Fig. 2

Temporal variability in sea surface temperature, salinity, and carbonate parameters in January in three latitudinal bands. a–e Sea surface temperature (a, SST), salinity (b, SSS), sea surface CO₂ fugacity (c, fCO₂), estimated total alkalinity (d, TA) and calculated dissolved inorganic carbon (e, DIC) at 60°–55° S. f–j Show the same parameters but at 55°–50° S; k–o also show the same parameters but at 50°–45° S (see 'Methods'). The vertical bars show one standard deviation, which reflects the spatial variability within each latitudinal band. Linear regression analyses were performed for the periods 1991–2000 (blue) and 2001–2011 (black). Slopes (s) and p-values of the regression analyses are also shown (differentiated with blue and black colors for the two periods). A trend of p-value < 0.1 is regarded as statistically significant (90% confidence interval) due to the small sample numbers (<10). Also, the atmospheric CO₂ data (shown as fCO₂) observed at the GCO (Cape Grim, Tasmania) atmospheric CO₂ measurement station (ftp://aftp.cmdl.noaa.gov/data/trace_gases/co2/flask/) and the DIC values computed due solely to the atmospheric CO₂ increase (see 'Methods') are indicated with open gray circles in Fig. 2c, e