Long-term Studies of Tidewater and Terrestrial Dynamics, Glacier Hydrology and Holocene and Historic Climate Activity, Glacier Bay National Park and Preserve, southeast Alaska

Lawson, Daniel; Finnegan, David; Kopcynski, Sarah; Bigl, Susan

Understanding tidewater and terrestrial glacial and glacial-marine environments is critical to determining the long term impacts that contemporary climate changes and anthropogenic activities may have on terrestrial and marine ecosystems in the Park. This understanding can only be acquired through long-term, repetitive and quantitative analyses of regional and global factors including climate, hydrology, oceanography and geophysical processes and their role in the physical proc-essses of glacial and glacial-marine environments. We conduct repetitive hydrologic and oceanographic measurements in-glaciers and fjords that reveal seasonal, annual and longer-term trends, as well as define rates of erosion, sedimentation and sediment flux. Climatic investigations include analyzing modern meteorological trends at 26 locations across Glacier Bay and measuring the isotopic composition (äO, äD) of precipitation, surface water and glacier ice to assess regional hydro-logic trends. These data are improving our understanding of the regional variability in the hydrologic cycle and localized weather patterns, allowing us to examine how the current climate affects glacier activity and mass balance. Concurrently, the Park's longer-term Holocene glacial history and paleoclimate are being investigated using dendrochronological and radio-carbon dating of in-situ stumps, logs and soils. We have precisely located samples of over 100 interstadial stumps and bur-ied logs that were overridden by ice moving down-fjords during several advances in the Holocene. Radiocarbon dating by Accelerated Mass Spectrometry (AMS) has provided a preliminary estimate of ice-marginal positions and probable rates of advance of tidewater glaciers during four advances over the last 12000 yrs BP. We are also attempting to develop a tree-ring chronology spanning the last 9,000 years on cross sections of these trees. If successful, this would be the only such dataset for a subarctic region in Alaska and the North Pacific region, and would provide data critical to calibrating Global Climate Models (GCM's) to predict future changes in climate. We will be intensifying our efforts to better understand the Little Ice Age climate and glacial history and the Tlingit legends of catastrophic glacial advance and flooding during that time.