The geochemistry of glacier snow and melt: The Oregon Cascades and the Taylor Valley, Antarctica.

摘要

Snow and glacial melt were investigated for their dissolved (0.4mum) and environmentally available (unfiltered and acidified 2% HNO3 v/v) elemental concentrations and relation with melt. These studies are presented as three manuscripts. The first manuscript examines geochemical differences between fresh and ablation snow at Eliot Glacier, Mount Hood in the Oregon Cascades. Unlike major ions, environmentally available elements are retained during snowmelt and or added via dry deposition throughout the melt season. Proglacial stream dissolved, or solution chemistry reflects the large degree of processing, primarily weathering and adsorption that occur as water is routed in, through, and beneath the glacier and trace elements bear little relation to their snow concentrations.;The second paper details the importance of aeolian deposition to environmentally available elemental concentrations and distributions in the Taylor Valley, Antarctica. Unlike the Oregon Cascades, there is little precipitation in the Taylor Valley and dry deposition is the dominant source of environmentally available elements. Therefore, proximity to valley floor sediment, wind intensity, wind direction, and glacier surface aspect explain the large degree of chemical heterogeneity between three nearby (10 km) glacier accumulation zones.;Finally the third manuscript explores the controls on dissolved and environmentally available elemental concentrations in supraglacial and proglacial streams in Taylor Valley, Antarctica. This includes identifying the influences of aeolian deposition, hyporheic exchange, and biological uptake on stream geochemistry. Elemental behaviors are examined along with their daily, seasonal, and interannual stream hydrologic conditions. Taylor Valley stream geochemistry is sensitive to landscape aspect as well as to changes in climate including shifts in wind speed and direction, austral summer temperatures, and cloud cover conditions. Decadal 'flood events' are extremely important to Taylor Valley ecosystems as they replenish water and are a source of important trace and minor elements.