Models of landscape evolution in the face of repeated glaciation incorporate assumptions about glacial sliding that are in need of field verification. Temperate glaciers slide when water pressures are high. As primary subglacial erosion mechanisms are attributable to sliding of the glacier over its bed, the spatial and temporal pattern of sliding, and of the subglacial drainage network that control it, are important to understand. The proposed research acts upon hypotheses generated in two recently completed NSF-supported grants in which 1) the sliding field on the small Alaskan Bench glacier was carefully documented using continuous differential GPS, reaching its maximum speed at times of highest water storage within the glacier, and 2) the annual outburst flood of Hidden Creek Lake beside the much larger Kennicott glacier was shown to greatly perturb the hydrologic system. The 400 m thickness of the Kennicott Glacier allows much more rapid collapse of the subglacial drainage network than on the 150 m thick Bench Glacier during times of low snowmelt input to the glacier surface. As the snowmelt input increases again, the subglacial plumbing system must re-grow, during which time it should re-pressurize, promoting another period of sliding. If this is the case, then glacial thickness emerges as a primary control on the total annual sliding of a glacier, and therefore on the ability of a glacier to erode the landscape. The proposed research takes advantage of the accessibility and size of this Kennicott Glacier to investigate in detail the sliding history of this large temperate glacier and its association with both the seasonally-evolving water storage and pressure fields, and the inevitable annual Hidden Creek outburst flood. In this pilot project, the following hypotheses will be tested, in the hope that the data generated will serve as proof that the work is both tractable and productive of insight into the system. * Short-lived sliding increases will occur during ice dammed lake outbursts. * Sliding anomalies at the Kennicott Glacier occur in association with synoptic variations in melt inputs. * Long, thick glaciers, like the Kennicott glacier, will experience both more total sliding than thin glaciers, and multiple sliding events within a single melt season. The data to be collected include time series of: glacier surface motion, using multiple GPS receivers on the glacier run in differential continuous mode; water inputs by snowmelt and outputs from the exit river to constrain evolution of the water balance; englacial water pressures at several locations along the subglacial flood route that take advantage of side-glacier lakes and moulins; water chemistry at the outlet stream. Taken together, this data will directly test an existing model of linked glacial dynamics and subglacial network evolution. Broader Impact. As the research will be accomplished near the Wrangell St Elias National Park's primary entrance near McCarthy, the research on the Kennicott Glacier is ideally situated to allow direct communication of both our scientific methods and results to the public. As in prior work, public talks will be given to national park visitors in formal seminars. Activities will be coordinated with the Wrangell Mountains Center, a private non-profit institute dedicated to education and research, through their Alaska Wildlands Studies, a 7-week field course accredited for college students through UC Santa Barbara. Guest lectures on principles and field techniques of glaciology and glacial geology will be given, and opportunities for involvement of its these students in the field work will be offered. The research will employ and train one Ph.D. student from CU, and at two undergraduate students.
