Climatic significance of tree-ring δ18O in the Qilian Mountains, northwestern China and its relationship to atmospheric circulation patterns

A millennium-long tree-ring width chronology for the middle Qilian Mountains in northwestern China has been developed back to A.D. 775. Correlation analysis indicates that the tree-ring width reflects growingseason moisture variability. Our chronology reveals three distinct periods based on the prevailing moisture anomalies: A.D. 775–1101 (wetness persistence), 1101–1831 (dryness persistence) and 1831–2006 (wetness persistence). A 31-year running mean through the tree-ring index series clearly shows seven obvious dry spells and eight wet spells. Compared with the proxies associated with the East Asian monsoon and the westerlies in the past millennium, our moisture-sensitive tree-ring chronology revealed that the East Asian summer monsoon had a strong influence on tree growth before A.D. 1300. From about A.D. 1450–1750, the westerlies strongly affected the Qilian Mountains. After A.D. 1750, a combined influence of both East Asian monsoon and westerlies was apparent. In the past century, the effect of westerlies has become stronger. Our results suggest that tree rings can preserve the information on the advance and retreats of the westerlies and the East Asian summer monsoon. Additionally, this research is helpful for understanding the driving mechanism of the Asian monsoon and the westerlies in northwestern China over the past thousand years.

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Evaluation of Tree Growth Relevant Atmospheric Circulation Patterns for Geopotential Height Field Reconstructions for Asia

Journal of Climate ◽

10.1175/jcli-d-17-0164.1 ◽

2018 ◽

Vol 31 (11) ◽

pp. 4391-4401 ◽

Cited By ~ 4

Author(s):

Andrea Seim ◽

Johannes A. Schultz ◽

Christoph Beck ◽

Achim Bräuning ◽

Paul J. Krusic ◽

...

Keyword(s):

Atmospheric Circulation ◽

Tree Ring ◽

Tree Rings ◽

Tree Growth ◽

Geopotential Height ◽

Large Scale ◽

Weather Conditions ◽

Atmospheric Circulation Patterns ◽

Circulation Patterns ◽

Height Fields

Atmospheric circulations influence local and regional weather conditions and, thus, tree growth. To identify summer weather types relevant for tree growth, and their associated synoptic-scale circulation patterns, an atmospheric circulation tree ring index (ACTI) dataset, derived from 414 tree-ring sites across Asia spanning the period 1871–2010, was created. Modes of common variability in the ACTI dataset were compared with leading modes of observed summertime 500-hPa geopotential height. The first four ACTI modes (explaining 88% of the total variance) were associated with pressure centers over Eurasia, the tropics, and the Pacific Ocean. The high spatiotemporal resemblance between the leading circulation modes, derived from both tree rings and 500-hPa geopotential height fields, indicates a strong potential for reconstructing large-scale circulation patterns from tree rings in Asia. This would allow investigations of natural atmospheric circulation variability prior to anthropogenic climate change and provide a means to validate model simulations of climate predictions.

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