Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, 50935 Cologne, Germany.
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA.
Nature. 2014 Jun 5;510(7503):134-8. doi: 10.1038/nature13397. Epub 2014 May 28.
Our understanding of the deglacial evolution of the Antarctic Ice Sheet (AIS) following the Last Glacial Maximum (26,000-19,000 years ago) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences. This sparseness limits our understanding of the dominant feedbacks between the AIS, Southern Hemisphere climate and global sea level. Marine records of iceberg-rafted debris (IBRD) provide a nearly continuous signal of ice-sheet dynamics and variability. IBRD records from the North Atlantic Ocean have been widely used to reconstruct variability in Northern Hemisphere ice sheets, but comparable records from the Southern Ocean of the AIS are lacking because of the low resolution and large dating uncertainties in existing sediment cores. Here we present two well-dated, high-resolution IBRD records that capture a spatially integrated signal of AIS variability during the last deglaciation. We document eight events of increased iceberg flux from various parts of the AIS between 20,000 and 9,000 years ago, in marked contrast to previous scenarios which identified the main AIS retreat as occurring after meltwater pulse 1A and continuing into the late Holocene epoch. The highest IBRD flux occurred 14,600 years ago, providing the first direct evidence for an Antarctic contribution to meltwater pulse 1A. Climate model simulations with AIS freshwater forcing identify a positive feedback between poleward transport of Circumpolar Deep Water, subsurface warming and AIS melt, suggesting that small perturbations to the ice sheet can be substantially enhanced, providing a possible mechanism for rapid sea-level rise.
我们对末次冰期最大值（距今 26000-19000 年）后南极冰盖（AIS）的去冰演化的理解主要基于少数几个定年良好但时间和空间上受限的陆地和浅海序列。这种稀疏性限制了我们对 AIS、南半球气候和全球海平面之间主要反馈的理解。冰山漂流碎屑（IBRD）的海洋记录提供了冰盖动力学和可变性的近乎连续信号。来自北大西洋的 IBRD 记录已被广泛用于重建北半球冰盖的可变性，但由于现有沉积核心的分辨率低和定年不确定性大，缺乏来自 AIS 南大洋的可比记录。在这里，我们提出了两个定年良好、高分辨率的 IBRD 记录，这些记录捕获了末次冰消期 AIS 可变性的空间综合信号。我们记录了在 2 万至 9000 年前，AIS 不同地区冰架通量增加的 8 个事件，与之前的情景形成鲜明对比，之前的情景确定了 AIS 的主要后退发生在 1A 融水脉冲之后，并持续到全新世晚期。IBRD 通量最高发生在 14600 年前，这为 AIS 对 1A 融水脉冲的贡献提供了第一个直接证据。具有 AIS 淡水强迫的气候模型模拟确定了绕极深海水体向极地输送、次表层变暖与 AIS 融化之间的正反馈，表明对冰盖的微小干扰可以大大增强，为海平面快速上升提供了一种可能的机制。
