Dipole-wind interactions under gap wind jet conditions in the Gulf of Tehuantepec, Mexico: A surface drifter and satellite database analysis

Abstract

Gap wind jets (Tehuano winds) trigger supersquirts of colder water and mesoscale asymmetric dipoles in the Gulf of Tehuantepec (GT). However, the effects of successive gap wind jets on dipoles and their effects inside eddies have not yet been studied. Based on the wind fields, geostrophic currents, and surface drifter dispersion, this research documented three dipoles triggered and modified by Tehuano winds. Once a dipole develops, successive gap wind jets strengthen the vortices, and the anticyclonic eddy migrates southwestward while the cyclonic eddy is maintained on the east side of the GT. During the wind relaxation stage, the cyclonic eddy may propagate westward, but due to the subsequent re-intensification of the Tehuano winds, the vortex could break down, as was suggested by surface drifter dispersion pattern and geostrophic field data. The effect of the Tehuano winds was evaluating via eddy-Ekman pumping. Under Tehuano wind conditions, Ekman downwelling (upwelling) inside the anticyclonic (cyclonic) eddies may reach ~ -2.0 (0.5) m d-1 and decrease as the wind weakens. In the absence of Tehuano winds, Ekman downwelling inside the anticyclonic eddy was ~ 0.1 (-0.1) m d-1. The asymmetry of downwelling and upwelling inside eddies during Tehuano wind events may be associated with Tehuano wind forcing.

Petrographic and geochemical analyses of dune sands from southeastern Mexico, Oaxaca, Mexico

“…The occasional longshore currents ultimately raise the Lm concentration in some of the eastern dune sites. Here, the eastward movement of riverine and beach sands was probably derived from anticyclonic eddies (Flores-Vidal et al, 2011;Santiago-García et al, 2019;Trasviña & Barton, 2008;Velázquez-Muñoz et al, 2011).…”

“…Tehuanos are absent during summer, cyclonic eddies have been observed and linked to the westward coastal current. Alongshore, most of the anticyclonic eddies favour coastal tracks flowing eastward (Flores-Vidal, Durazo, Chaverme, & Flament, 2011;Santiago-García, Parés-Sierra, & Transviña, 2019;Trasviña & Barton, 2008) (Figure 3b).…”

Elastic Interaction Between a Mesoscale Eddy‐Pair and an Axisymmetrical Eddy

“…They are also known as eddy‐pairs, vortex pairs or couples, double vortices, modons, or mushroom‐like vortices and have been observed all over the oceans. Some examples include eddy‐pairs of the southern coast of Madagascar (de Ruijter et al., 2004; Ridderinkhof et al., 2013), eastern of Australia (Li et al., 2020), the Norwegian coast (Johannessen et al., 1989), the Mexican coast (Santiago‐García et al., 2019), California coast (Sheres & Kenyon, 1989), in the Alaska current (Ahlnäs et al., 1987), in the South China Sea (Huang et al., 2017) and along the Canary Islands (Barton et al., 2004). These eddy‐pairs are generated by different causes, including the instability of baroclinic currents (Carton, 2001), localized forcing in a viscous stratified fluid (Voropayev & Afanasyev, 1994), or coastal interaction (de Ruijter et al., 2004).…”

The influence of cold filaments on the evolution of dipole structures

“…With the expansion of mesoscale eddy research, mesoscale dipoles have gained increasing attention (McGillicuddy and Robinson, 1997;Machu et al, 1999;Zhao et al, 2021).Dipoles occur in both nearshore regions and the open ocean. Many of the nearshore dipoles are formed by the coastal wind jet (Wang et al, 2006;Zhai and Bower, 2013;Santiago-Garcıá et al, 2019). For example, the formation and maintenance of the summer dipole off of Vietnam is due to the positive and negative wind stress curls on opposite sides of the offshore wind jet, which generate the CE and AE of the dipole, respectively (Wang et al, 2006).…”