Funding is provided to develop precisely dated, high-resolution speleothem-based records of climate change in the Sierra Nevada. The researchers are testing two hypotheses: (1) Sierra speleothems were precipitated in isotopic and geochemical equilibrium with drip waters, and thus archive short-lived changes in regional precipitation, temperature, and vegetation density; and (2) shifts in the position of the polar jet stream and associated winter storm tracks over mid-latitude western North America, forced by large-scale reorganization of the climate system, are archived in Sierra speleothem isotopic and geochemical compositions.
To test these hypotheses, the researchers will: 1) complete in situ measurements of surface, soil and cave conditions; 2) analyze the isotopic and trace element contents in modern drip and source waters and recent calcite precipitates to define the natural intra- and inter-cave variability in drip-waters and speleothem calcites and to evaluate the presence of isotopic and trace element equilibrium precipitation of speleothem calcite; and 3) develop precisely dated (U-series with better than 2% precision) geochemical and isotopic time series (minimally multi-decadal-resolution) for stalagmites from three caves.
The broader impacts involve improved understanding of the sensitivity of winter storm tracks and mean annual precipitation levels in the mid-latitudes of western North America to changes in northern high-latitude conditions with warming atmospheric temperatures. The project also helps support two graduate students involved with the research.
