A 1700-year peatland-based hydroclimate record from the Hengduan Mountains in the southeastern Tibetan Plateau reveals changing dynamics of the summer monsoon interface
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引用次数: 0
Abstract
The Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM) affect precipitation patterns across the broad Asian continent. The southern Hengduan Mountains region in the southeastern Tibetan Plateau is located at the ISM–EASM interface, but how these two monsoon systems affect long-term regional precipitation variability remains unclear. Here, we develop a 1700-year record of centennial-scale hydroclimate variability from a rarely reported Sphagnum-dominated subalpine peatland in the southern Hengduan Mountains, using Sphagnum-specific cellulose δ13C and δ18O proxies that are supported by characterization of modern proxy–environment relationships.
Based on the modern variability of cellulose δ13C and δ18O in Sphagnum growth increments, we show that δ13C is a reliable proxy for moisture availability, following the “water film” mechanism. In contrast, δ18O is controlled by multiple mechanisms and can increase due to either higher precipitation δ18O and stronger evaporative enrichment under drier conditions or increased plant use of evaporated pool water caused by pool expansion under wetter conditions. Using the time-varying δ13C–δ18O correlation as a constraint, we infer from our coupled cellulose δ13C–δ18O records several centennial-scale moisture shifts, including wet shifts during 700–1200 CE, 1500–1800 CE, and after 1950 CE, and dry shifts during 300–700 CE, 1200–1500 CE, and 1800–1950 CE, with a generally wetter Medieval Warm Period than the Little Ice Age. The temporal pattern is consistent with previously published regional pollen-climate records but shows disparities from those lake-based terrestrial input records. Based on our novel single-stem isotope analysis, we hypothesize that the latter might be additionally affected by changes in extreme event characteristics.
We find that our new hydroclimate record shows an in-phase relationship with ISM records in the Indian subcontinent, except during 1500–1800 CE and in recent decades, during which our analysis presents evidence for an increased influence from EASM system. We attribute the transitions in large-scale hydroclimate patterns during these two periods to La Niña mean-state and anthropogenic radiative forcing, respectively, which weaken zonal wind flows over the Bay of Bengal—the key passage of the ISM. This study highlights the non-stationary relationship between hydroclimate and Asian summer monsoon dynamics at the ISM–EASM interface.
期刊介绍:
Quaternary Science Reviews caters for all aspects of Quaternary science, and includes, for example, geology, geomorphology, geography, archaeology, soil science, palaeobotany, palaeontology, palaeoclimatology and the full range of applicable dating methods. The dividing line between what constitutes the review paper and one which contains new original data is not easy to establish, so QSR also publishes papers with new data especially if these perform a review function. All the Quaternary sciences are changing rapidly and subject to re-evaluation as the pace of discovery quickens; thus the diverse but comprehensive role of Quaternary Science Reviews keeps readers abreast of the wider issues relating to new developments in the field.