DISSOLVED TRACE ELEMENT CONCENTRATIONS IN CRYOCONITES AND SUPRAGLACIAL STREAMS, CANADA GLACIER, ANTARCTICA

Antarctica is one of the most geochemically pristine environments on our planet. The analysis of current snow and ancient glacier ice over the past two decades has demonstrated that Antarctic precipitation contains some of the lowest trace element concentrations observed globally. In addition, our recent work has shown that glacial meltwater streams have mean trace metal concentrations that also are very low, especially compared to North American rivers. Here we present data from cryoconites and supraglacial stream waters on the Canada Glacier, Taylor Valley, Antarctica (~78°S). Cryoconites are ice-lidded melt features caused by the introduction of dust onto the glacier surface. Cryoconite may occur in isolation, or be hydrologically connected with supraglacial streams draining off the glacier surface. Cryoconites and supraglacial streams on the western portion of the Canada Glacier have mean dissolved (<0.4 µm) concentrations of Fe, As, Cu, and V of 180, 4.0, 3.2, and 4.1 nM and 104, <0.4, 0.95, and 1.8 nM, respectively. All dissolved Cd concentrations and the vast majority of Pb values are below our analytical detection (i.e. 0.4 and 0.06 nM). Greater hydrologic connection between supraglacial streams and cryoconites homogenizes pH conditions, and creates a narrower range of dissolved concentrations. The dissolved concentrations of all these elements are much lower in nearby proglacial streams draining the Canada Glacier. Additionally, the dissolved concentrations of some of these metals decrease again upon entering the closed-basin lakes that terminate the hydrologic path of this system. A comparison of all the available data indicates that the major source of metals to this aquatic system is from dissolution of dust and other eolian debris within the cryoconites, but dissolved metals are “lost” from solution as water moves through the hydrologic system.