CO2 Consumption Rates in the Glacierized Himalayan Headwaters: the Importance of Sulfuric and Nitric Acid‐Mediated Chemical Weathering Reactions in Geologic Carbon Cycle

Silicate and carbonate weathering reactions consume atmospheric CO2 depending on the type of weathering agents, namely carbonic (H2CO3), sulfuric (H2SO4), and nitric acids (HNO3), and have potential climate implications. However, the importance of HNO3 in weathering processes in the Himalayan glacierized basins has not been examined yet but is critical to better constrain the concomitant short (<10(3) years) and long-term (>10(6) years) variability in the carbon cycle as it can drive negative feedback to a climate. By analyzing time-series hydro-geochemical data of proglacial meltwater in the Ganga headwaters of Central Himalaya, we demonstrate that the weathering rate of carbonate minerals is increased 1.06 times when the role of HNO3 is considered together with H2CO3 and H2SO4 in comparison to the role of H2CO3 and H2SO4. However, we also observe that the CO2 drawdown rate decreases 1.13 times and 1.06 times when the role of all three acids is considered in silicate and carbonate weathering reactions, respectively, compared to the CO2 drawdown rates linked to the role of H2CO3 and H2SO4. Moreover, the involvement of HNO3 in chemical weathering can reduce the inorganic global carbon sink by releasing CO2 into the ocean-atmosphere system. We conclude that HNO3-mediated chemical weathering reactions are important processes that alter the geologic carbon cycle of high-altitude glacierized Himalayan catchments as well as on a global scale.