Integrated phytoplankton carbon: subsurface carbon. The de-seasonalized data were extracted from column-integrated (1.5 Zp) concentrations (Methods). Light coloured lines, linear regression fitted to the entire time series (1990–2022); thick dashed black lines, linear regressions fitted to de-seasonalized data to the end of 2010 (pre-2011 includes 1990–2010); thick solid black lines, linear regressions fitted to de-seasonalized data only from 2011 to the end of 2022 (post 2011 includes 2011–2022); S, slope of the trend; and P, significance of the trend from Pearson correlation; yellow dashed lines, monthly AMO index to March 2021 from the National Center for Atmospheric Research (Data Availability) with Spearman correlation coefficient (R) and significance (P) of the correlation with the de-seasonalized data. See Supplementary Fig. 1 for cumulative Chl-a anomalies superimposed on cumulative AMO, showing a similarly strong relationship between surface Chl-a and the AMO index. See Supplementary Fig. 2 for cumulative C:Chl ratio anomalies superimposed on cumulative AMO, illustrating similar relationships with the AMO index. See Supplementary Fig. 3 for a similar trend analysis based on concentrations instead of integrated stocks.
