Multiple controls on carbon dioxide sequestration in the beagle channel (Southern Patagonia) in early fall

• Published in: Journal of Marine Systems
• Main Authors: Caetano, Ludmila, Guallar, Carles, Martín, Jacobo, Vidal, Montserrat, Cotrim da Cunha, Leticia, Vieira, Rosemary, Amora-Nogueira, Leonardo, Pelegrí, Josep Lluís, Marotta, Roberto
• Other Authors: Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Fundação do Estado do Rio de Janeiro
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: pCO2; High-resolution spatial variability; Patagonia; Sub-Antarctic waters; Beagle Channel; Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10261/296307; https://doi.org/10.1016/j.jmarsys.2023.103858

12 pages, 8 figures, 1 table.-- Data availability: Data will be made available on request Subpolar coastal waters are key hotspots in the global carbon cycle. However, the small-scale distribution of partial pressure of carbon dioxide (pCO2) in these environments and the physical and biological controls underlying this variability are still poorly understood. Here, we examine simultaneous high-resolution spatial measurements of wind speed and pCO2, temperature, salinity, and in-vivo chlorophyll-a fluorescence (chl-a fluo, a proxy of phytoplankton biomass) in surface waters that were obtained during an oceanographic survey in the Argentinian Beagle Channel (subantarctic Atlantic Patagonian) in early fall 2017. The 240 km study transect (centered at 55°S - 67°W) was divided into two zones: (A1) The Beagle Channel innermost portion, semi-enclosed and subject to strong continental influence and (A2) its eastern outlet towards the open Southwest Atlantic. Discrete seawater samples were also collected for apparent oxygen utilization (AOU), nutrients and pH measurements. High-resolution spatial measurements revealed the persistence of pCO2 below atmospheric equilibrium, increasing in median (interquartile range 25–75%) from 314 μatm in the inner Beagle Channel (A1) to 348 μatm towards the adjacent open sea (A2). A decrease in atmospheric CO2 sequestration was associated with an increase in water temperature from 9.5 °C to 10.7 °C, salinity from 30.8 to 32.5, and chl-a fluo from 2.24 to 2.91 mg m−3 along the coastal-offshore gradient. Low AOU and nutrient levels were found in regions inside the channel. Indeed, the relationships between CO2 and temperature or salinity were significantly different from those expected from the theoretical solubility effect, indicating a dominance of metabolic over physicochemical controls on this gas. Moreover, physical factors such as vertical stratification contributed to the variable surface pCO2 values. These findings reveal the existence of short-scale spatial variability of CO2 in ...