Fig. 1.
Current day Chl-a and its interannual variability. Composite mean Chl-a (mg Chl m−3) for 1998–2015: a model actual; b model satellite-like derived (using an algorithm and the model RRS,); c Ocean Colour Climate Change Initiative project (OC-CCI, v2) satellite derived. Interannual variability defined as the standard deviation of the annual mean composites (1998–2015): d model actual; e model satellite-like derived; f OC-CCI, v2 satellite derived. White areas are regions where model resolution is too coarse to capture the smaller seas, or where there is persistent ice cover. Statistical comparison of derived model and OC-CCI product are provided in Supplementary Figs. 1–3. Model actual Chl-a is the sum of the dynamic Chl-a for each phytoplankton type that is explicitly resolved in the model. It is equivalent to the Chl-a that would be measured in situ. This is distinct to satellite-derived Chl-a which is calculated via an algorithm derived from the reflected light measured by ocean colour satellite instruments