Detection of significant climatic precession variability in early Pleistocene glacial cycles
Detection of significant climatic precession variability in early Pleistocene glacial cycles
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DOI：
10.1016/j.epsl.2020.116137
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发表时间：
2020-04
影响因子：
5.3
通讯作者：
P. Liautaud;D. Hodell;P. Huybers
中科院分区：
文献类型：
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作者：
P. Liautaud;D. Hodell;P. Huybers
尽管对夏季日照有很大的影响，但气候岁差被认为对早更新世冰量和深水温度代理的变化很小。已经提出了各种机制来解释岁差变化的缺乏，包括赤道日射梯度，冰量变化的半球间抵消，以及夏季日照持续时间和强度之间的反相位。我们采用了一种称为经验非线性轨道拟合（ENOF）的方法来估计早更新世代理和他们各自的领先或滞后相对于轨道变化的时间的振幅和岁差强迫。对高分辨率的北大西洋底栖δ 18 O记录（包括IODP站点U1308和U1313的数据）的分析表明，岁差贡献比以前认识到的更大，δ 18 O变化率在3 - 1 Ma之间的平均岁差-岁差振幅比为0.51（0.30-0.76 95%置信区间）。当偏心率超过0.05时，平均值上升到1.18（0.84-1.53）。对早更新世岁差重要性的其他支持来自其估计的振幅与偏心率的协变，对其他海底δ 18 O记录的分析产生了类似的轨道振幅比，以及使用轨道独立的时间尺度也显示了显著的岁差。在整个更新世，与北方半球夏季强度同相的岁差稳步增强，这与晚更新世更常见的岁差一致。一个北方半球冰盖和能量平衡模型运行在早更新世预测轨道振幅与观测结果一致时，冷却相称的北大西洋海面温度施加。这些结果为晚上新世-早更新世气候岁差对冰川作用的影响提供了有力的证据，并与北方半球夏季日照控制冰川作用的假说相一致。
Despite having a large influence on summer insolation, climatic precession is thought to account for little variance in early Pleistocene proxies of ice volume and deep-water temperature. Various mechanisms have been suggested to account for the dearth of precession variability, including meridional insolation gradients, interhemispheric cancellation of ice-volume changes, and antiphasing between the duration and intensity of summer insolation. We employ a method termed Empirical Nonlinear Orbital Fitting (ENOF) to estimate the amplitudes of obliquity and precession forcing in early Pleistocene proxies and their respective leads or lags relative to the timing of orbital variations. Analysis of a high-resolution North Atlantic benthic δ 18 O record, comprising data from IODP sites U1308 and U1313, indicates a larger precession contribution than previously recognized, with an average precession-to-obliquity amplitude ratio of 0.51 (0.30-0.76 95% confidence interval) in the rate-of-change of δ 18 O between 3 and 1 Ma. Averaged when eccentricity exceeds 0.05, this ratio rises to 1.18 (0.84-1.53). Additional support for precession's importance in the early Pleistocene comes from its estimated amplitude covarying with eccentricity, analyses of other benthic δ 18 O records yielding similar orbital amplitude ratios, and use of an orbitally-independent timescale also showing significant precession. Precession in phase with Northern Hemisphere summer intensity steadily intensifies throughout the Pleistocene, in agreement with its more common identification during the late Pleistocene. A Northern Hemisphere ice sheet and energy balance model run over the early Pleistocene predicts orbital amplitudes consistent with observations when a cooling commensurate with North Atlantic sea surface temperatures is imposed. These results provide strong evidence that glaciation is influenced by climatic precession during the late Pliocene and early Pleistocene, and are consistent with hypotheses that glaciation is controlled by Northern Hemisphere summer insolation.