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Redalyc.Tidal Current Components in the Southern Bay of Campeche Geofísica Internacional ISSN: 0016-7169 [email protected] Universidad Nacional Autónoma de México México Salas de León, David A.; Monreal-Gómez, María A.; Salas-Monreal, David; Expósito-Díaz, Gilberto; Riverón-Enzastiga, Mayra Lorena; Vázquez-Gutiérrez, Felipe Tidal Current Components in the Southern Bay of Campeche, Gulf of Mexico Geofísica Internacional, vol. 46, núm. 2, april-june, 2007, pp. 141-147 Universidad Nacional Autónoma de México Distrito Federal, México Disponible en: http://www.redalyc.org/articulo.oa?id=56846204 Cómo citar el artículo Número completo Sistema de Información Científica Más información del artículo Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Página de la revista en redalyc.org Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto Geofísica Internacional (2007), Vol. 46, Num. 2, pp. 141-147 Tidal Current Components in the Southern Bay of Campeche, Gulf of Mexico David A. Salas-de-León1, María A. Monreal-Gómez1, David Salas-Monreal2, Gilberto Expósito-Díaz1, Mayra L. Riverón-Enzastiga1 and Felipe Vázquez-Gutiérrez1 1 Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mexico City, Mexico 2 Centro de Ecología y Pesquerías, Universidad Veracruzana, Veracruz Mexico Received: March 17, 2006 ; accepted: May 17, 2007 Resumen Datos sobre la magnitud y dirección de las corrientes fueron obtenidos en la Bahía de Campeche, al sur del Golfo de México, de marzo a mayo de 1997, para obtener las principales componentes de marea en la región. Las elipses y fases de las diferentes componentes de marea fueron obtenidas mediante un ajuste por mínimos cuadrados acoplado con una modulación nodal a partir de las series horarias de corrientes por marea. Los constituyentes P1 y K2 se infi rieron a partir de los constituyentes K1 y S2, respectivamente. Los resultados muestran la dominancia del armónico K1 en la plataforma continental al sur de la Bahía de Campeche, una región de mareas mixtas con dominancia semidiurna en la zona del umbral de Cayo Arcas y una región de transición entre Cayo Arcas y las estaciones al oeste en la zona de estudio. Las diferencias en las amplitudes de las corrientes de marea en la vertical fueron despreciables, mientras que las diferencias en las fases muestran un retraso signifi cativo entre la superfi cie y el fondo. El sentido de rotación de las elipses de marea en Cayo Arcas es negativo, mientras que en las otras estaciones fue positivo. Cayo Arcas tiene una fuerte infl uencia en las corrientes de marea ya que su fase y sentido de rotación varían. Palabras clave: Corrientes de marea, armónicos de marea, Bahía de Campeche, Golfo de México Abstract Current velocity data in the Southern Bay of Campeche, Gulf of Mexico, were obtained from March 1997 to May 1997, in order to compute tidal ellipses and phase lags in the region. Tidal ellipses and phase lags were calculated via a least squares fi t method coupled with nodal modulation from the hourly time series. Constituents P1 and K2 were inferred from K1 and S2, respectively. The K1 component is dominant in the southern shelf of the Bay of Campeche, a region of mixed tides with semidiurnal dominance at the Arcas Kay sill, and a transition region between Arcas Kay and the southern-western stations. Vertical differences in tidal current amplitudes were negligible. There was a signifi cant phase lag from surface to bottom. The sense of rotation for the tidal ellipses near Arcas Kay was negative, while at other stations it was positive. Arcas Kay has a strong infl uence on tidal currents because of vertical phase and sense of rotation variation with depth. Key words: Tidal currents, tidal harmonics, Bay of Campeche, Gulf of Mexico. Introduction Yucatan peninsula (Salas-de-León, 1986; Salas-de-León and Monreal-Gómez, 1997). Near the port of Campeche Hydrodynamics of coastal ocean waters features tides are mixed, with diurnal dominance (Salas-de-León, a variety of processes, including the tides. The Bay of 1986). In the southwestern part of the bay, tides are Campeche (Figure 1) is a region of major economical ac- diurnal as shown by the form number (Salas-de-León and tivities such as petroleum production and fi sheries. Monreal-Gómez, 1998). However, the coastal circulation in the Bay of Currents in the Bay of Campeche follow the Campeche is not fully understood. bathymetry. The M2 tidal component from the southern Gulf of Mexico enters by the Yucatan Channel turns Typical water depths are less than 200 m. Beyond the westward at the amphidromic point near