Short‐timescale thermohaline variability and residual circulation in the central segment of the coastal upwelling system of the Ría de Vigo (northwest Spain) during four contrasting periods

Abstract

[1] Sixteen hydrographic surveys were carried out in the middle segment of the Ría de Vigo (northwest Spain) at 3-to 4-day intervals during February, April, July, and September 2002 (four surveys per period). Simultaneously, an acoustic Doppler current profiler (ADCP) mooring recorded the velocity profile. Combination of direct current measurements with the output of an inverse model based on the time course of the distributions of salinity and temperature allowed an objective analysis of the effect of the meteorological forces on the hydrodynamics of the Ría. Remote shelf winds explained more than 65% of the variability of the subtidal circulation, which responded immediately to this forcing (lag time, <2 days). Shelf winds created a simple two-layered circulation pattern, with a surface outgoing current under northerly winds and a surface ingoing current under southerly winds. A three-layered circulation developed during the transitions from northerly to southerly winds and vice versa. At the same time, an empirical orthogonal function (EOF) analysis demonstrated the lack of contribution of local winds to the subtidal dynamics of the ría. Continental runoff and heat exchange with the atmosphere explained less than 5% and 25% of the variability observed in the subtidal circulation of the Ría de Vigo.Citation: Piedracoba, S., X. A. Á lvarez-Salgado, G. Rosón, and J. L. Herrera (2005), Short-timescale thermohaline variability and residual circulation in the central segment of the coastal upwelling system of the Ría de Vigo (northwest Spain) during four contrasting periods,

Net ecosystem metabolism of a coastal embayment fertilised by upwelling and continental runoff

“…The effect of coastal winds is specially relevant in areas affected by permanent or seasonal upwelling, as it is the case of the Galician rías (Rosón et al, 1997;Álvarez-Salgado et al, 2000;Pardo et al, 2001), the Chilean fjords (Aysen Fjord, Cáceres et al, 2002) or Bantry Bay in South West Ireland (Edwards et al, 1996). Similarly high percentages of the subtidal current variability explained by coastal winds have been found in the Ría de Vigo (>65%; Piedracoba et al, 2005), the Ría de Arousa (50%; Rosón et al, 1997) (Rosón et al, 1997;Álvarez-Salgado et al, 2000). Since the volumes of these rías up to the segment where the flows were calculated are also around 0.50 Km 3 , the corresponding flushing times results to be 8 days (renewal rate of 12% d -1 ).…”

“…Furthermore, upwelling-favourable winds blow intermittently during the summer, producing a succession of short-living upwelling episodes separated by intervals of stratification or weak downwelling Pardo et al, 2001;Piedracoba et al 2005). This is a pattern typical of coastal upwelling systems at temperate latitudes (Hill et al, 1998).…”

“…A better agreement (r 2 = 0.97, p < 0.001) was found between measured currents and computed flows in the middle Ría de Vigo by Piedracoba et al (2005). It should be noted that in the ADCP current meter was deployed at 40 m depth in the study of the Carter et al, 1979;Walters and Gartner, 1985;Valle Levinson et al, 1998;Wong and Moses-Hall, 1998;Wong and DiLorenzo, 1988;Wong, 2002).…”

Role of across‐shelf currents in the dynamics of harmful dinoflagellate blooms in the northwestern Iberian upwelling

“…During winter, the coastal circulation is dominated by the presence of the Iberian Poleward Current (IPC) on the shelf (Frouin et al 1990;Peliz et al 2005); this current is a northward surface stream that also induces a shoreward flow and, hence, causes downwelling near the coast (Á lvarez-Salgado et al 2003). Across-shelf transport imposed by coastal upwelling and downwelling is extremely intensified in the Rías Baixas (Figueiras et al 2002;Piedracoba et al 2005) because of their almost perpendicular orientation to the main coastline. Thus, during upwelling, the circulation of the Rías Baixas consists of a surface outflow that is compensated by the inflow of coastal upwelling water at the bottom.…”

Anatomical differences among Atlantic and Mediterranean populations of Trisopterus luscus (Pisces)

“…Further research is needed to identify possible environmental factors involved. (Álvarez-Salgado et al 2000, Piedracoba et al 2005.…”