MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, 28359, Germany.
GEOMAR, Helmholtz Centre for Ocean Research Kiel, Kiel, 24148, Germany.
Nat Commun. 2022 Jul 21;13(1):4217. doi: 10.1038/s41467-022-31754-x.
Although the global environmental impact of Laurentide Ice-Sheet destabilizations on glacial climate during Heinrich Events is well-documented, the mechanism driving these ice-sheet instabilities remains elusive. Here we report foraminifera-based subsurface (~150 m water depth) ocean temperature and salinity reconstructions from a sediment core collected in the western subpolar North Atlantic, showing a consistent pattern of rapid subsurface ocean warming preceding the transition into each Heinrich Event identified in the same core of the last 27,000 years. These results provide the first solid evidence for the massive accumulation of ocean heat near the critical depth to trigger melting of marine-terminating portions of the Laurentide Ice Sheet around Labrador Sea followed by Heinrich Events. The repeated build-up of a subsurface heat reservoir in the subpolar Atlantic closely corresponds to times of weakened Atlantic Meridional Overturning Circulation, indicating a precursor role of ocean circulation changes for initiating abrupt ice-sheet instabilities during Heinrich Events. We infer that a weaker ocean circulation in future may result in accelerated interior-ocean warming of the subpolar Atlantic, which could be critical for the stability of modern, marine-terminating Arctic glaciers and the freshwater budget of the North Atlantic.
尽管拉普兰冰盖在 Heinrich 事件期间对冰川气候的全球环境影响已有充分记录，但驱动这些冰盖不稳定的机制仍难以捉摸。在这里，我们报告了来自北大西洋西部亚极地深海沉积物岩芯中基于有孔虫的约 150 米水深的海洋温度和盐度重建，结果显示在过去 27000 年中同一岩芯中识别出的每个 Heinrich 事件之前，存在快速的深海变暖的一致模式。这些结果为大量海洋热量在关键深度附近积累提供了确凿的证据，这些热量的积累触发了拉普兰冰盖海洋终止部分的融化，随后是 Heinrich 事件的发生。在北大西洋亚极地，深海热量储存的反复积累与大西洋经向翻转环流减弱的时期密切对应，这表明海洋环流变化在 Heinrich 事件期间引发突然的冰盖不稳定方面发挥了前兆作用。我们推断，未来较弱的海洋环流可能导致亚极地大西洋内部海洋加速变暖，这对现代海洋终止的北极冰川和北大西洋淡水预算的稳定性可能至关重要。
