Loop Current and Eddy‐Driven Salinity Variability in the Gulf of Mexico

Abstract

The Loop Current System, involving the Loop Current and Loop Current Eddies, is the principal circulation feature in the Gulf of Mexico, which exhibits salinity gradients due to Mississippi River system freshwater discharge and large salinity variability on seasonal timescales. This research uses satellite‐derived sea surface salinity from NASA's Soil Moisture Active Passive and ESA's Soil Moisture and Ocean Salinity missions with altimetric sea surface height data to observe and quantify the redistribution of low‐salinity water by Loop Current System interaction. Freshwater flux in this region during summer months is modulated by Loop Current System configuration as classified by three states. An extended Loop Current transports low‐salinity water southward to the Florida Straits. A Loop Current eddy near the Louisiana‐Texas shelf recirculates low‐salinity water within the central Gulf. During a retracted Loop Current, no interaction occurs and low‐salinity water remains close to the coast in the northern Gulf.

Cell carbon content and biomass assessments of dinoflagellates and diatoms in the oceanic ecosystem of the Southern Gulf of Mexico

“…Spring-summer stratification and winter mixing convection modulate the mixed-layer depth and, consequently, the vertical distribution of the chemical and biological properties [ 24 , 36 ]. Additionally, meteorological and hydrological events such as intense northerly winds in wintertime (e.g., during MF1), and the large freshwater runoff from the Coatzacoalcos river and Grijalva-Usumacinta system during the rainy season (summer-autumn) (e.g., MF2 at Coatzacoalcos), or from the Mississippi river in spring (e.g., MF4 at Perdido) [ 36 – 39 ], are also sources of temporal variability in our morphometric information. All these processes characterize the environmental conditions reflected in our data over the southern basin.…”

Dissolved Inorganic Carbon Transport in the Surface‐Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico

“…Wiseman et al (1997) utilized averaged time series data from 10 years of survey cruises in late July/early August on the Louisiana Shelf and estimated a 15‐day lag of freshwater to a station located halfway between the WLD and BB sectors. Brokaw et al (2019) estimated a K h value of 800 m 2 s −1 in BB sector during August for 2013–2018. If we apply this K h value to our BB study area parameters (Equation ), it yields a residence time of 24 days, which is similar to our current estimates for late spring and early summer.…”

“…A few studies have published horizontal mixing rates for the mid Louisiana Shelf. Brokaw et al (2019) utilized satellite sea surface salinity and sea surface height to quantify low-salinity transport by the Loop Current System in the nGOM and estimated that average August offshore transport in the BB region to reach around 800 m 2 s −1 . Ohlmann and Niiler (2005) used Lagrangian observations to characterize circulation over the nGOM shelf and estimated that the region near the WLD had a mixing rate of 640 m 2 s −1 between October 1993 and October 1994.…”

Do Loop Current Eddies stimulate productivity in the Gulf of Mexico?

“…The GoM open-waters are mostly oligotrophic, as confirmed by more recent bio-optical in-situ measurements from autonomous floats (Green et al, 2014;Pasqueron de Fommervault et al, 2017;Damien et al, 2018). The surface chlorophyll concentration in the GoM open-waters exhibits a clear seasonal cycle which is primarily triggered by the seasonal variation of the mixed layer depth (Müller-Karger et al, 2015) and river discharges (Brokaw et al, 2019). In tandem, the seasonal cycle is strongly modulated by the energetic mesoscale dynamic activity which shapes the distribution of biogeochemical properties (Biggs and Ressler, 2001;Pasqueron de Fommervault et al, 2017).…”