Air-sea coupling shapes North American hydroclimate response to ice sheets during the Last Glacial Maximum
Air-sea coupling shapes North American hydroclimate response to ice sheets during the Last Glacial Maximum
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DOI：
10.1016/j.epsl.2021.117271
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发表时间：
2021-11
影响因子：
5.3
通讯作者：
D. Amaya;A. Seltzer;K. Karnauskas;J. Lora;Xiyue Zhang;P. DiNezio
中科院分区：
文献类型：
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作者：
D. Amaya;A. Seltzer;K. Karnauskas;J. Lora;Xiyue Zhang;P. DiNezio
美国西部容易受到水文压力的影响，过去气候时期的见解有助于为未来气候预测提供历史基准。来自耦合模型和古气候代理的大量证据表明，在末次冰期最大期（LGM，17-25 ka），西海岸水文气候发生了重大重组，美国西南部比现代更潮湿，太平洋西北部更干燥。然而，这些水文气候变化的基本机制仍然不清楚。在这里，我们采用了一套有针对性的模式模拟探测LGM北方半球冰盖对西海岸大气动力学的影响。而以前的建模研究表明，LGM西海岸降水的南移是由高架冰盖地形大气环流的机械转向驱动的，我们发现这是一个人工制品的早期模拟，忽略了现实的海气相互作用。相反，我们的模拟结果表明，冰盖融化引起的北太平洋海面温度的模式，加强了海洋-大气反馈，大规模的大气环流以及西海岸降水的纬度分布向南LGM期间。至关重要的是，我们发现，在LGM中维持这种冰盖温度模式的大气-海洋反馈可能会驱动今天类似的水文气候变化。
The Western U.S. is vulnerable to hydrological stress, and insights from past climate periods are helpful for providing historical benchmarks for future climate projections. Myriad evidence from coupled models and paleoclimatic proxies suggests a major reorganization of west coast hydroclimate during the Last Glacial Maximum (LGM, ∼17–25 ka), such that the Southwest U.S. was wetter than modern day and the Pacific Northwest was drier. Yet the fundamental mechanisms underlying these hydroclimatic shifts remain unclear. Here, we employ a suite of targeted model simulations to probe the influence of LGM Northern Hemisphere ice sheets on west coast atmospheric dynamics. Whereas previous modeling studies have suggested that the southward shift of LGM west coast precipitation was driven only by the mechanical steering of atmospheric circulation by elevated ice sheet topography, we find this to be an artifact of earlier simulations that neglected realistic air-sea interaction. Instead, our simulations indicate that ice sheet albedo induced a pattern of North Pacific sea surface temperatures, reinforced by ocean-atmosphere feedbacks, that shifted the large-scale atmospheric circulation as well as the latitudinal distribution of west coast precipitation southward during the LGM. Crucially, we find that atmosphere-ocean feedbacks that sustained this ice sheet albedo-induced temperature pattern in the LGM could drive similar hydroclimatic changes today.