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Las condiciones oceanográficas del océano Pacífico nororiental frente a Baja California (México) se estudian sistemáticamente mediante el programa Investigaciones Mexicanas de la Corriente de California (IMECOCAL), que es una extensión hacia el sur del programa California Cooperative Fisheries Investigations (CalCOFI). La síntesis de la información a largo plazo obtenida de estos programas Oceanographic conditions over the continental shelf off Magdalena Bay (Mexico) in 2011-2012 Condiciones oceanográficas en la plataforma continental frente a bahía Magdalena (México) en 2011-2012

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C M INTRODUCTION The Magdalena-Almejas Bay coastal lagoon system consists of three bodies of water: Almejas Bay (AB), Magdalena Bay (MB), and the channel zone (CZ). They are interconnected by two channels, known as the Gaviotas Channel and the San Carlos Channel (fig. 1a). The AB inlet is INTRODUCCIÓN El sistema lagunar de Bahía Magdalena-Bahía Almejas está morfológicamente compuesto por tres cuerpos de agua: Bahía Almejas (BA), Bahía Magdalena (BM) y zona de canales (ZC). Los tres cuerpos de agua se interconectan mediante dos canales interiores, referidos como Canal San Seasonal variations of the thermohaline structure in the Magdalena-Almejas Bay lagoon system and adjacent sea Variaciones estacionales de la estructura termohalina en el sistema lagunar de Bahía Magdalena-Bahía Almejas y el mar adyacente

The major (M w 8.2) intraplate normal-fault earthquake of 8 September 2017 in the Gulf of Tehuantepec (Chiapas, Mexico) generated a strong tsunami that severely impacted the nearby coasts of Mexico and Central America. Tsunami waves in the near-field area were measured by seventeen high-resolution coastal tide gauges and by three open-ocean DART stations anchored offshore from the affected region. Data from these sites, together with those from four distant DARTs, were used for comprehensive analyses of the 2017 event. De-tided sea level time series were examined to determine the statistical and spectral characteristics of the 2017 tsunami waves along the Mexican and Central American coastline. The characteristics of the recorded waves from this near-field event were compared with those from two great far-field events: the 2010 Chile and the 2011 Tohoku tsunamis. Maximum trough-to-crest wave heights for the 2017 tsunami were recorded at Puerto Chiapas (351 cm), Salina Cruz (209 cm), Acapulco (160 cm), Huatulco (137 cm) and Acajutla, El Salvador (118 cm). While maximum 2010 and 2011 tsunami waves were observed at specific ''hot spots'' (sites with a high Q-factor and pronounced resonant properties, such as Manzanillo and Acapulco), the ''strengths'' of the recorded 2017 tsunami waves were mostly determined by distance from the source. Contrary to the maximum wave heights, the general spectral properties of the tsunami signals for all three events were highly similar at a given coastal site and mainly resemble the spectral structure of background oscillations at the same site. This similarity indicates that the frequency properties of the tsunami waveforms for a steadystate tsunami signal are mainly determined by local topographic features rather than by the source parameters. Estimates of the ''colour'' of an event (i.e., the open-ocean tsunami frequency content) show that the 2017 Chiapas tsunami was mostly ''reddish'' (long-period), with 68% (DART 43413) to 87% (DART 43412) of the total tsunami energy related to waves with periods [ 35 min. In contrast, the 2010 and 2011 tsunamis were ''reddish-blue'', with 48-57% associated with long-period waves ([ 35 min) and 52-43% with short-period waves (2-35 min). The dominant periods of the tsunami waves were mostly linked to the shape, length, and width of the source region: the larger the source and the shallower its depth, the longer the periods of the generated tsunami waves. The complicated structure of the source explains the saturated and wide frequency-band character of the tsunami spectra. Our analysis also reveals an anisotropic nature to the 2017 tsunami waves; waves that propagated northeastward along the mainland coast of North America and southeastward along the Central American coast were significantly different from those that propagated southwestward, normal to the source orientation. This aspect of the wave field appears to be related to two distinct types of waves; ''trapped (edge) waves'' retained on the shelf (which plays the role of a ''wave guide''...