Abstract
Abstract. The dynamics of the Loop Current (LC) and the detached Loop Current eddies (LCEs) dominate the surface circulation of the Gulf of Mexico (GoM) and transport Caribbean Water (CW) into the gulf. In this work, 25 years (1993–2017) of daily satellite data are used to investigate the variability of these physical processes and their effect on chlorophyll a (Chl a) concentrations from 1998 to 2017, including temporal changes, mean differences, and regional concentration tendencies. The physical variables analyzed are absolute dynamic topography (ADT) and oceanic currents. From the ADT and oceanic current monthly climatologies, it is shown that there is an annual intrusion of CW with an inward incursion that starts in spring, peaks in the summer, reaches to 28∘ N and 90.45∘ W, and then retreats in winter to approximately 26.5 ∘ N and 88.3 ∘ W. Minimum surface Chl a concentrations (< 0.08 mg m−3) are found during the summer–autumn period inside the region of maximum incursion of CW; the opposite is observed during the winter period when Chl a concentrations were at a maximum, e.g., > 0.14 mg m−3. The 3-year running averages of the ADT 40 cm isoline qualitatively reproduce the climatological pattern of 25 years showing that before 2002 CW was less intrusive. This suggests that from 2003 onward, larger volumes of oligotrophic waters from the Caribbean Sea have invaded the western GoM and reduced mean surface Chl a concentrations. A direct comparison between the 1998–2002 and 2009–2014 periods indicates that in the latter time interval, the Chl a concentration above waters deeper than 250 m has decreased significantly.
Highlights
The effects of global warming on the circulation of the world’s oceans and its concomitant consequences on the oceans’ biological productivity are some of the most important scientific and economic issues of our times
The Loop Current (LC) enters the gulf through the Yucatán Channel and exits through the Straits of Florida, penetrating northward into the Gulf of Mexico (GoM) until instabilities form in the current and a ring-like LC eddies (LCEs) pinches off
In 2005, Leben, using the 17 cm contour in daily sea surface topography maps, tracked the LC thermal fronts in the sea surface temperature images during good thermal contrast
Summary
The effects of global warming on the circulation of the world’s oceans and its concomitant consequences on the oceans’ biological productivity are some of the most important scientific and economic issues of our times. Interacting seasonal and stochastic processes could trigger the separation of the LCEs (Fratantoni et al, 1998; ZavalaHidalgo et al, 2003, 2006) as well as forming Caribbean eddies and other topographic features (Garcia-Jove et al, 2016) In this context, the LC system has some similarities with the North Brazil Current retroflection (Pichevin et al, 1999; Goni and Johns, 2001; Zharkov and Nof, 2010), the Agulhas retroflection (de Ruijter et al, 1999; Baker-Yeboah et al, 2010), and the Gulf Stream, wherein large meanders pinch off as warm rings (Brown et al, 1983; Richardson, 1983; Savidge and Bane, 1999).
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