Praetorius Summer K, Condron Alan, Mix Alan C, Walczak Maureen H, McKay Jennifer L, Du Jianghui
U.S. Geological Survey, Menlo Park, CA, USA.
Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Sci Adv. 2020 Feb 26;6(9):eaay2915. doi: 10.1126/sciadv.aay2915. eCollection 2020 Feb.
Columbia River megafloods occurred repeatedly during the last deglaciation, but the impacts of this fresh water on Pacific hydrography are largely unknown. To reconstruct changes in ocean circulation during this period, we used a numerical model to simulate the flow trajectory of Columbia River megafloods and compiled records of sea surface temperature, paleo-salinity, and deep-water radiocarbon from marine sediment cores in the Northeast Pacific. The North Pacific sea surface cooled and freshened during the early deglacial (19.0-16.5 ka) and Younger Dryas (12.9-11.7 ka) intervals, coincident with the appearance of subsurface water masses depleted in radiocarbon relative to the sea surface. We infer that Pacific meltwater fluxes contributed to net Northern Hemisphere cooling prior to North Atlantic Heinrich Events, and again during the Younger Dryas stadial. Abrupt warming in the Northeast Pacific similarly contributed to hemispheric warming during the Bølling and Holocene transitions. These findings underscore the importance of changes in North Pacific freshwater fluxes and circulation in deglacial climate events.
在末次冰消期，哥伦比亚河多次发生大洪水，但这些淡水对太平洋水文的影响在很大程度上尚不明确。为了重建这一时期海洋环流的变化，我们使用数值模型来模拟哥伦比亚河大洪水的流动轨迹，并汇编了东北太平洋海洋沉积物岩芯的海面温度、古盐度和深水放射性碳记录。在早冰消期（19.0 - 16.5 ka）和新仙女木期（12.9 - 11.7 ka）期间，北太平洋海面变冷且变淡，这与相对于海面放射性碳含量减少的次表层水体的出现相吻合。我们推断，太平洋融水通量在北大西洋 Heinrich 事件之前以及新仙女木期阶段再次导致了北半球的净降温。东北太平洋的突然变暖同样在博林期和全新世过渡期间促成了半球变暖。这些发现强调了北太平洋淡水通量和环流变化在冰消期气候事件中的重要性。
