The Carbonate System in the Yucatan Platform in the Gulf of México

Linda Barranco-Servin, Autonomous University of Baja California UABC, Instituto de Investigaciones Oceanológicas, Ensenada, Mexico, Jose Martin Martin Hernandez-Ayon, Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanologicas, Ensenada, BC, BJ, Mexico, Jorge Herrera-Silveira, Centro de Investigacion y de Estudios Avanzados, Unidad Merida, Merida, Yucatan, YC, Mexico, Daniel Pech, El Colegio de la Frontera Sur, Laboratorio de Biodiversidad Marina y Cambio Climático, Campeche, CP, Mexico, Ismael Marino-Tapia, Center for Research and Advanced Studies, Marine Resources Department, Merida, YC, Mexico and Juan Carlos Herguera, Center for Scientific Research and Higher Education at Ensenada, Ensenada, BJ, Mexico
In this work, the spatial patterns of the variables of the carbonate system [i.e. dissolved inorganic carbon (DIC), total alkalinity (TA), pHtotal and δ13CDIC] in the platform of Yucatan were determined in order to identify the main processes that control its distribution. Data were generated from two campaigns: one in November (2015), representative month of the "nortes" season in winter, and the second in August (2016) representative of the rainy season in summer. CTD cast and discrete samples of seawater were taken at surface and bottom. In general, two oceanographic conditions were observed: 1) Summer sampling was characterized by the presence of Caribbean Surface Water (CSW) advected from the east side of the platform with a temperature >30 °C, salinity of ~36, low values of DIC (2020 μM km-1) and TA (2380 μM km-1), and high pHtotal (~8.3). This water changes as it moves westward, acquiring greater salinity (~36.8), DIC (2120 μM km-1) and TA (2410 μM km-1); therefore, an east-west gradient was observed spatially. The δ13CDIC also reflected this spatial gradient, with more enriched values (~1.24‰) distributed on the east side of the platform. 2) Winter sampling was characterized by submarine groundwater discharge (SDG), which determined both variability and high concentration of DIC (2490 μM km-1), TA (2467 μM km-1), and low pHtotal (~7.5) values, generating a coast-ocean gradient. This was verified with the δ13CDIC that presented values between -4.18 – 0.39‰. The most negative values correspond to the area associated with the coast. This δ13CDIC values, together with the high DIC and TA, and low pHtotal suggest that in the coastal zone, the process of dissolution is taking place due to the effect of SGD.