Extended Data Figure 6 : Spatial and temporal evolution of mean annual surface ocean pH in the Earth system model cGENIE, shown both for the PETM and for preindustrial and future times.

From: Very large release of mostly volcanic carbon during the Palaeocene–Eocene Thermal Maximum

Extended Data Figure 6

a, Black line, global mean surface ocean pH values across the PETM, from experiment R07sm_Corg (these are our main pH estimates, obtained using the inorganic borate ion calibration and the RH07 age model, and including an assumption of organic carbon burial after the peak PETM). Red circles represent the annual mean pH values at Site 401 (location shown in b) in the model, taken at times in the model simulation that have corresponding δ11B-derived pH data points (see Fig. 3b; note that we do not use all of the observed data points). b, Model-projected spatial pattern of annual mean surface ocean pH at time zero (that is, PETM onset). The star shows the location of Site 401. cf, Model-projected spatial patterns of the annual mean surface ocean pH anomaly compared with time 0, for the highlighted time points from a (5.0, 31.6, 58.2 and 71.5 kyr after onset). g, Model-projected spatial pattern of annual mean surface ocean pH in the modern ocean under pre-industrial (year 1765) atmospheric CO2 levels (278 p.p.m.). The model is configured as described in ref. 74 and driven with a CO2 emissions scenario that is consistent with RCP 6.0. h, i, Model-projected spatial pattern of the annual mean surface ocean pH anomaly compared with that for 1765, at years 2010 and 2050. The scale is as for cf.