Contrasting drivers and trends of ocean acidification in the subarctic Atlantic
Fı́z F. Pérez, Jón Ólafsson, Sólveig Rósa Ólafsdóttir, Marcos Fontela, Taro Takahashi
Abstract
Abstract The processes of warming, anthropogenic CO 2 (C anth ) accumulation, decreasing pH T (increasing [H + ] T ; concentration in total scale) and calcium carbonate saturation in the subarctic zone of the North Atlantic are unequivocal in the time-series measurements of the Iceland (IS-TS, 1985–2003) and Irminger Sea (IRM-TS, 1983–2013) stations. Both stations show high rates of C anth accumulation with different rates of warming, salinification and stratification linked to regional circulation and dynamics. At the IS-TS, advected and stratified waters of Arctic origin drive a strong increase in [H + ] T , in the surface layer, which is nearly halved in the deep layer (44.7 ± 3.6 and 25.5 ± 1.0 pmol kg −1 yr −1 , respectively). In contrast, the weak stratification at the IRM-TS allows warming, salinification and C anth uptake to reach the deep layer. The acidification trends are even stronger in the deep layer than in the surface layer (44.2 ± 1.0 pmol kg −1 yr −1 and 32.6 ± 3.4 pmol kg −1 yr −1 of [H + ] T , respectively). The driver analysis detects that warming contributes up to 50% to the increase in [H + ] T at the IRM-TS but has a small positive effect on calcium carbonate saturation. The C anth increase is the main driver of the observed acidification, but it is partially dampened by the northward advection of water with a relatively low natural CO 2 content.