Collaborative Research: Holocene Climatic Variability in Southern Alaska -- Quantitative Estimates of Temperature and Precipitation, Warm Intervals, and Possible Cyclicity

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This award will collect new data to investigate the nature of Holocene climatic variability in southern Alaska. New data generated in the project will be integrated with similar records from a developing network of sites to reconstruct the spatial-temporal pattern of change in the North Pacific and across the Arctic. The research team will reconstruct winter precipitation (which in Southern Alaska is positively correlated with the strength of the Aleutian low) and summer temperature (which places recent and projected climatic warming in the long-term context). The team will focus on intervals of warmth such as the early Holocene thermal maximum, the Medieval anomaly, and the 20th century. Detailed climatic records of these intervals may offer the long-term context for post-industrial warming and its impacts.Recent scientific results from Southern Alaska indicate that pronounced centennial-scale cycles occur throughout the Holocene which match those reported from the North Atlantic region. Cycles imply predictability and therefore may be key to understanding whether natural variations may exacerbate or mitigate anthropogenic warming. New data from other sites in Southern Alaska are needed to determine whether these cycles are reproducible and to understand their possible origin in the climatic system.Southern Alaska was chosen for the study because its maritime climate is highly sensitive to changes in the strength and location of atmospheric-circulation centers, especially the Aleutian low, which in turn is modulated by well-recognized inter-decadal modes of variability in the North Pacific (e.g., the Pacific North America pattern) and across the Northern Hemisphere (e.g., the Artic Oscillation). In addition, paleoclimatic records from this region provide an important link between previous paleoenvironmental research in Alaska to the north and paleoceanographic research in the North Pacific to the south.In general, the researchers will couple a lake (with a record of summer precipitation) with a nearby glaciated basin that registers winter precipitation. Monitoring of local weather and limnological conditions, sampling of lake water, and analysis of modern/recent sediment will be conducted to calibrate the proxies used for paleoclimatic reconstructions. Summer temperatures will be derived using transfer functions of midge assemblages and new techniques for analyzing the isotopic composition of specific organic compounds and diatom opal. Winter precipitation will be derived using a well-established correlation between summer temperature and winter precipitation at the equilibrium line of glaciers (ELA). Fluctuations in ELA will be reconstructed by studying the geomorphology of glacier forefields and the physical properties of sediment in proglacial lakes. This award targets particularly relevant aspects of climatic change by focusing on the impacts of warmth on time scales applicable to policy and ecosystem management decisions. Undergraduate and graduate students will receive first-hand training as part of an interdisciplinary team of global-change researchers. The researchers will produce educational materials for outreach to the general public via the Paleoenvironmental Arctic Sciences (PARCS) website and by development of public programs that will be used for visitor interpretive activities by the US Fish and Wildlife Service and the US National Park Service.