The southwestern South Atlantic continental shelf biogeochemical divide

Physical and biological effects on the carbonate system during summer in the Northern Argentine Continental Shelf (Southwestern Atlantic)

“…The likely strong CO 2 uptake and the fCO 2 sw spatial variability found here over the different systems along the COSTAL-AR section in summer are in agreement with what was found previously at the Northern Argentine Continental Shelf (Bianchi et al, 2009;Kahl et al, 2017;Kahl, 2018;de Oliveira Carvalho et al, 2022). Nevertheless, some differences in the values of the carbonate system found between our results and previous observations may be due to the predominant processes occurring at the time of sampling.…”

“…Hence, better understanding the role that individual continental shelves play in the global carbon budget, and associated acidification problem, becomes presently more relevant in a context of global change (Pörtner et al, 2022). The area of the present study lies within the transitional zone between the two biogeochemical regions defined by de Oliveira Carvalho et al (2022). In this context, we focused the discussion on the possible physical and/or chemical-biological processes affecting the carbonate system distribution in the top 50 m along the COSTAL-AR section.…”

“…Overall, the Southwestern Atlantic Ocean acts as a sink of atmospheric CO 2 south of 30˚S (0.3-0.6 Pg C yr -1 according to Takahashi et al, 2002), and is close to equilibrium with the atmospheric CO 2 to the north. In recent years the role of the Southwestern Atlantic Ocean in the CO 2 uptake has received special attention (Bianchi et al, 2005(Bianchi et al, , 2009Ito et al, 2005Ito et al, , 2016Padin et al, 2010;Arruda et al, 2015;Lencina-Avila et al, 2016;Kahl et al, 2017;Orselli et al, 2018;de Carvalho-Borges et al, 2018;Carvalho et al, 2021;Fontela et al, 2021;Liutti et al, 2021;de Oliveira Carvalho et al, 2022), though this region still remains under-sampled. Specifically regarding the shelf areas in the Southwestern Atlantic, as result of the relevance of biological processes (mainly primary production) on the sea-air CO 2 exchange a contrasting behavior of CO 2 sink-source to the north (source) and south (sink) of 35°S was found, acting as two distinct biogeochemical regions (de Oliveira Carvalho et al, 2022).…”

“…Along with the recognition of its high biological productivity, previous studies denoted that the Argentine shelf and slope waters are an important CO 2 sink area (0.02 Pg C yr -1 for the 38°S-55°S latitude band; Kahl et al, 2017) that exhibits a highly seasonal CO 2 dynamic, with marked differences north and south of 47°S, and strong gradients in the frontal regions (Bianchi al., 2005(Bianchi al., , 2009Schloss et al, 2007;Padin et al, 2010;Kahl et al, 2017;Orselli et al, 2018). According to these studies, the biological pump dominates the sea-air exchange of CO 2 , though the role of plankton communities affecting the carbonate system variability is still poorly understood (see Schloss et al, 2007;Carvalho et al, 2021;de Oliveira Carvalho et al, 2022).…”

“…the Argentine anchovy Engraulis anchoita and the Argentine hake Merluccius hubbsi); being a spawning and breeding area for several species of fish (Auad and Martos, 2012;Marrari et al, 2013;Temperoni et al, 2021). Despite several studies in the area have emphasized the strong influence of both biology and the thermohaline regime in modulating the CO 2 distribution (Kahl et al, 2017;Kahl, 2018;Orselli et al, 2018;de Oliveira Carvalho et al, 2022), many aspects of its dynamics remain undetermined. The complexity of this area highlights the importance of conducting smallscale observations to reduce the uncertainty of the ocean CO 2 uptake when considering its contribution on the carbon budget at a large scale.…”