James Headen
SR-Math/Physics-ECSU
[email protected]

ISOTOPIC SIGNATURES OF RAIN AND SNOW IN THE JUNEAU ICEFIELD SNOWPACK
HUGHES, Kelly, Geology Department/Glaciology Group, Portland State College, Portland, OR 97201, [email protected], AMARAL, Tristan, Earth Science, University New Hamsphire, Durham, NH 03824, RAIA, Natalie, Dept Geological Sciences, University Texas, Austin, TX 78712, TAMRE, Erik, Earth and Planetary Science, Harvard, Cambridge, MA 02138, and SMITH, Maya, Computer Information, Winston-Salem State University, Winston-Salem, NC 27110

Climatic shifts in southeast Alaska are likely to result in changing weather patterns across the Juneau Icefield. Glaciers in this region will be threatened by an increase in temperature and frequency of rain events during the accumulation season, undergoing changes that vary based on their elevation and distance from the coast. Rain and snow events affect the glacier snowpack differently, but the possible influence of a changing rain-to-snow ratio has not been investigated on the Juneau Icefield. However, recent mass balance deficits have drawn attention to the importance of changing weather conditions in southeast Alaska. In this study, we will use stable water isotopes (δ18O and δD) to trace the deposition and modification of precipitation during its lifetime in the annual snowpack on the Juneau Icefield. Ice lenses in snow pits dug for mass balance estimates have already been constrained as either resulting from rain events or melt-refreeze cycles, but isotopic analysis of water from these layers provides the high-precision method necessary to determine the relative contribution of each formation process. In addition to comprehension of physical processes occurring within the snowpack in response to different precipitation events, the data collected during this trans-icefield study will contribute to the understanding of trends in isotopic fractionation of precipitation across geographical gradients.

GEODETIC ASSESSMENT OF VOLUME AND SURFACE CHANGE OF THE LEMON CREEK GLACIER BETWEEN 1948 AND 2000
ZINCK, Alexander, Geology, Western Washington University, Bellingham, WA 98225, [email protected], POWELL, Kurt, Environmental Studies, University of Windsor, Windsor, ON N7S 4L3, Canada, and BRIDGERS, Ya'Shonti, Mathematics Department, Elizabeth City State College, Elizabeth City, NC 27909

Mass balance measurements have annually been compiled on the Lemon Creek Glacier since 1953, by the Juneau Icefield Research Program. Several studies used geodetic methods to assess the volume change of Lemon Creek Glacier, however these occur with 40 year time steps. In order to be of significant constraint to long-term mass balance studies, approximately decadal geodetic time steps are needed. This paper describes a compilation of aerial photography, topographic maps, radar topography to create a set of digital elevation models (DEM's) with decadal time steps. The 1957 and 1989 topographic maps of the Lemon Creek Glacier will be geo-referenced to a recent Landsat image and contour lines digitized to create DEM's which complete the existing data. Using DEM differencing the full data set is then examined to yield data regarding volume and surface change on the Lemon Creek Glacier in decadal time steps. Statistics from the volume change evaluation are manipulated to reflect glacier wide mass balance, which can be compared with the existing mass balance ground measurements.