Multi-proxy stalagmite records from northern California reveal dynamic patterns of regional hydroclimate over the last glacial cycle
Multi-proxy stalagmite records from northern California reveal dynamic patterns of regional hydroclimate over the last glacial cycle
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DOI：
10.1016/j.quascirev.2020.106411
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发表时间：
2020-08
影响因子：
4
通讯作者：
J. Oster;I. Weisman;W. Sharp
中科院分区：
文献类型：
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作者：
J. Oster;I. Weisman;W. Sharp
尽管它对加州的水资源很重要，但除了历史记录之外，人们对加州北部的降水变化知之甚少。我们提出了一个新的，多代理的古气候记录，来自加利福尼亚州沙斯塔湖洞穴(LSC)的两个同时代石笋，涵盖了海洋同位素阶段3到Heinrich Staial 1(∼35,000年到14,000年BP)的结束。在40.8°N，LSC位于美国西北部和西南部地区之间的过渡地带，这两个地区对现代和古气候驱动因素表现出不同的降水响应。LSC石笋的稳定同位素和微量元素替代物表明，该地区在与Dansgaard-Oeschger旋回相关的间歇期(暖期)经历了潮湿的条件，类似于来自俄勒冈州南部和大盆地北部的替代记录，但与来自西南沙漠的记录相反。与北部的喀斯喀兹山脉和落基山脉相似，LSC在最后一次冰川盛期更为干燥。然而，代理数据显示，整个海因里希阶梯1号的降雨量增加，类似于大盆地和西南部。因此，LSC记录显示了过渡区位置的非平稳性，并说明了美国西部降水对全球气候变化的复杂响应模式。指示水分来源的洞穴δ18O与指示水分数量的δ13C和微量元素的协变表明，尽管干旱加剧，但在最后一次冰盛期期间，中太平洋降水的比例更高。相反，以降水量增加为特征的时期，如海因里希1早期，与来自北太平洋的水汽增加有关。
Despite its importance for California’s water resources, little is known about how precipitation has varied in far northern California beyond the historical record. We present a new, multi-proxy paleoclimate record derived from two coeval stalagmites from Lake Shasta Caverns (LSC), California that covers the end of Marine Isotope Stage 3 through Heinrich Stadial 1 (∼35,000 to 14,000 years BP). At 40.8°N, LSC is situated within the transition zone between regions in the northwestern and southwestern United States that demonstrate different precipitation responses to both modern and paleoclimatic drivers. Stable isotope and trace element proxies from LSC stalagmites indicate the region experienced wet conditions during interstadials (warm periods) associated with Dansgaard-Oeschger cycles, similar to proxy records from southern Oregon and the northern Great Basin, but in contrast to records from the desert southwest. Similar to the northern Cascades and Rocky Mountains, LSC was drier during the Last Glacial Maximum. However, proxies indicate increased rainfall throughout Heinrich Stadial 1, similar to the Great Basin and southwest. Thus, the LSC record demonstrates the non-stationarity of the transition zone location and illustrates a complex pattern of precipitation response to global climate change in the western United States. Covariation of speleothemδ18O, an indicator of moisture source, withδ13C and trace elements, indicators of moisture amount, suggest a higher proportion of Central Pacific precipitation during the Last Glacial Maximum, despite the enhanced aridity. In contrast, periods characterized by increased precipitation amounts, such as early Heinrich 1, are associated with enhanced moisture from the Northern Pacific.