Carbonate and silicate weathering in glacial environments and its relation to atmospheric CO₂ cycling in the Himalaya

Abstract

This paper presents new insights into the global carbon cycle related to CO2 consumption from chemical denudation in heavily glacierised Himalayan catchments. Data from previous studies of solute concentrations from glacierised catchments were reprocessed to determine the regional scale of CO2 consumption and solute hydrolysis. The results show that ~90% of the SO42− is derived from crustal sulphide oxidation and ~10% from aerosols and sea salts. However, HCO3− flux calculation estimates contribution from sulphide oxidation to carbonate dissolution (SO-CD) (~21%), similar to the contributions from silicate dissolution and simple hydrolysis (~21 and ~20%, respectively). Furthermore, the atmospheric CO2 consumption estimations suggests 10.6 × 104 mole km−2 a−1 (19%) through silicate weathering, 15.7 × 104 mole km−2 a−1 (28%) through simple hydrolysis, 9.6 × 104 mole km−2 a−1 (17%) through SO-CD reaction and 5.9 × 104 mole km−2 a−1 (11%) through carbonate carbonation reaction. Our solute provenance calculations clearly indicate that HCO3− production and CO2 consumption via silicate weathering reactions is balanced by the simple hydrolysis and coupled SO-CD process. This shows a counter mechanism operating in subglacial environments of the Himalaya as a source of CO2 to runoff rather than a sink.

Chemical weathering and CO2 consumption in the glaciated Karuxung River catchment, Tibetan Plateau

“…Moreover, the contribution of carbonate weathering dominated most of the ionic concentrations in the QYG meltwater runoff (58%) and stream water at the WGHS (51%) and LE (43%); the sulfate mostly resulted from sulfide oxidation played a secondary role in the QYG meltwater runoff solute (35%) and stream water solute at the WGHS (42%) and LE (30%) (Table 3). The similar inference has been drawn by the studies carried out in the glacial environments in some other areas (Anderson et al, 1997;Colombo et al, 2019;Hindshaw et al, 2016;Shukla et al, 2018;Stachnik et al, 2016;Torres et al, 2014;Xu & Liu, 2007). For example, Shukla et al (2018) examined the chemical weathering in the Himalayan glacial environments where $90% of the SO 4 2À is derived from crustal sulfide oxidation; and Li, Ding, Liu, et al (2019) examined the chemical weathering in a Southeastern Tibetan Plateau glacier meltwater dominated catchment, where HCO 3 À and Ca 2+ in the meltwater and river water primarily come from calcite weathering, and SO 4 2À is mainly derived from pyrite oxidation.…”

“…The similar inference has been drawn by the studies carried out in the glacial environments in some other areas (Anderson et al, 1997;Colombo et al, 2019;Hindshaw et al, 2016;Shukla et al, 2018;Stachnik et al, 2016;Torres et al, 2014;Xu & Liu, 2007). For example, Shukla et al (2018) examined the chemical weathering in the Himalayan glacial environments where $90% of the SO 4 2À is derived from crustal sulfide oxidation; and Li, Ding, Liu, et al (2019) examined the chemical weathering in a Southeastern Tibetan Plateau glacier meltwater dominated catchment, where HCO 3 À and Ca 2+ in the meltwater and river water primarily come from calcite weathering, and SO 4 2À is mainly derived from pyrite oxidation. These results similar to those in this study illustrated that with pyrite as the most common sulfide mineral and SO 4 2À mainly resulted from pyrite oxidation, carbonate weathering and sulfide oxidation driven by enhanced weathering of freshly exposed rocks could be the dominant reactions in the subglacial environments.…”

Prediction of the calcium carbonate budget in a sedimentary basin: A “source‐to‐sink” approach applied to Great Salt Lake, Utah, USA

“…As it consumes CO 2 , the quantification of weathering processes of silicates and carbonates has become crucial in the actual context of climate change (e.g. Liu, Dreybrodt, & Liu, ; Romero‐Mujalli, Hartmann, & Börker, ; Shukla, Sundriyal, Stachnik, & Mehta, ). The (re)mobilized calcium is transported by the different fluids: the air (e.g.…”

Limited Carbon Cycle Response to Increased Sulfide Weathering Due to Oxygen Feedback

“…Volcanism and metamorphic outgassing are typically considered the main sources of to the long‐term carbon cycle. However, recent attention has been drawn to the source associated with sulfuric acid produced by sulfide mineral weathering (e.g., pyrite) dissolving carbonate rocks (Blattmann et al., 2019; Emberson et al., 2018; Kölling et al., 2019; Shukla et al., 2018; Spence & Telmer, 2005; Torres et al., 2014, 2017). The sulfide oxidation flux has been reestimated at higher values than previously thought (Burke et al., 2018; Calmels et al., 2007) and is correlated to erosion rate (Bufe et al., 2021; Calmels et al., 2007; Hilton & West, 2020; Torres et al., 2016, 2017).…”