Carbonate system in the water masses of the Southeast Atlantic sector of the Southern Ocean during February and March 2008

• Published in: Biogeosciences
• Main Authors: González-Dávila, M., Santana-Casiano, J. M., Fine, R. A., Happell, J., Delille, B., Speich, S.
• Other Authors: Speich, Sabrina, SANTANA CASIANO, JUANA MAGDALENA, Delille, Bruno, GONZALEZ DAVILA, MELCHOR, 6603931257, 6701344294, 7201538303, 6602193023, 6602185381, 6602115663, 518149, 579253, 465296, 1931953, 484917, 616508
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10553/6216; https://doi.org/10.5194/bg-8-1401-2011

Carbonate system variables were measured in the\nSouth Atlantic sector of the Southern Ocean along a transect\nfrom South Africa to the southern limit of the Antarctic Circumpolar\nCurrent (ACC) from February to March 2008. Eddies\ndetached from the retroflection of the Agulhas Current\nincreased the gradients observed along the fronts. Minima\nin the fugacity of CO2, fCO2, and maxima in pH on either\nside of the frontal zone were observed, noting that within the\nfrontal zone fCO2 reached maximum values and pH was at\na minimum.Vertical distributions of water masses were described\nby their carbonate system properties and their relationship\nto CFC concentrations. Upper Circumpolar Deep Water\n(UCDW) and Lower Circumpolar Deep Water (LCDW)\noffered pHT,25 values of 7.56 and 7.61, respectively.\nThe UCDW also had higher concentrations of CFC-12\n(>0.2 pmol kg?1) as compared to deeper waters, revealing\nthat UCDW was mixed with recently ventilated waters. Calcite\nand aragonite saturation states ( ) were also affected\nby the presence of these two water masses with high carbonate\nconcentrations. The aragonite saturation horizon was\nobserved at 1000m in the subtropical area and north of the\nSubantarctic Front. At the position of the Polar Front, and\nunder the influence of UCDW and LCDW, the aragonite saturation\nhorizon deepened from 800m to 1500m at 50.37_ S,\nand reached 700m south of 57.5_ S. High latitudes proved\nto be the most sensitive areas to predicted anthropogenic carbon\nincrease. Buffer coefficients related to changes in [CO2],\n[H+] and with changes in dissolved inorganic carbon (CT)and total alkalinity (AT) offered minima values in the Antarctic\nIntermediateWater and UCDWlayers. These coefficients\nsuggest that a small increase in CT will sharply decrease\nthe status of pH and carbonate saturation. Here we present\ndata that suggest that south of 55_ S, surface water will be\nunder-saturated with respect to aragonite within the next few\ndecades.