Fig. 2: CB-δ15N master record and comparison to the AMO.
From: Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms
a, The normalized master CB-δ15N record (z scores) with the propagated error (±1s.d., shaded region) is based on four coral cores (Belize, Cuba, Martinique and Mexico from 1900 to 2021) from the wider Caribbean region and is closely related to Caribbean nitrate δ15N. Higher normalized CB-δ15N values correspond to lower rates of N2 fixation, whereas lower normalized CB-δ15N values are indicative of higher N2 fixation rates. b, Compared with a is the AMO index derived from Trenberth and Shea52 (black line) and the locally estimated scatterplot smoothing (LOESS) of depth-integrated P* values of the equatorial North Atlantic (−10 to 30° N, 20 to 60° W) from the GLODAPv2.2022 dataset for the period of 1981–2020 (orange line). The mean LOESS-smoothed P* values show congruent variability with the AMO. Positive AMO phases (red bars) represent a warmer North Atlantic compared with the South Atlantic, whereas negative AMO phases (blue bars) represent a colder North Atlantic compared with the South Atlantic. The positive AMO states correspond to a northward displacement of the ITCZ; negative AMO states indicate a southward displacement of the ITCZ.
