On the strength of the California Current: a record from the southern Baja California margin [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): To characterize the strength of the flow of the California Current, we searched in the southern Baja California continental margin, the southernmost site affected by its relatively cool and less saline waters

Particulate organic carbon in the deep-water region of the Gulf of Mexico

Ocean eddies play a major role in lateral and vertical mixing processes of particulate organic carbon (POC), as well as in the transport of heat, salinity, and biogeochemical tracers. In the open waters of the Gulf of Mexico (GoM), however, there are limited observations to characterize how these mesoscale structures affect the spatial distribution of POC in the upper water column, which is important for organic matter cycling and export. We present the distribution patterns of POC relative to mesoscale features throughout the water column in the deep-water region of the GoM during three oceanographic cruises held during the summer months of 2015, 2016, and 2017. Samples were collected under well-stratified upper ocean conditions, which allowed us to assess the spatial and temporal distribution of POC as a function of non-steric sea surface height, density, apparent oxygen utilization, and chlorophyll fluorescence. We further explored the variability of integrated surface layer POC concentrations at stations located within the cores and the edges of cyclonic and anticyclonic eddies, and those collected outside these structures. Although our results indicate mesoscale eddies modulate several important physical and biogeochemical variables and POC concentrations in the upper ocean, these features do not fully explain the spatial distribution of POC concentrations throughout the deep-water region of the GoM. Relatively lower POC concentrations were observed in the border of the cyclonic and the center of the anticyclonic eddies, in contrast to the relatively higher POC concentrations at the center of the cyclonic and the border of anticyclonic eddies. We observed high variability in POC concentration variability outside mesoscale structures, which may be attributed to other processes such as upwelling over the shelves, and the contribution by rivers during the summer especially in the northern and southern GoM

Ocean monitoring, observation network and modelling of the Gulf of Mexico by CIGOM

The tragic accident of the Macondo platform operated by British Petroleum (BP) unleashed in 2010 one of the largest oil spills in history, lasting over three months, spilling nearly 500 million liters of oil in one of the most biodiverse ocean regions. This accident revealed the technological deficiencies for the control of a spill in deep waters of the hydrocarbon industry. Simultaneously it showed important gaps in knowledge to predict the propagation and fate of the large volumes of hydrocarbons at depth and on the surface ocean and, more importantly, on their impact on the great ecosystem of the Gulf of Mexico. The necessity to understand and predict the transport, fate and ecosystem-level impacts of large oil spills in the southern Gulf of Mexico, a key region for oil exploration and extraction, led policymakers, scientists, and industry representatives from PEMEX (the Mexican oil company) to jointly launch an ocean observation project (2015-22) aimed to provide a multi-layered environmental baseline, develop a modern monitoring and computational modeling capacity and promote scientific understanding of the marine environment throughout the Mexican Exclusive Economic Zone (EEZ). The initiative, led by the Research Consortium for the Gulf of Mexico (CIGoM), brought together more than 300 multidisciplinary researchers from more than a two dozen institutions in Mexico and abroad, including the Centre for Scientific Research and Higher Education of Ensenada (CICESE) as the leading institution, the National Autonomous University of Mexico (UNAM), the Centre for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV) in Mérida, the Autonomous University of Baja California (UABC), and the Centre for Engineering and Industrial Development (CIDESI). Financial support was provided by the National Council for Science and Technology and the Ministry of Energy Hydrocarbon Fund

Paleoceanographic evolution of backwater in the Nazca region, Southeastern Pacific, during late Pleistocene

La distribución de conjuntos de radiolarios en los sedimentos superficiales del Pacífico suroriental refleja la advección que la Corriente de Chile efectúa occidentalmente hacia fuera de la costa, así como su mezcla con el Agua Subtropical. Este proceso, ocurre a lo largo de la porción oriental de la Cordillera Nazca (~ 20° S), y es influido por los vientos alisios, rompe la Convergencia Subtropical y deja agua reculada cerca de la costa. Fluctuaciones glacio-interglaciares de esta circulación oceánica, ocurridas durante el Pleistoceno tardío, son reconstruidas mediante conjuntos de radiolarios presentes en el núcleo H96-Tg7. (17°14.04'S, 78°06.16' W). Los episodios glaciares exhiben una circulación oceánica más intensa que los estadios interglaciares. Incursiones extremas del Agua Subtropical hacia el sur ocurrieron durante los Estadios Isotópicos Marinos 11, 5 y 1, sugiriendo que condiciones climáticas extremadamente calientes ocurren episódicamente

Benthic foraminifera and accumulation rates in different time slices of sediment cores from the Equatorial Pacific

Surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep-sea floor. As a rule of thumb, for each 1 mg of organic carbon arriving at the sea floor, one benthic foram shell >150 µm is deposited. The correlation can be used to reconstruct organic flux to the sea floor in the past, and hence the productivity of past oceans. Applying the appropriate equations to box core data from the Ontong Java Plateau in the western equatorial Pacific, we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1.5 and 2.0, with intermediate values for the mid-transition period. Accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period, presumably because increased winnowing removed part of the food supply

Subsidence of the Laguna Salada Basin, northeastern Baja California, Mexico, inferred from Milankovitch climatic changes

La cuenca de Laguna Salada en el norte de Baja California, México, es un semigraben activo producto de la tectónica transtensional del Golfo de California. Esta cuenca endorréica es sensible a cambios en sedimentación por variaciones en el aporte de sedimentos de fuentes cercanas y distales transportados por arroyos de las sierras adyacentes y por el Río Colorado. Esta cuenca es un sitio excepcional para explorar el uso de cambios climáticos cíclicos como herramienta de datación y estimar tasas de sedimentación y subsidencia en el área. Para demostrar esto se presenta un análisis de series de tiempo de un registro de rayos de gama de un pozo geotérmico exploratorio perforado adyacente a la falla de Laguna Salada, la cual limita el margen oriental de la cuenca. Los resultados del análisis indican que el espectro de los primeros 980 m del registro de rayos gama tiene una alta coherencia con el espectro de registros isotópicos paleoclimáticos de ä18O del Pleistoceno, los cuales exhiben fuerte periodicidad de Milankovitch. Con base en esto, es posible correlacionar estadios climáticos con paquetes sedimentarios cortados por el pozo. De esta manera es posible constreñir las edades de los sedimentos depositados durante los últimos 780 kiloaños con una incertidumbre estimada en 10 ka. También se deriva un modelo sencillo de conversión de profundidad a tiempo para la cuenca de Laguna Salada. El modelo indica que la tasa de sedimentación para los últimos 780 ka ha permanecido constante con un valor de ~1.6 mm/año. Dada la proximidad del sito de perforación a la falla de Laguna Salada, tomamos este valor como la tasa de subsidencia de esta falla

Carbonate sedimentation and stable isotope ratios of sediments from the western equatorial Pacific

Deep-sea records of the Pacific Ocean show dramatic variations in the dissolution intensity of calcium carbonate through the late Pleistocene. Extremes are characterized by much depressed dissolution intensity during deglaciation (preservation spikes) and much enhanced dissolution intensity during ice growth (dissolution spikes). Increased dissolution intensity at dissolution spikes distorts delta18O records by preferential removal of 16O-rich shells, resulting in heavier delta18O values at these sections. The delta18O values tend to remain unaltered at deglacial preservation spikes. Thus the fluctuations of carbonate dissolution intensity modify the late Pleistocene oxygen isotope records in such a fashion that apparent 'climate optima' (as defined by the lightest delta18O values) tend to shift toward preservation spikes, while apparent 'glacial maxima' (characterized by the heaviest delta18O values) shift toward dissolution spikes