Sea surface temperature (SST) is 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 δ¹⁸O stratigraphy, from four sites in the midlatitude 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 midlatitude North Atlantic has two end‐members: a maximum as existing at present and a minimum that existed during certain periods of the (late) Pliocene. Our results suggest that the 400‐ppmv Pliocene world was more dynamic than currently thought.

中文翻译：

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北大西洋上新世海面温度梯度重复近乎崩溃

海面温度（SST）用于推断气候系统状态的过去变化。这里，我们使用的新生成并公布有机paleothermometer记录的组合，具有新颖高分辨率一起底栖有孔虫δ ¹⁸ ö地层，从纬度北大西洋（41-58°N）四个位点来重建的长期演进上新世和早更新世（4.0到2.4 Myr），最后一次大气CO ₂的纬度SST梯度达到高于400 ppmv的浓度。我们证明了在此期间北大西洋的纬向海温梯度几乎崩溃了两次。我们得出的结论是，北大西洋中纬度的纬向海温梯度具有两个末端成员：目前存在的最大值和上新世的某些时期存在的最小值。我们的结果表明，400-ppmv的上新世世界比现在想象的要动态。