Chemical weathering and solute export by meltwater in a maritime Antarctic glacier basin

• Published in: Biogeochemistry
• Main Authors: Hodson, Andy, Heaton, Tim, Langford, Harry, Newsham, Kevin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2010
• Subjects: Antarctic; Tuva; Antarc*; Cold-based glacier
• Online Access: http://nora.nerc.ac.uk/id/eprint/9800/; https://nora.nerc.ac.uk/id/eprint/9800/1/Biogeochem_in_revision.pdf; http://www.springerlink.com/content/100244/

Solute yields, laboratory dissolution data and both chemical and isotopic markers of rock weathering reactions are used to characterise the biogeochemistry of glacial meltwaters draining a maritime Antarctic glacier. We find that delayed flowpaths through ice-marginal talus and moraine sediments are critical for the acquisition of solute from rock minerals because delayed flowpaths through subglacial sediments are absent beneath this small, cold-based glacier. Here the mechanisms of weathering are similar to those reported in subglacial environments, and include sub-oxic conditions in the early summer and increasingly oxic conditions thereafter. Up to 85% of the NO3 − and 65% of the SO4 2− are most likely produced by bacterially mediated reactions in these ice marginal sediments. However, reactive pyrite phases are sparse in the host rocks, limiting the export of Fe, SO4 2− and cations that may be removed by weathering once pyrite oxidation has taken place. This means that dissolution of Ca2+ and Na+ from carbonate and silicate minerals dominate, producing moderate cationic denudation yields from Tuva Glacier (163 Σ*meq+ m−2 a−1) compared to a global range of values (94–4,200 Σ*meq+ km−2 a−1). Overall, crustally derived cations represent 42% of the total cationic flux, the rest being accounted for by snowpack sources.