Late Holocene Asian summer monsoon dynamics from small but complex networks of paleoclimate data
Late Holocene Asian summer monsoon dynamics from small but complex networks of paleoclimate data
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DOI：
10.1007/s00382-012-1448-3
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发表时间：
2013-07-01
期刊：
影响因子：
4.6
通讯作者：
Kurths, Juergen
中科院分区：
文献类型：
--
作者：
Rehfeld, Kira;Marwan, Norbert;Kurths, Juergen
亚洲季风系统的内部可变性及其子系统印度和东亚夏季风之间的关系还不足以预测其对未来气候变暖的反应。过去的环境变异性被记录在古气候代理数据中。在亚洲季风区，有许多记录，例如石笋、树轮或沉积岩芯。它们必须在彼此的背景下进行解释，但视觉比较是不够的。不同的增长率导致了时间抽样的不均匀。因此，计算相关值是困难的，因为标准方法需要共同估计观测时间，并且可能会出现依赖于采样的偏差效应。气候网络是从观测到的时间序列中提取系统动力学，并在时空背景下研究地球系统动力学的工具。我们建立了古气候网络来比较空间扩展区域内的古气候记录。我们的方法是基于自适应的线性和非线性关联度量，在存在采样间时间变异性的情况下，它们比基于内插的度量更有效。基于这一新方法，我们研究了全新世晚期亚洲夏季风动力学，重点研究了中世纪暖期(MWP)、小冰期(LIA)和东亚近代变暖时期。在MWP期间，印度夏季风(ISM)对东亚夏季风有较强的影响。在寒冷的LIA期间，ISM环流较弱，并没有向东延伸。最近一段变暖时期产生的网络结果可能表明，目前正在向ISM对中国的更强渗透过渡阶段。我们发现，通过数据的目测比较，我们不可能得出这些结论，并得出结论，古气候网络在研究气候子系统在空间和时间上的变异性方面具有巨大的潜力。
Internal variability of the Asian monsoon system and the relationship amongst its sub-systems, the Indian and East Asian Summer Monsoon, are not sufficiently understood to predict its responses to a future warming climate. Past environmental variability is recorded in Palaeoclimate proxy data. In the Asian monsoon domain many records are available, e.g. from stalagmites, tree-rings or sediment cores. They have to be interpreted in the context of each other, but visual comparison is insufficient. Heterogeneous growth rates lead to uneven temporal sampling. Therefore, computing correlation values is difficult because standard methods require co-eval observation times, and sampling-dependent bias effects may occur. Climate networks are tools to extract system dynamics from observed time series, and to investigate Earth system dynamics in a spatio-temporal context. We establish paleoclimate networks to compare paleoclimate records within a spatially extended domain. Our approach is based on adapted linear and nonlinear association measures that are more efficient than interpolation-based measures in the presence of inter-sampling time variability. Based on this new method we investigate Asian Summer Monsoon dynamics for the late Holocene, focusing on the Medieval Warm Period (MWP), the Little Ice Age (LIA), and the recent period of warming in East Asia. We find a strong Indian Summer Monsoon (ISM) influence on the East Asian Summer Monsoon during the MWP. During the cold LIA, the ISM circulation was weaker and did not extend as far east. The most recent period of warming yields network results that could indicate a currently ongoing transition phase towards a stronger ISM penetration into China. We find that we could not have come to these conclusions using visual comparison of the data and conclude that paleoclimate networks have great potential to study the variability of climate subsystems in space and time.