The chemical composition of runoff from Canada Glacier, Antarctica: Implications for glacier hydrology during a cool summer

Abstract

Variations in the chemical composition of subsurface runoff within Canada Glacier, Antarctica, are used to identify the main source waters, which are vertical surfaces, and melt from solar-heated debris within channels, cryoconite holes and pools. The main flow paths are subsurface connections between cryoconite holes, pools and riffles. The latter may become partially disconnected during hard freeze. The chemical composition of runoff at the outlet of Canada Glacier during January 2000 was dominated by Ca2+, HCO3- and sea salt (Na+ and Cl-), and became depleted in sea-salt and non-sea-salt* SO42- as the subsurface drainage system in a frozen pool-and-riffle system was flushed and the melting ice surface became depleted of overwinter dry deposited salts. only during 2 days of hard freeze did sea salt and *SO42- increase in concentration together. Otherwise, sea salt and *SO42- declined while *Ca2+ and HCO3- increased. The latter ions are derived from the chemical weathering of sediment in frozen-topped pools, channels and cryoconite holes. It is inferred that the hydrochemical processes which occur in the vestigial, subsurface drainage system are the elution of ions from ice melt, dilution of these ions downstream by ice melt from vertical surfaces and the dissolution of dust, in subsurface pools, channels and/or cryoconite holes.