Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012

Abstract

Abstract. Coastal upwellings along the eastern margins of major ocean basins represent regions of large ecological and economic importance due to the high biological productivity. The role of these regions for the global carbon cycle makes them essential in addressing climate change. The physical forcing of upwelling processes that favor production in these areas are already being affected by global warming, which will modify the intensity of upwelling and, consequently, the carbon dioxide cycle. Here, we present monthly high-resolution surface experimental data for temperature and partial pressure of carbon dioxide in one of the four most important upwelling regions of the planet, the Mauritanian-Cap Vert upwelling region, from 2005 to 2012. This data set provides direct evidence of seasonal and interannual changes in the physical and biochemical processes. Specifically, we show an upwelling intensification and an increase of 0.6 Tg yr −1 in CO 2 outgassing due to increased wind speed, despite increased primary productivity. This increase in CO 2 outgassing together with the observed decrease in sea surface temperature at the location of the Mauritanian Cap Blanc, 21 • N, produced a pH rate decrease of −0.003 ± 0.001 yr −1 .

<i>p</i>CO<sub>2</sub> variability in the surface waters of the eastern Gulf of Cádiz (SW Iberian Peninsula)

“…The Gulf of Cádiz acts as a source of CO 2 to the atmosphere during the months of summer (ST2, ST6) and autumn (ST3, ST7) and as a sink in spring (ST1, ST5) and winter (ST4, ST8). Previous studies conducted in the Gulf of Cádiz are consistent with the behaviour found in this study (González-Dávila et al, 2003;Aït-Ameur and Goyet, 2006;Ribas-Ribas et al, 2011).…”

“…With the total surface of the study area (52.8 × 10 2 km 2 ) and the mean annual flux during the eight cruises, the uptake capacity estimated for the Gulf of Cádiz will be 4.1 Gg C yr −1 . The findings of previous studies carried out in the Gulf of Cádiz coincide with the behaviour observed in this study (Santana-Casiano et al, 2002;González-Dávila et al, 2003;Huertas et al, 2006;de la Paz et al, 2009;Ribas-Ribas et al, 2011), with the exception of the study by Aït-Ameur and Goyet (2006) in which it was estimated that the Gulf of Cádiz acts as a source of CO 2 to the atmosphere, although that study only corresponds to the summer season.…”

“…the Guadalquivir, Rio Tinto, Odiel and Guadiana. Various studies have been conducted in this area to evaluate the variability in the sea surface partial pressure of CO 2 (pCO 2 ), although they cover smaller areas and a shorter duration of time than this work (González-Dávila et al, 2003;Aït-Ameur and Goyet, 2006;Huertas et al, 2006;Ribas-Ribas et al, 2011) or only a specific area like the Strait of Gibraltar (Dafner et al, 2001;Santana-Casiano et al, 2002;de la Paz et al, 2009). All of these studies, however, have determined that this zone behaves as a sink of CO 2 with seasonal variations induced mainly by the combination of the fluctuations of biomass concentration and temperature.…”

Factors controlling pCO<sub>2</sub> variability in the eastern Gulf of Cádiz (SW Iberian Península)

“…This input of colder waters, with greater loading of nutrients and higher concentrations of CO2 (e.g. Liu et al, 2010;Xue et al, 2015;González-Dávila et al, 2017) can affect the distributions of pCO2 found in the Gulf of Cádiz.…”

A Surface Ocean CO2 Reference Network, SOCONET and Associated Marine Boundary Layer CO2 Measurements

“…Unattended measurements referenced against compressed air standards traceable to atmospheric CO 2 standards are now done routinely on ships and, since the 2000s, on moorings (Sutton et al, 2014). The measurements cover much of the global ocean, and allow regular access to regions of economic and environmental importance such as upwelling regions (González-Dávila et al, 2017). Many of the measurements are performed following standard operating procedures (e.g., Pierrot et al, 2009) and much of the data are submitted to global datasets and undergo independent secondary quality control.…”