Extended Data Fig. 3: Extended physical oceanographic model output links pH changes to a Pacific meridional overturning circulation.
From: Pliocene decoupling of equatorial Pacific temperature and pH gradients
a–d, Timeseries of PMOC strength (blue lines), zonal Pacific pH gradient (ΔpH, black lines), and zonal Pacific SST gradient (ΔSST, red lines) for the model control run (a, b) and early Pliocene/late Miocene run (c, d). PMOC strength (Max PMOC Streamfunction) is defined as the maximum streamfunction north of 25°N and below 500 m depth in sverdrups (1 Sv = 106 m3 s−1). The pH gradient is defined as the pH difference between a western (5°S–5°N, 150–170°E) and eastern Pacific box (5°S–5°N, 260–280°E), taken at 55 m depth. The SST gradient is defined as the SST difference between the same boxes taken at the surface. Note that while the zonal SST gradient equilibrates within ~500 years in the early Pliocene/late Miocene experiment (d) and is hardly influenced by the appearance of the PMOC between ~800–1,600 years, the zonal pH gradient increases in phase with the PMOC (c). e–h, Zonally averaged streamfunction over the Pacific (e, g) and Atlantic (f, h) basins for the control run (e, f) and early Pliocene/late Miocene (g, h) runs of the model Positive (green values) denote clockwise circulation, and negative (pink) values denote counterclockwise rotation. Panel g is the same as Fig. 4b in the main text.
