Fig. 4: Satellite-derived Fe limitation.
From: Persistent equatorial Pacific iron limitation under ENSO forcing
a, Regional pattern of \({F/{\rm{Chl}}}_{{\rm{passive}}}^{{\rm{sat}}}\), reflecting the level of Fe limitation, for a MODIS-Aqua boreal winter climatological average. The white rectangle highlights the Niño3 region, with dot-dashed lines defining the core upwelling zone. Regions of the ocean with no data have chlorophyll a either below the satellite fluorescence detection limit or higher than our validated range. b, Longitudinally averaged changes in monthly \({F/{\rm{Chl}}}_{{\rm{passive}}}^{{\rm{sat}}}\) and chlorophyll a in relation to mean Niño3 region SSTs for the MODIS record. Dashed lines define the latitude range for the core of the upwelling zone. c,d, Left: time series of chlorophyll a and \({F/{\rm{Chl}}}_{{\rm{passive}}}^{{\rm{sat}}}\) anomalies (value minus record average) for the central Niño3 region. Right: scatter plot correlations showing type II linear regressions (ranged major axis; red lines) and the 95% confidence regions for the regression lines (grey lines). The R2 and P values (two-tailed) for the regression significance test are shown (no adjustment for multiple comparisons). e, Pacific-wide distribution of \({F/{\rm{Chl}}}_{{\rm{passive}}}^{{\rm{sat}}}\) (boreal winter climatological average) scaled to model limitation range (left) and model Fe limitation (right). f, Fe-limitation sensitivity to temperature changes in the central Niño3 region for the model (grey dots, R2 = 0.82; P = 9.4 × 10−281; slope = 0.06) and derived from \({F/{\rm{Chl}}}_{{\rm{passive}}}^{{\rm{sat}}}\) (green dots, R2 = 0.50; P = 4.39 × 10−35; slope = 0.029); regression lines and statistics as for c,d.
