The last deglaciation of Alaska and a new benchmark 10Be moraine chronology from the western Alaska Range
The last deglaciation of Alaska and a new benchmark 10Be moraine chronology from the western Alaska Range
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阿拉斯加末次冰消期和来自阿拉斯加西部山脉的新基准 10Be 冰碛年表
DOI：
10.1016/j.quascirev.2022.107549
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发表时间：
2022
影响因子：
4
通讯作者：
Schaefer, Joerg M.
中科院分区：
文献类型：
--
作者：
Tulenko, Joseph P.;Briner, Jason P.;Young, Nicolás E.;Schaefer, Joerg M.
我们报告了50个新的和22个以前的10 Be年龄从15个不同的冰碛峰在阿拉斯加西部范围跨越从末次冰期最大（LGM）终端冰碛到最近的更新世冰碛立即从晚全新世冰碛山谷。冰碛石沉积于21.3 ± 0.8 ka ~ 12.8 ± 0.6 ka之间，其形态地层学特征与之一致，年代学可信度较高。我们的记录，以及我们在阿拉斯加汇编中回顾的关键记录表明，大约在2000年至2005年之间，区域LGM达到了顶峰。21-19 ka。我们的年表，在阿拉斯加的一个单一的山谷分辨率无与伦比，表明从大约2000年开始的冰川衰退。21-18 ka被从ca加速撤退打断。17-16 ka，其次是一段时间的延长冰碛沉积之间约。16和15 ka。在ca. 15 ka的快速冰川退缩被一个重新前进的ca打断。12.8 ka.阿拉斯加的其他年表显示了冰碛沉积的进一步证据。16-15 ka和ca. 13-12 ka。通过在阿拉斯加的最后一次冰川消退冰川退缩的新模式进行比较，几个全球，区域和当地的气候代理，以评估什么样的气候因素控制的时间和速度在阿拉斯加冰川退缩。我们假设，上升的北方夏季日照引起的变暖驱动初始和稳定的冰消从末次冰期终碛位置，直到约。18 ka，之后，全球变暖的CO2浓度上升加速撤退。阿拉斯加冰碛沉积的后续时期与NGRIP冰芯记录中的减少趋势相吻合，在海因里希体育场1（约1000年）的顶点。16-15 ka），并在13和12.5 ka之间的新仙女木早期。虽然高山冰川记录和其他可能影响当地到区域气候的地质事件的时间进行了比较（例如，白令海峡的开放，劳伦蒂德和科迪勒拉冰盖之间的鞍状塌陷，以及后LGM白令海动力学），我们的记录和这些地质事件之间的关系是模糊的。我们认为阿拉斯加的冰川可能对其他区域和全球气候强迫机制更敏感，主要是太阳辐射上升，全球CO2上升，以及通过冰消作用的北方半球海洋环流强迫。
We report 50 new and 22 previously published10Be ages from 15 distinct moraine crests in the western Alaska Range spanning from the Last Glacial Maximum (LGM) terminal moraine to a latest Pleistocene moraine immediately down valley from late Holocene moraines. Moraines were deposited between 21.3 ± 0.8 ka and 12.8 ± 0.6 ka and conform morphostratigraphically, giving us high confidence in the chronology. Our record, and the key records reviewed in our compilation from across Alaska indicate a culmination of the regional LGM between ca. 21–19 ka. Our chronology, unmatched in resolution from a single valley in Alaska, indicates that steady glacier recession from ca. 21–18 ka was punctuated by accelerated retreat from ca. 17–16 ka, followed by a period of prolonged moraine deposition between ca. 16 and 15 ka. After ca. 15 ka rapid glacier retreat was punctuated by a re-advance ca. 12.8 ka. Other chronologies across Alaska show further evidence of moraine deposition between ca. 16–15 ka and ca. 13–12 ka. The emerging pattern of glacier retreat through the last deglaciation in Alaska is compared to several global, regional, and local climate proxies to assess what climate factors controlled the timing and pace of glacier retreat in Alaska. We hypothesize that warming caused by rising boreal summer insolation drove initial and steady deglaciation from the LGM terminal moraine position until ca. 18 ka, after which time global warming from rising CO2concentrations accelerated retreat. Subsequent periods of moraine deposition in Alaska coincide with decreasing trends in the NGRIP ice core record, at the culmination of Heinrich Stadial 1 (ca. 16–15 ka), and during the early Younger Dryas between 13 and 12.5 ka. While comparisons are made between alpine glacier records and the timing of other geologic events that may have impacted local-to-regional climate (e.g., the opening of the Bering Strait, the saddle collapse between the Laurentide and Cordilleran Ice sheets, and post-LGM Bering Sea dynamics), the relationship between our record and these geologic events are ambiguous. We suggest glaciers across Alaska were possibly more sensitive to other regional and global climate forcing mechanisms, mainly rising insolation, global CO2rise, and Northern Hemisphere Ocean circulation forcing through deglaciation.
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