Supplementary material: XRF core scanning data, CaCO3 values, foraminiferal carbon and oxygen isotope data, Mg/Ca data, clay mineralogy and helium isotope results

The Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) is associated with abrupt climate change, carbon cycle perturbation, ocean acidification, as well as biogeographic shifts in marine and terrestrial biota that were largely reversed as the climatic transient waned. We report a clear exception to the behavior of the PETM as a reversing climatic transient in the eastern North Atlantic (Deep-Sea Drilling Project Site 401, Bay of Biscay) where the PETM initiates a greatly prolonged environmental change compared to other places on Earth where records exist. The observed environmental perturbation extended well past the d13C recovery phase and up to 650 kyr after the PETM onset according to our extraterrestrial 3He-based age-model. We observe a strong decoupling of planktic foraminiferal d18O and Mg/Ca values during the PETM d13C recovery phase, which in combination with results from helium isotopes and clay mineralogy, suggests that the PETM triggered a hydrologic change in western Europe that increased freshwater flux and the delivery of weathering products to the eastern North Atlantic. This state change persisted long after the carbon-cycle perturbation had stopped. We hypothesize that either long-lived continental drainage patterns were altered by enhanced hydrological cycling induced by the PETM, or alternatively that the climate system in the hinterland area of Site 401 was forced into a new climate state that was not easily reversed in the aftermath of the PETM.古新世-始新世极热事件（Paleocene-Eocene Thermal Maximum, PETM；约56 Ma）与突发性气候突变、碳循环扰动、海洋酸化以及海陆生物群的生物地理分布变迁紧密关联，且上述生物地理变化在气候瞬变衰减过程中基本得以逆转。我们报道了北大西洋东部（比斯开湾深海钻探计划（Deep-Sea Drilling Project, DSDP）401站位）处PETM作为可逆气候瞬变行为的显著例外：与全球其他有相关记录的区域相比，该站位的PETM引发了大幅延长的环境变化。基于我们构建的地外氦3（extraterrestrial ³He）年代模型，本次观测到的环境扰动远超δ¹³C恢复阶段，且持续至PETM起始后65万年之久。我们在PETM的δ¹³C恢复阶段观测到浮游有孔虫（planktic foraminiferal）的δ¹⁸O与Mg/Ca比值出现强烈解耦现象；结合氦同位素与黏土矿物学的研究结果，这表明PETM触发了西欧的水文变化，使得淡水通量与风化产物向北大西洋东部的输送量显著提升。这种状态转变在碳循环扰动结束后仍持续了极长时间。我们提出两种假说：一是PETM诱导的增强水文循环改变了长期稳定的大陆径流格局；二是401站位腹地的气候系统被强制进入了一种在PETM后难以快速逆转的全新气候状态。