Repeated near-collapse of the Pliocene sea surface temperature gradient in the North Atlantic

Sea surface temperature (SST) are used to infer past changes in the state of the climate system. Here we use a combination of newly generated and published organic paleothermometer records, together with novel high-resolution benthic foraminiferal δ18 24 O stratigraphy, from four sites in the mid-latitude North Atlantic (41-58 °N) to reconstruct the long-term evolution of the latitudinal SST gradient during the Pliocene and early Pleistocene (4.0 to 2.4 Myr), the last time atmospheric CO2 reached concentrations above 400 ppmv. We demonstrate that the latitudinal SST gradient in the North Atlantic nearly collapsed twice during this period. We conclude that the latitudinal SST gradient in the mid-latitude North Atlantic has two end-members; a maximum as existing at present and a minimum that existedduring certain periods of the (late) Pliocene. Our results suggest that the 400 ppmv Plioceneworld was much more dynamic than currently thought.