Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands.
Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway.
Sci Adv. 2023 Jan 25;9(4):eabq0110. doi: 10.1126/sciadv.abq0110.
Quantitative reconstructions of hydrological change during ancient greenhouse warming events provide valuable insight into warmer-than-modern hydrological cycles but are limited by paleoclimate proxy uncertainties. We present sea surface temperature (SST) records and seawater oxygen isotope (δO) estimates for the Middle Eocene Climatic Optimum (MECO), using coupled carbonate clumped isotope (Δ) and oxygen isotope (δO) data of well-preserved planktonic foraminifera from the North Atlantic Newfoundland Drifts. These indicate a transient ~3°C warming across the MECO, with absolute temperatures generally in accordance with trace element (Mg/Ca)-based SSTs but lower than biomarker-based SSTs for the same interval. We find a transient ~0.5‰ shift toward higher δO, which implies increased salinity in the North Atlantic subtropical gyre and potentially a poleward expansion of its northern boundary in response to greenhouse warming. These observations provide constraints on dynamic ocean response to warming events, which are consistent with theory and model simulations predicting an enhanced hydrological cycle under global warming.
定量重建古温室变暖事件期间的水文变化，为更温暖的现代水文循环提供了有价值的见解，但受到古气候代用指标不确定性的限制。我们利用北大西洋纽芬兰漂移中保存完好的浮游有孔虫的碳酸盐簇同位素 (Δ) 和氧同位素 (δO) 数据，提供了中始新世气候最优期 (MECO) 的海面温度 (SST) 记录和海水氧同位素 (δO) 估计。这些数据表明，在 MECO 期间发生了一次短暂的约 3°C 的变暖，绝对温度通常与微量元素 (Mg/Ca)-基 SST 一致，但比同一时期基于生物标志物的 SST 低。我们发现了一个短暂的约 0.5‰ 的 δO 向更高值的偏移，这意味着北大西洋亚热带环流的盐度增加，并且可能响应温室变暖而向北扩展其北部边界。这些观测结果为动态海洋对变暖事件的响应提供了限制，与预测全球变暖下增强的水文循环的理论和模型模拟一致。
