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

Abstract

ABSTRACT This paper presents new insights into the global carbon cycle related to CO 2 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 CO 2 consumption and solute hydrolysis. The results show that ~90% of the SO 4 2− is derived from crustal sulphide oxidation and ~10% from aerosols and sea salts. However, HCO 3 − 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 CO 2 consumption estimations suggests 10.6 × 10 4 mole km −2 a −1 (19%) through silicate weathering, 15.7 × 10 4 mole km −2 a −1 (28%) through simple hydrolysis, 9.6 × 10 4 mole km −2 a −1 (17%) through SO-CD reaction and 5.9 × 10 4 mole km −2 a −1 (11%) through carbonate carbonation reaction. Our solute provenance calculations clearly indicate that HCO 3 − production and CO 2 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 CO 2 to runoff rather than a sink.