Ice Core Reconstruction of North Pacific Climate Variability and Environmental History from the Bona-Churchill Ice Field, Alaska

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AbstractOPP- 00-99311ThompsonThe Principal Investigators will retrieve ice cores from the col between Mt. Bona and Mt. Churchill, located in Wrangell Mountains, southeastern Alaska. The ice core records will fill a significant void in the high resolution climate history of this region and will complement and extend the tree ring-based climate records. These records will be an important contribution to the suite of high resolution ice core histories from other north polar ice fields including, Greenland, Svalbard, the High Canadian Arctic the Windy Dome Ice Cap (Franz Josef Land, Russian Arctic) and Greenland. These polar records are part of a global suite of ice core records including those retrieved from seven lower latitude, high altitude sites in Tibet, South America, and Africa. These cores have contributed critical low-latitude proxy climate histories to the continuing efforts to identify the major drivers of Quaternary climate change and to determine the global synchronicity of glacial-age climate events. Currently, there are no high quality ice core records from Alaska, so these cores should provide critical new insights. The paucity of high resolution climate histories from the northeastern side of the Pacific Basin is a major obstacle to advancing our understanding of the rapid and recent changes in the dynamic state of the Pacific region and its global connections. Of particular interest are: 1) the warming of the last 30 years that appears to be amplified at high elevations in the tropics and subtropics and in northwestern North America and northern Asia; 2) the most recent 'step' change in the dynamics of the Pacific Basin climate regime in 1976-77; and 3) the nature of recently identified multi-decadal ENSO-like mid-latitude climate variability that may have its roots in the tropical Pacific.The field program will include geophysical and surface studies designed to select the best site on the col for recovery of two high resolution, well-preserved ice core records to about 500 meters. The results from laboratory measurements of soluble and insoluble aerosol concentrations will reveal drought and wet periods and relative storm intensities. Oxygen isotope analyses should provide a proxy for the temperature history and past atmospheric circulation patterns in this area. The high annual accumulation and cold mean annual temperatures are good indicators for thick and well preserved annual signals in the physical and chemical records that will allow excellent time control with annual resolution for the last 1000 years. The complete record should extend back at least 5,000 years. The significance of recent climatic and environmental variations must be evaluated from a perspective provided by a globally dispersed, long-term proxy climate records. Linking these records from pole to pole allows assessment of the global nature of these climatic variations and identification of critical linkages between the higher latitudes and the tropics where changes in the global heat source can trigger global-scale changes in the climate system.