophyll concentrations (Hu et al, 2005;Schiller et al, 2011;Schiller and Kourafalou, 2014). Moreover, the influence of Mississippi-derived sediment is clearly visible in the distribution of CaCO 3 in seafloor sediments, where a 'tongue' with low-CaCO 3 sediments (< 10% CaCO 3 of sediment DW) extends from the mouth of the Mississippi River towards the Southeast (Balsam and Beeson, 2003;Ellwood et al, 2006).…”

“…The Mississippi also carries large amounts of fine, suspended sediment, which settles near the Mississippi Delta and dominates the seafloor sediment there (Balsam and Beeson, 2003;Ellwood et al, 2006). This eutrophic river plume is advected by the strong currents in the Gulf of Mexico depending on the wind conditions and the position of the loop current (Walker, 1996;Walker et al, 2005;Schiller et al, 2011), and can at times be detected as far south as the Florida Straight (Hu et al, 2005;Schiller and Kourafalou, 2014). The complex interaction between different waters (with differing nutrient and trophic states) and highly variable currents leads to a very heterogeneous and dynamic system.…”