Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska
Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska
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DOI：
10.1016/j.quascirev.2017.05.012
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发表时间：
2017-08-01
影响因子：
4
通讯作者：
Reanier, Richard E.
中科院分区：
文献类型：
--
作者：
Gaglioti, Benjamin V.;Mann, Daniel H.;Reanier, Richard E.
目前，海冰范围的缩小正在加剧北极的气候变暖。高纬度地区的仪器记录时间太短，无法为这些趋势提供足够的历史背景，因此需要古气候档案来更好地了解海冰反照率反馈的功能。在这里，我们使用经过放射性碳测年 (C-14) 的活体和亚化石柳灌木 (delta O-18(wc))（柳属）中木质纤维素的氧同位素值，生成更新世-全新世过渡期间阿拉斯加北坡气候变化的千年记录（13,500-7500 校准于 14C 年前； 13.5-7.5ka）。我们首先分析了生长在高地的活柳的 Delta O-18(wc) 的时空模式，发现在过去 30 年中各个生长轮中的 Delta O-18(wc) 值与当地夏季温度和夏季海冰范围的年际变化相关。 145 个亚化石柳样本的冰消期 δ O-18(wc) 值清楚地记录了阿勒罗德暖期（类似于 13.2 ka）、新仙女木寒冷期（12.9-11.7 ka）和全新世最热期（11.7-9.0 ka）。这些快速气候振荡导致的同位素变化幅度约为千分之 4.5，这大约是末次冰期和今天生长的柳树之间 Delta O-18(wc) 差异的 60%。基于瑞利蒸馏过程的同位素-降水关系模型表明，在新仙女木期，6180,c 值的这些巨大变化是由当地温度和蒸发水分源变化之间的相互作用引起的，后者受北冰洋和白令海海冰范围的控制。根据这些结果以及海冰对当今气候的影响，我们推断，在过去的温暖时期，来自海洋的反馈放大了阿拉斯加北极沿海地区的温度变化并增加了降水。如今，阿拉斯加北坡柳树的同位素值与更新世-全新世过渡期最温暖时期生长的柳树的同位素值相似，当时的永久冻土层广泛融化，生态发生了显着变化。 (C) 2017 Elsevier Ltd. 保留所有权利。
Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (delta O-18(wc)) (Salix spp.) that have been radiocarbon-dated (C-14) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500-7500 calibrated 14C years before present; 13.5-7.5 ka). We first analyzed the spatial and temporal patterns of delta O-18(wc) in living willows growing at upland sites and found that over the last 30 years delta O-18(wc) values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial delta O-18(wc) values from 145 samples of subfossil willows clearly record the Allerod warm period (similar to 13.2 ka), the Younger Dryas cold period (12.9-11.7 ka), and the Holocene Thermal Maximum (11.7-9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were similar to 4.5 parts per thousand, which is about 60% of the differences in delta O-18(wc) between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in 6180,c values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar to those growing during the warmest times of the Pleistocene-Holocene transition, which were times of widespread permafrost thaw and striking ecological changes. (C) 2017 Elsevier Ltd. All rights reserved.