Anticyclonic‐cyclonic eddies and their impact on near‐surface chlorophyll stocks and oxygen supersaturation over the Campeche Canyon, Gulf of Mexico

Abstract

Physical and biological data were gathered over the Campeche Canyon area, Gulf of Mexico, in summer 1999. These include hydrographical and meteorological parameters, and oxygen content, as well as, at some oceanographic stations, suspended particulate matter (SPM), chlorophyll‐a, and in vivo natural fluorescence profiles. Dry air from the east set up a latent heat flux that ranged from 50 to 300 Wm−2. The wind mixed layer (ML) was isothermal and averaged 40 m thick, but with a noticeable increase of oxygen supersaturation toward the northwest. Temperature and dynamic height structure reveal an anticyclone‐cyclone eddy pair. At the southeastern part of the study area a noticeable thermal gradient was observed toward the shelf break of the Campeche Bank, which corresponded to a tilting up (doming) of low oxygen saturation midwater to near the base of the ML. This doming of isotherms along the margin of the Campeche escarpment is likely an upper‐ocean response to the sharp gradient in water depth between the canyon and outer continental shelf. It is suggested that the doming of midwater on to the Campeche escarpment and at the head of the Canyon, as denoted by locally low values of oxygen saturation, plays an important role in the biological patterns. Throughout the field area, the values of total SPM were higher than reported previously for subtropical open ocean environments. The impact of autotrophic‐heterotrophic biogeochemical processes on chlorophyll was reflected in the local deepening of the deep of chlorophyll maximum (DCM) and the depth of the euphotic zone within the anticyclonic eddy.

Bio-optical characterization of the waters of the Bay of La Paz, southern Gulf of California, during late spring 2004

“…Since k-values varies according to the wavelengths of light, values ranging from 0.035 to 0.140 m -1 have been reported by Lalli & Parsons (2006), in agreement with our observations. Similar observations were reported by Salas de León et al (2004) who found mean values of k of 0.05 for waters of the southern Gulf of Mexico. According to Falwowski & Raven (2007), values of k could be potentially affected by the amount of chlorophyll contained in living phytoplankton and in plant debris or the dissolved and particulate matter along water column.…”

Continuously stratified flow dynamics over a hollow

“…The velocity patches of the instantaneous velocities (contours of −45 cm s −1 in Figures 6a and 6c) on the leeward side of the hollow could have represented internal motions [ Benjamin and Seaman , 1985; Armi , 1986; Davis , 1997]. These motions could have been produced by the interaction between the increasing bottom slope and the stratified flow [ Salas‐de‐León et al , 2004] but were not resolved appropriately by the sampling. The development of lee waves was better suggested by data from the anchored ADCP station.…”

Modeling environmental influence on Atlantic bluefin tuna bycatch by Mexican longliners in the Gulf of Mexico

“…The continental shelf extension is variable, which is very narrow off the coasts of TM and VR, progressively widening by the Yucatan Peninsula. Among the most important physiographic features of the GoM is the Campeche canyon that strongly influences oceanographic dynamics on a regional scale through the formation of eddies and upwelling events (Escobar‐Briones, Estrada‐Santillán, & Legendre, ; Salas‐de León, Monreal‐Gómez, Signoret, & Aldeco, ). The GoM oceanographic characteristics are largely determined by the presence of the Loop Current (Figure ), which is the dominant feature of the circulation in the eastern part of the GoM and shows great seasonal and annual variability in trajectory and intensity (Aguirre, ; Monreal‐Gómez, Salas de León, & Gracia‐Gasca, ; Monreal‐Gómez, Salas de León, & Velasco‐Mendoza, ; Zavala‐Hidalgo, Morey, & O'Brien, ).…”