Robust modern gradients in sea surface temperature (SST) and biological productivity across the eastern equatorial Pacific (EEP) Ocean between 80° and 140°W derive from vigorous upwelling of cold and nutrient-rich waters. However, during the mid-Pliocene warm period (3.0–3.3 Ma), the zonal SST gradient within the EEP was reduced to <0.5°C while the productivity gradient remained as strong if not stronger than modern. We consider the oceanographic mechanisms and external climate forcings responsible for the evolution of the SST-productivity coupling. We synthesize existing records and present new reconstructions of alkenone biomarker SST and productivity from four EEP sites. The progressive SST gradient strengthening over the Plio-Pleistocene contrasted with the stronger Late Pliocene surface productivity gradient relative to modern. Dominance of the oceanic tunnel over surface forcings best explains these observations: SST changes reflect extratropical water masses cooling toward the present while productivity proxies suggest these waters became less nutrient-rich.

中文翻译：

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过去 3.6 Myr 东赤道太平洋表面温度和生产力的海洋隧道控制


东赤道太平洋 （EEP） 海洋 80° 至 140°W 之间海面温度 （SST） 和生物生产力的强劲现代梯度源于寒冷和营养丰富的水域的强劲上升流。然而，在上新世中期温暖期（3.0–3.3 马），EEP 内的纬向 SST 梯度降低到 <0.5°C，而生产力梯度保持与现代一样强，甚至更强。我们考虑了导致 SST -生产力耦合演变的海洋学机制和外部气候强迫。我们综合了现有记录，并提出了来自四个 EEP 位点的烯酮生物标志物 SST 和生产率的新重建。上更新世的渐进式 SST 梯度增强与相对于现代的上新世晚期地表生产力梯度增强形成鲜明对比。海洋隧道对表面强迫的主导地位最能解释这些观察结果：SST 变化反映了温带水团向现在冷却，而生产力代理表明这些水域的营养变得不那么丰富。