Abstract
Accelerated glacier mass loss is primarily attributed to greenhouse-induced warming, but land–climate interaction has increasingly been recognized as an important forcing at the regional-local scale. However, the related effects on the Himalayan glaciers are less explored but believed to be an important factor regulating spatial heterogeneity. This study aims to present a multi-decadal approximation on hydroclimate and glacier interaction over the western central Himalaya (WCH). Three highly coherent, multi-species, tree-ring δ18O site-chronologies from WCH were used to derive regional changes in atmospheric humidity (atmospheric moisture content: AMC) since the last four centuries. Coherency analyses between AMC and glacier mass balance (GMB: tree-ring δ13C-derived) indicate an abrupt phase-shift since the 1960s within a common record of 273 years. To ascertain the cause of phase-shift, annual AMC was disintegrated into seasonal-scale, utilizing δ18O record of deciduous species. Seasonal (winter: October–March; & summer-accumulation season: April–September) decomposition results reveal that winter-westerlies rather than summer precipitation from Indian summer monsoon (ISM) govern the ice-mass variability in WCH. Decadal coherency between summer-season AMC and GMB remained relatively stable since the mid-20th century, despite a decline in central Himalayan summer precipitation (tree-ring δ18O records). We hypothesize that excess water vapor brought to the atmosphere through increase in pre-monsoon precipitation and greening-mediated increase in evapotranspiration might have been recycled through the summer season to compensate for the ISM part of precipitation. However, isotope-enabled ecophysiological models and measurements would be able to strengthen this hypothesis. In addition, high-resolution radiative forcing and glacier valley-scale vegetation trend analyses point towards a probable influence of greening on GMB. Results indicate that attribution of ice-mass to large-scale dynamics is likely to be modulated by local vegetation changes. We contend that glacier-climate models fed with these feedback processes could reliably improve the projections.
Highlights
Glaciers of the Himalaya–Karakoram–Tibetan Plateau (HKT) orogen sustain water resource for the downstream regions as well as it forms a region of perplexing hydroclimatic changes (Bonekamp et al, 2019; Fujita and Nuimura, 2011; Kapnick et 35 al., 2014; Sakai and Fujita, 2017; Wang et al, 2019; Yao et al, 2012, 2019)
This study aims to present a multi-decadal approximation on hydroclimate and glacier interaction over the western central Himalaya (WCH)
Over the HKT, cellulose δ18O chronologies have been extensively utilized to study the spatial climate 215 heterogeneity extending over century to millennium-scale variability in regional hydroclimate, viz. changes in precipitation, atmospheric moisture, cloud cover, vapor pressure, etc., (Grießinger et al, 2017; Huang et al, 2019; Hochreuther et al, 2016; Managave et al, 2019; Sano et al, 2012, 2013, 2017; Singh et al, 2021; Treydte et al, 2006; Xu et al, 2018)
Summary
Glaciers of the Himalaya–Karakoram–Tibetan Plateau (HKT) orogen sustain water resource for the downstream regions as well as it forms a region of perplexing hydroclimatic changes (Bonekamp et al, 2019; Fujita and Nuimura, 2011; Kapnick et 35 al., 2014; Sakai and Fujita, 2017; Wang et al, 2019; Yao et al, 2012, 2019). Recent studies on differential rates of heating and elevation-dependent warming have highlighted the importance of local land–climate interaction and feedback processes in ice-mass variability (Collier et al, 2013; de Kok et al, 2018, 2020; Lau et al, 2010; Mölg et al, 2012b; Pepin et al, 2015; Rashid et al, 2020; Sigdel et al, 2020; Yadav et al, 2019; Yao et al, 2019). We synthesized three coherent tree-ring cellulose δ18O site-chronologies of diverse tree species from different plant functional types, encompassing the last four centuries to derive regional changes in annual
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