Dissolved oxygen variations in alpine glacial meltwaters

Recent models of chemical weathering in alpine glacial meltwaters suggest that sulphide oxidation is a major source of solute in the distributed component of the subglacial hydrological system. This reaction requires O 2 , and may lower dissolved oxygen levels to below saturation with respect to the atmosphere. This should result in an inverse association between SO 7 2‐ and dissolved oxygen saturation. However, measurements of O 2 saturation in bulk meltwaters draining the Haut Glacier d'Arolla, Switzerland, show that there is a positive association between SO 4 2‐ and O 2 saturation. The O 2 content of glacial meltwaters depends on the initial content of snow and icemelt, which may be controlled by the rate of melting, and the kinetic balance between O 2 losses ( e.g. sulphide oxidation, microbial respiration) and gains ( e.g. diffusion of O 2 into solution).