The Dome Fuji ice core DF2021 chronology (0–207 kyr BP)
The Dome Fuji ice core DF2021 chronology (0–207 kyr BP)
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DOI：
10.1016/j.quascirev.2022.107754
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发表时间：
2022-10
影响因子：
4
通讯作者：
Ikumi Oyabu;K. Kawamura;C. Buizert;F. Parrenin;A. Orsi;Kyotaro Kitamura;S. Aoki;T. Nakazawa
中科院分区：
文献类型：
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作者：
Ikumi Oyabu;K. Kawamura;C. Buizert;F. Parrenin;A. Orsi;Kyotaro Kitamura;S. Aoki;T. Nakazawa
精确的冰芯年表对于确定极地气候变化的时间和持续时间以及它们与地球仪其他地区变化的阶段至关重要。然而，现有的冰芯年表超过过去60 kyr表现出相对较大的分歧，彼此之间，并与U-Th年代的洞穴。在这里，我们通过结合贝叶斯定年模型和积雪致密化模型，在各种类型的年代学和冰川学信息的约束下，包括新的δO2/N2年龄标志，精确同步到其他高质量的年代学，构建了富士圆顶（DF）核心（DF 2021）在过去207 kyr的新的冰和气体年龄标度（火山、宇宙成因和CH 4信号），以及N2的高分辨率δ 15 N（反映过去的积雪厚度）。新的年表严格地受到与过去60 kyr的其他日期明确的记录同步的限制，而它独立于旧时期的其他年表。在过去的60 kyr，DF 2021年表同意层计数冰芯年表（GICC 05和WD 2014的一部分）和U-Th年代的洞穴沉积物在1200年内。在60-130 kyr BP期间，DF 2021年所有Dansgaard-Oeschger变暖事件的时间与U-Th定年的中国或欧洲洞穴沉积物中相应事件的时间基本一致，大多在1 kyr内（在DF 2021的2σ不确定度内）。这一良好的一致性表明我们的年代学具有很高的准确性，并支持过去当地夏至日射与气泡闭合时δO2/N2分馏之间的相位可以忽略的假设（这是构建δO2/N2年龄标志的基础）。在130 - 207 kyr BP（倒数第二次冰期）之间，大气CH 4和洞穴沉积物方解石δ 18 O变化之间的相似性程度低于末次冰期，这使得年龄比较具有挑战性。将DF 2021与7个突变事件的9个U-Th年龄进行比较，结果显示平均差异为−0.2 ± 0.8 kyr，这在DF 2021的不确定性范围内（大约1.5 kyr）。DF 2021年表与AICC 2012年表一致，在2 kyr内，除了在103 kyr BP和128 kyr BP之间，AICC 2012可能太年轻，最多为14 kyr。通过分析DF 2021年的O2 δ 18 O（δ 18 Oatm）与65°N夏至日射的滞后性，发现AICC 2012年的较大误差来源于3个δ 18 Oatm标志点，这3个标志点的误差均大于3 kyr。在这项研究中确定的δ18大气和轨道强迫之间的相位可能对未来的冰芯测年有用，特别是在其他年龄限制较弱或缺乏的情况下。
Precise ice-core chronologies are essential for identifying the timing and duration of polar climatic changes as well as their phasing with the changes in other parts of the globe. However, existing ice-core chronologies beyond the last 60 kyr show relatively large disagreements with each other and with U–Th chronologies of speleothems. Here, we constructed new ice and gas age scales for the Dome Fuji (DF) core (DF2021) over the last 207 kyr by combining a Bayesian dating model and firn densification model, constrained by various types of chronological and glaciological information including new δO2/N2age markers, precise synchronization to other high-quality chronologies (volcanic, cosmogenic, and CH4signals), and high-resolution δ15N of N2(reflecting past firn thickness). The new chronology is tightly constrained by synchronization to other well-dated records for the last 60 kyr, whereas it is independent from other chronologies for the older period. For the last 60 kyr, the DF2021 chronology agrees with the layer-counted ice core chronologies (GICC05 and a part of WD2014) and U–Th chronologies of speleothems within ∼200 years. For the period 60–130 kyr BP, the timing of all Dansgaard-Oeschger warming events on DF2021 agree with those of corresponding events in the U–Th dated Chinese or European speleothems mostly within 1 kyr (well within 2σ uncertainty of DF2021). The excellent agreement suggests high accuracy of our chronology, and supports the assumption of negligible phasing between the past local summer solstice insolation and δO2/N2fractionation at bubble close-off (the basis for constructing the δO2/N2age markers). Between 130 and 207 kyr BP (penultimate glacial period), there is a lower degree of similarity between the variations in atmospheric CH4and speleothem calcite δ18O than in the last glacial period, making the age comparison challenging. The comparison of DF2021 with 9 U–Th dates at 7 abrupt events shows the mean difference of −0.2 ± 0.8 kyr, which is within the DF2021 uncertainty (on the order of 1.5 kyr). The DF2021 chronology agrees with the AICC2012 chronology within 2 kyr except between ∼103 and 128 kyr BP where AICC2012 is likely too young by up to ∼4 kyr. By analyzing the lag between δ18O of O2(δ18Oatm) on DF2021 and 65°N summer solstice insolation, the relatively large error in AICC2012 is found to originate in three δ18Oatmage markers assuming a constant lag, which are off by more than 3 kyr. The phasing between δ18Οatmand orbital forcing identified in this study may be useful for future ice core dating, especially where other age constraints are weak or lacking.