a, Satellite backscatter bbp relative anomaly for the 2019–2020 austral summer. Bloom region and BGC-Argo float trajectories superimposed on the map. Float positions from September 2019 through March 2020 highlighted. The southern float (red) was in a biologically more active region of the bloom than the two northern floats (blue and yellow). This corroborates the stronger bloom signal shown by the southern float. Dotted, dot-dashed, and solid lines in a represent the climatological positions of the Subtropical Front, Subantarctic Front and Polar Front, respectively48. b, Satellite bbp averaged over two sub-regions encompassing the float paths. The solid lines are 2019–2020 observations and the dotted lines with coloured standard deviation envelopes are the climatology. This analysis corroborates the stronger bloom signal shown by the southern float compared with the two northern floats. c, Comparison between uncalibrated (dashed lines) and calibrated (solid lines) in situ bbp measured by the three BGC-Argo floats. Surface bbp estimates were calculated as the median bbp between 0 and 20 m depth and then calibrated using a linear regression (see Methods for details). The calibration was applied to allow for comparison between float bbp and the satellite-based climatology. The general trend of the float signal is not altered by the calibration.