Abstract
We analyzed the tree-rings δ18O of Abies spectabilis (fir) growing at the subalpine treeline ecotone in the Magguchatti valley. The valley is located in the Indian summer monsoon (ISM) dominated region of western Himalaya and also receives snow precipitation derived by westerly disturbances (WDs) during the winter months. The 60 year developed (1960–2019 CE) tree-ring δ18O chronology revealed a strong positive correlation with the temperature of late winter and spring months (February to April). Strong negative correlations are also apparent for snowcover, soilmoisture, and relative humidity for the same spring season. Our findings partly contrast the significant correlation results of tree-ring δ18O with summer precipitation and drought indices recorded from other summer monsoon-dominated regions in the Himalayas. The spatial correlation analyses with sea surface temperatures (SSTs) and climate parameters showed subdued signals of tropical Pacific at the site, but with a shift to more moisture influx from the Arabian Sea during the last two decades. Moreover, a significant negative correlation with North Atlantic Oscillation further justifies the strongly captured spring temperature and snowcover signals and the weak effect of summer precipitation in fir trees. A temperature rising trend during the latter half of the 20th century and the elevation effect are taken as important factors controlling the moisture source at the treeline ecotone zones.
Highlights
Publisher’s Note: MDPI stays neutralThe Himalayan region, integrated under different domains of the Asian monsoon system [1,2], is climatically highly dynamic
Himalayas are sensitive to temperature, soil moisture, and that trees from the treeline ecotone at subalpine altitudes of the summer monsoon-dominated snowcover of late winter and spring months
Results indicated a collective role of spring western Himalayas are sensitive18to temperature, soil moisture, and snowcover of late winter temperature and snowcover to O fractionation processes in the soil and within trees at and spring months
Summary
The Himalayan region, integrated under different domains of the Asian monsoon system [1,2], is climatically highly dynamic. The region is unique in providing information on the thermal, hydrological, and ecological variability of global relevance. Across the Himalayan region can be unraveled by establishing relationships between different local climate proxy records and climate variables. To assess the dynamics of climate variables on a centennial scale, available instrumental meteorological records are too short and have spatial coverage limitations. Among the archives for retrieving annual to decadal resolved past climatic information for the region, tree-rings are one of the most intensively used climate archives. The global average increase in temperature of around 1.5 ◦ C during the last century is coupled with a subsequent increase in the intensity and duration of heatwaves [9]. The increasing temperature trends with regard to jurisdictional claims in published maps and institutional affiliations
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