Miguel Gilcoto

Computing optimum estuarine residual fluxes with a multiparameter inverse method (OERFIM): Application to the Ria de Vigo (NW Spain)

OERFIM is a two-dimensional (2-D) multiparameter inverse method for calculating estuarine residual fluxes and net ecosystem production rates in estuaries and coastal inlets. OERFIM retains the optimum solution for a weighted system of property conservation equations following the mean squares criterion. The properties involved are volume, salinity, temperature, nutrients (NH4+, NO2−, NO3−2, and PO4−3), dissolved oxygen, and inorganic carbon. Derived variables such as NO, CO, PO, NCO, and PCO are also considered. OERFIM lies between optimum multiparameter analysis and inverse general ocean circulation models. The simplicity of the method allows for derivation of analytical solutions and a clear exposition of the estuarine box models evolution: from the pioneer, just determined Knudsen method to the overdetermined models such as OERFIM. The theoretical analysis also provides a coherent presentation of analytical errors and their relation to the weights entering the equations. We validate the method with field data from the coastal upwelling system of the “Ria de Vigo”, demonstrating that OERFIM results are suitable to understand the solution structure and, therefore, the whole system itself.

Exchange fluxes between the Ría de Vigo and the shelf: A bidirectional flow forced by remote wind

[1] In the Ria de Vigo (western coast of the Iberian Peninsula) the seasonal pattern associated with shelf winds at these latitudes produces upwelling/downwelling episodes that affect the residual circulation. The aim of this paper is to go deeply into the interaction between remote winds and the dynamics of the ria aided by an inverse model. In the Galician r ias the box models (inverse models) have been developed from a two-dimensional (2-D) point of view since the classical baroclinic residual circulation in positive estuaries has a vertical distribution (freshwater outflow through the surface layer and inflow through the bottom layer). However, recent work in the Ria de Vigo has shown the existence of a 3-D residual circulation in the seaward region of the ria. During upwelling (downwelling) conditions a coastal jet enters (leaves) the ria through the northern mouth and leaves (enters) through the southern mouth. The inverse model developed in this paper is a 3-D kinematic box model based on tracer and volume balances with the constraint of nonnegative vertical exchange coefficients. The fluxes obtained confirm, during some periods, the 3-D residual circulation overlying the classical 2-D scheme. It is shown how the 3-D pattern affects the inner ria, causing transversal differences in the flow field. In addition, the model results have been helpful in the discussion of a possible barotropic bidirectional flow associated with remote winds. The results have set the basis for the existence of a bidirectional flow originated by a barotropic interaction with the shelf upwelling.

Short-term variability of fCO2 in seawater and air–sea CO2 fluxes in a coastal upwelling system (Rı́a de Vigo, NW Spain)

Abstract Coastal upwelling systems are regions with highly variable physical processes and very high rates of primary production and very little is known about the effect of these factors on the short-term variations of CO 2 fugacity in seawater ( f CO 2 w ). This paper presents the effect of short-term variability ( 2 fugacity in seawater ( f CO 2 w ), oxygen, temperature and salinity fields in the Ria de Vigo (a coastal upwelling ecosystem). The magnitude of f CO 2 w values is physically and biologically modulated and ranges from 285 μatm in July to 615 μatm in October. There is a sharp gradient in f CO 2 w between the inner and the outer zone of the Ria during almost all the sampling dates, with a landward increase in f CO 2 w . CO 2 fluxes calculated from local wind speed and air–sea f CO 2 differences indicate that the inner zone is a sink for atmospheric CO 2 in December only (−0.30 mmol m −2 day −1 ). The middle zone absorbs CO 2 in December and July (−0.05 and −0.27 mmol·m −2 day −1 , respectively). The oceanic zone only emits CO 2 in October (0.36 mmol·m −2 day −1 ) and absorbs at the highest rate in December (−1.53 mmol·m −2 day −1 ).

