Fig. 4

Impacts of SAM associated winds on acidification rates. a, b rates of surface pH (a) and Ω_arag change (b) without atmospheric CO₂ increase versus change rates of January zonal wind speed during two periods of 1991–2000 (blue) and 2001–2011 (black) in the three latitudinal bands of 60°–55° S, 55°–50° S and 50°–45° S. Rates of pH and Ω_arag change without atmospheric CO₂ increase are highly negatively correlated with change rates of zonal wind speed with a correlation coefficient of 0.92 and 0.89, respectively. Rates of pH and Ω_arag change without atmospheric CO₂ increase were the observed rates of pH_{@in situ} and Ω_{arag@in situ} change, subtracting their rates predicted from atmospheric CO₂ increase alone (see 'Methods'). In this figure, negative change rates of pH or Ω_arag denote enhanced acidification compared to that predicted from atmospheric CO₂ increase alone. The bars show one standard deviation of change rates as shown in Fig. 3