R. Steinfeldt et al.: Anthropogenic carbon in the Atlantic 3857 Figure 12. Zonal mean sections of1tCanomant (Cant forecast based on tracer data from the first period minus Cant based on tracer data from the second period). (a, c, e) Western basin, (b, d, f) eastern basin, (a, b) 1990–2000, (c, d) 2000–2010, (e, f) 2010–2020. Regions with differences smaller than the error range are stippled. Contour lines are shown as in Fig. 2. Note the uneven spacing between contour intervals. on the decadal forecasts (e.g., Cant1990?2000 ? Cant1990). In the South Atlantic, 1tCanomant is negative, especially for the 1990–2000 period. This implies a decrease in Cant storage due to changes in circulation and/or ventilation for the 1990– 2000 decade compared to the period before 1990 and af- ter 2000. Müller et al. (2023) also find a strong Cant in- crease over the South Atlantic from their first (1994–2004) to their second decade (2004–2014). All other numbers in Table 6 are not significantly different from 0. Thus, at least for the Atlantic as a whole, the Cant increase over the last 30 years is almost in agreement with the rising atmospheric CO2. On smaller regional scales, however, there are regions where 1tCanomant is statistically significantly different from 0 (Fig. 12). In general, the local extrema of 1tCanomant are about ± 5 µmol kg?1, the same magnitude as in Gruber et al. (2019). The zonal mean section of the Cant accumulation anomaly obtained for the western Atlantic for the periods of 1990– 2000, 2000–2010 and 2010–2020 (Fig. 12a, c and e) shows some areas with extreme values of 1tCanomant that are simi- lar for all three decadal periods. One is located in the South Atlantic within the AAIW; one in the tropics (20° S–20° N) above the AAIW; and one in the North Atlantic in the Central Water, LSW, ISOW and DSOW. https://doi.org/10.5194/bg-21-3839-2024 Biogeosciences, 21, 3839–3867, 2024