From brooding to hatching: new insights from a female Octopus vulgaris in the wild

A brooding Octopus vulgaris female was monitored for 128 days in her natural habitat. The main reproductive events and embryonic development in relation to the temperature inside the spawning den, which was recorded by long-battery-life mini-data loggers, are described in the wild. The den temperature ranged from 12.9 to 19.3°C. The total number of egg strings was 160, and the total number of eggs spawned ranged between 139,040 and 241,760 (mean 190,400). The brooding period, the egg laying interval and the duration of the hatching course lasted 128, 35 and 43 days, respectively. Both egg laying and hatching were intermittent processes. The time taken for embryonic development was variable (85–128 d) and depended on the laying date, temperature and position of the string in the egg cluster and the position of the egg in the egg string. The first hatching observed occurred after a progressive and gradual increase of the temperature from 14.9 to 19.3°C. The 280 min of video recordings taken by scuba divers showed that several times, this female opened and closed a small window in the obstructions of the den entrance to facilitate a way out for the hatchling batches.

Surface water subduction during a downwelling event in a semienclosed bay

The Ria de Vigo is a bay strongly influenced by upwelling-downwelling cycles along the adjacent coast of NW Iberia. Moored and ship-board observations during September 2006 showed that subduction, initially associated with an estuarine circulation, strengthened when a strong downwelling circulation, resulting from northward wind over the coastal ocean, was generated in the outer ria causing ambient waters to be advected outward in the lower layer. Incoming surface waters confined the estuarine circulation to the shallow interior and displaced isopleths downward through the water column at ∼10 m d−1. As the estuarine circulation retreated inward, strong flow convergence developed between middle and inner ria in the layer above 15 m, while divergence developed beneath. The convergence increased through the period of downwelling-favorable wind at a rate consistent with the observed isopleth displacement velocities. The coefficient of turbulent diffusion Kt, from a microstructure profiler, indicated that mixing was strong in the estuarine circulation and subsequently in the downwelling zone, where localized instabilities and temperature-salinity inversions were observed. During the downwelling, concentrations of phytoplankton, including potentially harmful species, increased, especially in the middle and inner ria, as a result of inward advection, subduction and the ability of the dinoflagellates to maintain their position in the water column by swimming. In the course of the 5 day event, the water mass of all but the innermost ria was flushed completely and replaced by waters originating in the coastally-trapped poleward flow along the Atlantic coastline. This article is protected by copyright. All rights reserved.

Rapid response to coastal upwelling in a semienclosed bay

Bays/estuaries forced by local wind show bidirectional exchange flow. When forced by remote Q3 wind, they exhibit unidirectional flow adjustment to coastal sea level. Acoustic Doppler Current Profiler observations over 1 year show that the Ria de Vigo (Iberian Upwelling) responds to coastal wind events with bidirectional exchange flow. The duration of the upwelling and downwelling events, estimated from the current variability, was ~3.3 days and ~2.6 days, respectively. Vectorial correlations reveal a rapid response to upwelling/downwelling, in which currents lag local wind by <6 h and remote wind by <14 h, less than the Ekman spinup (17.8 h). This rapidity arises from the ria’s narrowness (nonrotational local response), equatorward orientation (additive remote and local wind responses), depth greater than the Ekman depth (penetration of shelf circulation into the interior), and vertical stratification (shear reinforcing shelf circulation). Similar rapid responses are expected in other narrow bays where local and remote winds act together and stratification enhances bidirectional flow.

Carbon Data Obtained During the R/V Sarmiento de Gamboa CAIBOX-2009 Cruise in the Atlantic Ocean (25 July - 13 August, 2009)

The item is made of 2 files, of which 1 is the dataset and the other include a small description of the measured variables.-- Dataset contributed to the Project Carbochange

Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Sarmiento de Gamboa Cruise in the North Atlantic Ocean on CLIVAR Repeat Hydrography Section OVIDE-2012 (June 23 - July 20, 2012)

The item is made of 2 files, of which 1 is the dataset and the other include a small description of the measured variables.-- Aida F. Rios ... et al.-- Dataset contributed to the Project Carbochange