Ice cores from ice sheets and high altitude locations provide some of the most detailed records of past climate. To reconstruct the climate history of the North Pacific, a collaborative Japanese-Alaskan ice core drilling project has been started. Japanese researchers from Hokkaido University drilled a shallow (50 m) core in the Wrangell caldera and plan to drill a 300m core in 2004. In addition, flow modeling will be done which is instrumental to help date the core, establish the origin of the ice, and calculate historic accumulation rates. Seismic and radio echo sounding methods will be used to define the geometry of the caldera. The ice flow velocity will be measured with the GPS method at a stake network, and the same stakes will be used to establish the spatial distribution of accumulation rates. These measurements allow a calculation of the caldera's mass balance and, therefore, the basal melt rates due to volcanic heat fluxes. The rheological properties of the firn will be constrained by borehole closure and firn compaction measurements. Temperatures in the borehole will also be monitored. This information will serve as input or test data of a thermo-mechanical finite element model that will be used to interpret the ice core.
INTELLECTUAL MERIT; The Principal Investigators will use field measurements of geometry, present-day flow and accumulation distribution, and rheological firn properties to constrain a time-dependent thermo-mechanical flow model of the Wrangell caldera. This model will be used to interpret the 300m core and deduce the accumulation history. The accumulation data will be compared to those from Ushkovsky volcano in Kamchatka. The setting is similar to Mt. Wrangell, and the Ushkovsky caldera is located at a similar latitude and altitude on the eastern side of the Pacific Ocean. There, accumulation rates have been observed to be anti-correlated to the Pacific Decadal Oscillation (PDO). This study will fill a gap in the study of the climate history of the North Pacific.
BROADER IMPACTS: Mount Wrangell is an excellent study area for interdisciplinary sciences. The study will be of interest to meteorologists, because the Wrangell Mountains form a major barrier to Pacific storm tracks, sheltering Alaska's interior. Climatologists will be interested in the accumulation history, its relation to that of Kamchatka and to the PDO. The use of the caldera ice as a calorimeter to deduce geothermal heat flow will be of interest to volcanologists, and the results will be compared to a funded project of measuring melt in the North Crater. The study will take place within the boundaries of Wrangell St. Elias National Park. The research will form the basis of a PhD thesis. This project establishes a collaboration with researchers of the Low Temperature Institute in Sapporo, Japan, who will drill and analyze the ice core. For the study and modeling of the firn rheology, a collaboration exists with VAW, ETH Zurich, Switzerland. Results of the study will be published in peer-reviewed journals and reported at national and international meetings.
