Abstract
The South Asian Monsoon and mid-latitude Westerlies are two important controls on Tibetan Plateau (TP) fresh water resources. Understanding their interaction requires long-term information on spatial patterns in moisture variability on the TP. Here we develop a network of 23 moisture-sensitive tree-ring chronologies from major juniper forests in a north–south transect on the eastern TP. Over the past five and a half centuries, we find that these chronologies cluster into two groups, North and South, of ∼33° N. Southern and northern regional chronology subsets are positively and significantly correlated with May–June Palmer Drought Severity Indices (PDSI). The meridional moisture stress gradient reconstructed from these data suggests substantial stochastic variation, yet persistent moisture stress differences are observed between 1463–1502 CE and 1693–1734 CE. Identification of these patterns provides clues linking them with forced or intrinsic tropical–extratropical interactions and thus facilitates studies of interannual–decadal dipole variations in hydroclimate over the TP.
Highlights
The South Asian Monsoon and mid-latitude Westerlies are two important controls on Tibetan Plateau (TP) fresh water resources
Our records may provide further basis for mechanistic understanding of the response of the Tibetan Plateau moisture delivery to changes in external radiative climate forcing within these two periods, and for validating the statistics of the intrinsic variations in Tibetan Plateau moisture conditions as represented in climate models[14,20]
Our study significantly increases the number of chronologies and spatial coverage across the eastern Tibetan Plateau, for the southern region where old-growth forests are located in remote and hard-to-access areas
Summary
The South Asian Monsoon and mid-latitude Westerlies are two important controls on Tibetan Plateau (TP) fresh water resources. Examination of paleoclimate records of ice cores, speleothems and lake sediments with quinquennial to millennial-scale observational resolution and chronological control have shown a broad pattern of inferred moisture variations and related interplay between tropical and extratropical moisture sources[11,12,13] Further understanding of these tropical–extratropical interactions requires independent, annually resolved estimates of warm season Tibetan Plateau moisture variability on both the southern and the northern Tibetan Plateau to fill the gaps between the short but highly resolved instrumental records and the coarser resolution paleoclimatic observations, so that the projected anthropogenic forced variation[14] can be placed into the context of the unforced and intrinsic variations on decadal to centennial timescales[15]. Our records may provide further basis for mechanistic understanding of the response of the Tibetan Plateau moisture delivery to changes in external radiative climate forcing within these two periods, and for validating the statistics of the intrinsic variations in Tibetan Plateau moisture conditions as represented in climate models[14,20]
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