Doctor of Philosophy, The Ohio State University, 2017, Environmental Science

The cryosphere is shrinking as a result of climate change. Mountain glaciers, a key component of the cryosphere, serve as headwaters to glacier meltwater streams which support communities of stenothermic organisms. The Tibetan plateau is known as "the Third Pole" for its high number of glaciers, yet very few scientific papers have been published on aquatic invertebrate ecology of glacier-fed streams in the region. On the edges of the Tibetan Plateau in Southeast Tibet's Hengduan mountains, monsoonal temperate glaciers extend well below the treeline as valley glaciers, and are perhaps the most endangered cryosphere-dominated streams in the world due to their low latitudes and altitudes, which makes them sensitive to atmospheric temperature changes. The glaciated headwaters of the Mekong and Yangtze Rivers comprise a small fraction of the annual river discharge, yet at a local scale provide glacial meltwater that supports endemic and potentially rare species. Water temperature and channel stability differ between seasons due to the torrential flow from glacial meltwater during the summer melt season. The Milner & Petts (M&P) model of macroinvertebrate presence in glacier streams was based on the environmental factors of water temperature and channel stability during the summer melt season. In low temperature water close to the glacier, the macroinvertebrate communities are generally limited to Diamesinae chironomids, and further downstream more taxa are found where water temperature and channel stability increase. Therefore, temperature and channel stability are examined as potential limiting factors on the distribution of invertebrate communities, with the goal to compare the insect communities in Southeastern Tibet's glacier-fed streams with the widely-accepted M&P model of invertebrate community structure. Since discharge and hydrology may influence invertebrate distribution in glacier streams, hydraulic characteristics and invertebr (open full item for complete abstract)

Committee: Lanno Lanno Dr. (Advisor); David Denlinger Dr. (Committee Member); Richard Moore Dr. (Committee Member); Donald Dean Dr. (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

Snow and glacial melt were investigated for their dissolved (<0.4µm) 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 im (open full item for complete abstract)

Committee: W. Berry Lyons PhD (Advisor); Anne E. Carey PhD (Committee Member); Andrew G. Fountain PhD (Committee Member); Bryan M. Mark PhD (Committee Member); Lonnie G. Thompson PhD (Committee Member) Subjects: Environmental Science; Geochemistry