Using Holo-Hilbert spectral analysis to quantify the modulation of Dansgaard-Oeschger events by obliquity
Using Holo-Hilbert spectral analysis to quantify the modulation of Dansgaard-Oeschger events by obliquity
复制标题
使用 Holo-Hilbert 谱分析来量化 Dansgaard-Oeschger 事件的倾斜调制
DOI：
10.1016/j.quascirev.2018.05.019
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发表时间：
2018-07-15
影响因子：
4
通讯作者：
Qiao, Fangli
中科院分区：
文献类型：
--
作者：
Deng, Jia;Wu, Zhaohua;Qiao, Fangli
天文强迫（岁差和岁差）被认为是调制Dansgaard-Oeschger（DO）事件，但这种调制的详细量化还没有被检查。在这项研究中，我们应用新的全息希尔伯特谱分析（HHSA）的五个极地冰芯记录，量化天文强迫的时变幅度调制的DO事件，并确定大幅度调制的首选相位。HHSA的独特优势，在广泛使用的窗口傅立叶谱分析量化天文强迫的非线性调制的DO事件首次证明了与合成数据，非常类似的DO事件记录在格陵兰冰芯（NGRIP，GRIP，GISP 2核心GICC 05 modelext时标）。对古气候代用指标的分析表明，在格陵兰地区，DO事件发生的频率明显高于其它地区，且DO事件的振幅调制较大，这一现象往往发生在盐度的下降阶段，尤其是从平均值到最小值的阶段。在东南极，尽管在统计上有显著意义的是，一般情况下，DO事件更多地发生在盐度下降阶段，但盐度对DO事件的大幅度调制的优先相位是盐度最大值附近的一段增加阶段，这意味着两个极区的DO事件的物理机制可能不同。此外，通过交叉谱和星等平方分析，格陵兰溶解氧模态在约1400年的时间尺度上领先于南极溶解氧模态在同一时间尺度上约1000年。(C)2018爱思唯尔有限公司版权所有。
Astronomical forcing (obliquity and precession) has been thought to modulate Dansgaard-Oeschger (DO) events, yet the detailed quantification of such modulations has not been examined. In this study, we apply the novel Holo-Hilbert Spectral Analysis (HHSA) to five polar ice core records, quantifying astronomical forcing's time-varying amplitude modulation of DO events and identifying the preferred obliquity phases for large amplitude modulations. The unique advantages of HHSA over the widely used windowed Fourier spectral analysis for quantifying astronomical forcing's nonlinear modulations of DO events is first demonstrated with a synthetic data that closely resembles DO events recorded in Greenland ice cores (NGRIP, GRIP, and GISP2 cores on GICC05 modelext timescale). The analysis of paleoclimatic proxies show that statistically significantly more frequent DO events, with larger amplitude modulation in the Greenland region, tend to occur in the decreasing phase of obliquity, especially from its mean value to its minimum value. In the eastern Antarctic, although statistically significantly more DO events tend to occur in the decreasing obliquity phase in general, the preferred phase of obliquity for large amplitude modulation on DO events is a segment of the increasing phase near the maximum obliquity, implying that the physical mechanisms of DO events may be different for the two polar regions. Additionally, by using cross-spectrum and magnitude-squared analyses, Greenland DO mode at a timescale of about 1400 years leads the Antarctic DO mode at the same timescale by about 1000 years. (C) 2018 Elsevier Ltd. All rights reserved.