The Geochemistry of Supraglacial Streams of Canada Glacier, Taylor Valley (Antarctica), and their Evolution into Proglacial Waters

Abstract

We have investigated the geochemistry of supraglacial streams on the Canada Glacier, Taylor Valley, Antarctica during the 2001-2002 austral summer. Canada Glacier supraglacial streams represent the link between primary precipitation (i.e. glacier snow) and proglacial Lake Hoare. Canada Glacier supraglacial stream geochemistry is intermediate between glacier snow and proglacial stream geochemistry with average concentrations of 49.1 leq L )1 Ca 2+ , 19.9 leq L )1 SO 2À 4 , and 34.3 leq L )1 HCO À 3 . Predominant west to east winds lead to a redistribution of readily soluble salts onto the glacier surface, which is reflected in the geochemistry of the supraglacial streams. Western Canada Glacier supraglacial streams have average SO 2À 4 :HCO À 3 equivalent ratios of 1.0, while eastern supraglacial streams average 0.5, suggesting more sulfate salts reach and dissolve in the western supraglacial streams. A graph of HCO À 3 versus Ca 2+ for western and eastern supraglacial streams had slopes of 0.87 and 0.72, respectively with R 2 values of 0.84 and 0.83. Low concentrations of reactive silicate (>10 lmol L )1 ) in the supraglacial streams suggested that little to no silicate weathering occurred on the glacier surface with the exception of cryoconite holes (1000 lmol L )1 ). Therefore, the major geochemical weathering process occurring in the supraglacial streams is believed to be calcite dissolution.Proglacial stream, Anderson Creek, contains higher concentrations of major ions than supraglacial streams containing 5 times the Ca 2+ and 10 times the SO 2À 4 . Canada Glacier proglacial streams also contain higher concentrations (16.6-30.6 leq L )1 ) of reactive silicate than supraglacial streams. This suggests that the controls on glacier meltwater geochemistry switch from calcite and gypsum dissolution to both salt dissolution and silicate mineral weathering as the glacier meltwater evolves.Our chemical mass balance calculations indicate that of the total discharge into Lake Hoare, the final recipient of Canada Glacier meltwater, 81.9% is from direct glacier runoff and 19.1% is from proglacial Andersen Creek. Although during a typical, low melt ablation season Andersen Creek contributes over 40% of the water added to Lake Hoare, its overall chemical importance is diluted by the direct inputs from Canada Glacier during high flow years. Decadal warming

Solute and isotope geochemistry of subsurface ice melt seeps in Taylor Valley, Antarctica

“…Calcium is greatly enriched relative to Cl -in all the seep waters but not so much as in the glacier melt streams. The primary source of Ca 2+ to the streams is the weathering of Ca-rich alumino-silicates in the hyporheic zones of the streams and the distribution of windblown CaCO 3 (Nezat et al, 2001;Gooseff et al, 2002;Fortner et al, 2005). The low Ca:Cl ratios in the seeps indicate that less chemical weathering occurs in these environments than in the streams.…”

High‐resolution monitoring reveals dissolved oxygen dynamics in an Antarctic cryoconite hole

“…Cryo‐lakes form part of a series of frozen‐topped pool and riffle systems which can modify the phase and concentrations of solutes supplied by ice melt and cryoconite holes. They are a collection zone for meltwaters before they discharge to the proglacial zone via surface and sub‐surface streams (Fountain et al , 2004; Fortner et al , 2005). Both these environments remain ice covered for much of the melt season, apart from during short, discrete, climate warming events when rapid surface melting, which includes the ice lids of cryoconite holes, triggers a transition to ‘open’ system conditions.…”

“…Both these environments remain ice covered for much of the melt season, apart from during short, discrete, climate warming events when rapid surface melting, which includes the ice lids of cryoconite holes, triggers a transition to ‘open’ system conditions. Meltwater volumes, fluxes, and hydrological connectivity increase during this transition (Fortner et al , 2005; Doran et al , 2008). Manual sampling has shown that organic carbon may be generated in cryoconite holes over time as autotrophic micro‐organisms fix carbon dioxide (Bagshaw et al , 2007).…”

Major Ion Geochemistry of Nam Co Lake and its Sources, Tibetan Plateau

“…The relative abundance of TDS experienced a sharp increase during its evolution from the glacier snow to the stream water (Table 1), due to the release of solutes from the stream beds. This is understandable because the relative ionic abundance increases rapidly during its evolution from glacier snow to proglacial water (e.g., Fortner et al 2005). Besides, streams were Table 2 Major ion concentrations in lake water from the Tibetan plateau Lake name Latitude Wang and Dou (1998);d LIZIG (1979); others: Yang et al (2003) mostly sampled in the lower reaches and downstream variations of ionic load generally display an increase trend (e.g., Singh and Hasnain 2002).…”