Abstract
Here we present a synthesis of the trace element chemistry in melt on the surface Canada Glacier, Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica (~78°S). The MDV is largely ice-free. Low accumulation rates, strong winds, and proximity to the valley floor make these glaciers dusty in comparison to their inland counterparts. This study examines both supraglacial melt streams and cryoconite holes. Supraglacial streams on the lower Canada Glacier have median dissolved (<0.4 µm) concentrations of Fe, Mn, As, Cu, and V of 71.5, 75.5, 3.7, 4.6, and 4.3 nM. All dissolved Cd concentrations and the vast majority of Pb values are below our analytical detection (i.e. 0.4 and 0.06 nM). Chemical behavior did not follow similar trends for eastern and western draining waters. Heterogeneity likely reflects distinctions eolian deposition, rock:water ratios, and hydrologic connectivity. Future increases in wind-delivered sediment will likely drive dynamic responses in melt chemistry. For elements above detection limits, dissolved concentrations in glacier surface melt are within an order of magnitude of concentrations observed in proglacial streams (i.e. flowing on the valley floor). This suggests that glacier surfaces are an important source of downstream chemistry. The Fe enrichment of cryoconite water relative to N, P, or Si exceeds enrichment observed in marine phytoplankton. This suggests that the glacier surface is an important source of Fe to downstream ecosystems.
Highlights
Cryoconite holes are small, water-filled holes formed on the surface of glacier ice by the deposition and accumulation of eolian material (Fountain et al, 2008)
We examine the fate of this dissolved fraction as it is transported from supraglacial environments to the proglacial stream environment, and into its terminal path, the closedbasin lakes
Low cryconite hole sample numbers limit our interpretation of dynamics, but they are still offer a first examination of trace elements in these systems
Summary
Cryoconite holes are small, water-filled holes formed on the surface of glacier ice by the deposition and accumulation of eolian material (Fountain et al, 2008). Cryoconite holes on polar glaciers have frozen lids that minimize contact with the atmosphere (Bagshaw et al, 2013). Cryoconite holes increase their interconnectivity and form supraglacial streams (Fountain et al, 2008). Streams typically include a series of ice-covered pool and riffle sequences of varying size and dimensions that can fill and drain rapidly during the ablation season (Fountain et al, 2004; Bagshaw et al, 2007; Tranter et al, 2010). Glacier surface melt contribute most of the downstream because MDV glacier have frozen beds (Fountain et al, 2004; Tranter et al, 2010)
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