Progreso, and shelf edge, depths increase rapidly to values over 1000 fl ows toward the Bay of Campeche by Arcas Key (Figure m, and reach more than 3000 m at the centre of the bay. 2). Low amplitudes were observed near Coatzacoalcos The tides in the region are diurnal (Grace, 1932) with while, the highest tides were found at Arcas Key and an amphidromic point for M2 (Figure 2) off the western near Isla Del Carmen. The obtained magnitude and 141 Fig. 1. Bay of Campeche, with mooring positions of current-meters. Depth contours in meters. direction of tidal currents for the points corresponding to Table 1 the anchorages (Salas-de-León, 1986), were as follows: C1, 0.41 cm s-1 and 101°; C2, 0.32 cm s-1 and 122°; C3, Location, geographical position and depth of current 0.09 cm s-1 and 125°; and C4, 0.04 cm s-1 and 147°. There meter stations is no further information on tidal currents in the Bay of Campeche. Station Latitude Longitude Total depth number (N) (W) (m) In this study we present a tidal current analysis for the region. Results on sub-inertial frequencies will be published separately. Our data were collected over a three 1 20° 08.035’ 92° 02.601’ 77.0 month period, and include coastal circulation relative 2 19° 26.762’ 92° 08.957’ 51.3 to tides, wind data, atmospheric pressure and non-local 3 18° 37.199’ 93° 12.337’ 28.0 forcing. Results from this study are expected to improve 4 18° 32.868’ 94° 01.216’ 75.5 coastal management procedures for the region and provide information for emergency situations in case of oil spills. Two or three current meters were moored at different Methods depths (Table 2). Sampling interval was 20 minutes. Hourly time series were fi ltered with a Godin-type low-pass fi lter A2 A (Emery and Thompson, 1998). A total of ten RCM4 and RCM7 Aanderaa current 4 5 -4 -1 meters were deployed from March 1997 to May 1997 at Frequencies higher than 1.38 × 10 s , equivalent to a 2 h four mooring sites (Figure 1 and Table 1). The current period, were removed. The fi lter does not produce phase meters record velocity, temperature, conductivity, and lags (Salas-Monreal, 2006). water pressure; temperature, conductivity, and water pressure data were not used in this analysis. The positions Tidal ellipse parameters and Greenwich phase lags of the moored current meters were obtained from the GPS were calculated via a least squares fi t coupled with navigation system aboard the R/V “Justo Sierra” of the nodal modulations. This analysis was carried out only Universidad Nacional Autónoma de México (Table 1). for constituents that could be resolved over the length Calibration of the instruments and data quality analysis of the record (e.g., Godin, 1972; Godin, 1976; Foreman, were performed by V. G. Koutitonsky at the University of 1996). Constituent P1 and K2 were inferred from K1 and Québec, in Rimouski, Canada. S2, respectively. 142 Table 2 Instrument type, stations, sampling depth, start and end recording times. The year was 1997, and the time is in GMT (- 6 h). C, current meter, station numbers are as in Figure 1. S, M, and B is surface, mid water and bottom. Instrument on the mooring line Sampling Depth (m) Start GMT Time End GMT Time (identifi cation name) RCM7 (C1S) 36.5 22:40/06/03 11:20/22/05 RCM4 (C1B) 70.5 22:40/06/03 15:20/27/04 RCM7 (C2S) 23.0 16:20/06/03 19:00/21/05 RCM4 – S (C2M) 34.5 16:20/06/03 19:00/21/05 RCM4 (C2B) 44.5 16:20/06/03 19:00/21/05 RCM4 – S (C3S) 16.0 17:40/03/03 19:00/12/06 RCM4 – S (C3B) 23.5 17:40/03/03 19:00/12/06 RCM4 – S (C4S) 17.3 17:40/02/03 12:00/20/05 RCM4 – S (C4M) 47.5 17:40/02/03 12:00/20/05 RCM4 (C4B) 66.0 17:40/02/03 12:00/20/05 Fig. 2. M2 cotidal lines. Amplitude (dashed, in cm) and phase (solid, GMT, in degrees). After Salas-de-León and Monreal-Gómez (1997). Results and discussion Tidal constituent K1 was dominant for nearly all surface tidal currents, down to mid water depths. Main tidal current constituents were calculated for However, at station 4 the main constituent of the surface tidal current was OO . Near the bottom, the dominant each station and depth (Tables 3 to 6). Major (a+ + a-) 1 constituent varied from one position to another. At station and minor (a+ - a-) ellipses, angles of inclination (θ) with 1 the dominant component was O2, while at station 3 it positive x axis (Figure 3), phases (g) relative to Greenwich was 2Q and at station 4 the Q constituent. and constant phase angles (g+ and g-) for each constituent 1 1 were reported as in Godin (1972). Unfortunately, current The period of oscillation of tidal currents was meter C2B proved to be unusable.
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