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<p>Understanding of chemical weathering process involved in ionic elution helps in distinguishing the CO<sub>2</sub> sequestration rate at the different micro-climatic setup of Himalayan catchments. In the present study, we have selected three glaciated basins from two different climatic zones of Western Himalayas (Lato and Phutse from the cold-arid zone of Ladakh and Chhota Shigri from the monsoon-arid zone of Himachal Pradesh, India) for determining various solute sources, CO<sub>2</sub> sequestration rate and its control over melt-water quality. Solute sourcing models used in this work shows major cations like Ca<sup>2+</sup>  and Mg<sup>2+ </sup>are from crustal rock-weathering while Na<sup>+</sup> and K<sup>+</sup> sourced out from the sea-salt origin. However, major anions like SO<sub>4</sub><sup>2-</sup> (> 85%) were derived from the crustal origin and HCO<sub>3</sub><sup>-</sup> mostly derived from atmospheric sources (39% to 45 %) in all catchments except HCO<sub>3</sub><sup>-</sup> contribution from carbonation dissolution and silicate weathering is ~29% and ~16% for Ladakh catchments compared to ~9 % and ~29% in Chhota Shigri respectively. The solute model also reveals that the contribution of sulphate oxidative mediated carbonate dissolution (SOCD) in HCO<sub>3</sub><sup>-</sup> flux is relatively higher in Chhota Shigri (~16%) than others (~9%). It is also observed that catchment like Chhota Shigri having a combined network of channelized and distributed drainage patterns with lower specific discharge, more glacierized area, low pH, high pCO<sub>2</sub>, Low molar ratio [Ca<sup>2+</sup> + Mg<sup>2+</sup>]/[ Na<sup>+</sup> + K<sup>+</sup>], high SMF (~ 0.4), low CO<sub>2 carbonate</sub>/CO<sub>2 silicate</sub> ratio (~1.3) show relatively more sulphide oxidative and silicate weathered products than other catchments. Conversely, presence of excess non-glaciated areas in Stok and Phutse having well-channelized subsurface discharge with high CO<sub>2 carbonate</sub>/CO<sub>2 silicate </sub>ratio (~10 to ~5) show enhanced carbonation via atmospheric CO<sub>2</sub> (CAC) and carbonate dissolution with high annual CO<sub>2</sub> sequestration. Thus, varying subglacial drainage system, specific discharge pattern and reactive rock-types with distinct hydro-micro-climatic set up alters the chemical weathering mechanism in these catchments and control meltwater quality.</p>

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The present meteorological study has been carried out on the Chhota Shigri glacier during the study period from 1 October 2013 to 30 September 2014 (one hydrological year). The annual mean temperature over the surface of glacier was recorded to be -6.0 °C during the study period. This study shows that the hydrological year 2013/2014 was relatively colder as compared to the hydrological years 2009/10, 2010/11 and 2012/13 in the Chhota Shigri glacier. Maximum relative humidity (RH) in the study area was reported in the summer-monsoon season, whereas minimum relative humidity was observed in the post-monsoon season. On the other hand, highest mean seasonal incoming shortwave (SWI) radiation over the surface of Chhota Shigri glacier was found in the pre-monsoon season, whereas lowest SWI radiation was observed in the winter season. The annual mean incoming longwave (LWI) radiation and outgoing longwave (LWout) radiation in the investigation area were calculated to be 227 and 293 Wm -2 , respectively and the annual mean wind speed was computed to be 4.0 ms -1 during the hydrological year 2013/14. Wind regime of the study area plays a significant role in the transportation of moisture and melting of glacier. Wind rose diagram shows that wind blew from south to south-west direction during most of the time period at the Chhota Shigri glacier.