Drought in western North America impacts the environment and economy by limiting water for municipalities, agriculture, forestry, hydropower, fisheries and recreational uses. The problem of limited water resources will be compounded by rapid population growth in the western U.S. and the loss of alpine snowpack and glaciers. This problem will be especially difficult in the southern reaches of this region, where alpine snowpack currently buffers stream flow during the summer dry season. Documenting the timing, magnitude, duration and geographic pattern of past wet and dry cycles is an important step toward understanding the causes of droughts. This research will help scientists understand the frequency, duration and magnitude of wet and dry cycles, help place the current drought impacting the region in perspective, and aid policy makers so that they can make better-informed plans regarding water resources. This EAGER grant will use Holocene lake sediment records from British Columbia to reconstruct the spatial and temporal patterns of drought and pluvial cycles along the cordillera of western North America and help identify the underlying causes of these events. The goal is to reconstruct two quantitative Holocene paleoprecipitation records using consistent multiproxy methods, and to compare the results to ongoing work on similar lakes in the western cordillera of North America. The proposed locations in central and northern British Columbia contain numerous lakes with geological and limnological characteristics similar to lakes previously studied in Washington, Oregon, Montana, and the Yukon Territory. The scientists will develop well-dated stable isotope data series from lakes that produce and preserve authigenic calcium carbonate. This carbonate records the oxygen isotope signal of lake water over time, which reflects the frequency and duration of droughts. This data will then be used in climate models to: (i) quantitatively interpret existing proxy data, (ii) identify and rank the factors that influence the frequency and intensity of aridity patterns such as synoptic teleconnections involving both El Niño Southern Oscillation-tropical Pacific climate dynamics and the Atlantic Meridional Overturning Circulation, and most importantly, (iii) reduce the uncertainty in probabilistic forecasts of future drought pattern responses to anthropogenic forcing.
Drought in western North America has serious economic consequences including impacts on groundwater, agriculture, hydropower, fisheries and energy production. Therefore, improving our understanding of the timing, magnitude, duration and geographic pattern of past wet/dry cycles are an important first step toward determining the causes of drought and their future expression. In this project we expanded on previous lake level, stable isotope and modeling studies of lacustrine systems by developing new records and combining the results with previous work on similar lake systems thereby producing a network of hydroclimate reconstructions in the western cordillera of North America. Maintaining consistency between study lakes in terms of size, hydrologic characteristics, sediment composition, etc., was a major priority of this research, because it enabled us to use the same methodologies across a wide geographical area. The focus of the work was to develop well-dated stable isotope records from lakes that produce and preserve authigenic calcium carbonate, which archives the oxygen isotope signal of lake water, which is related to drought. This data was used for modeling studies to quantitatively interpret existing proxy data, identify and rank the many factors that influence the frequency and intensity of aridity patterns such as synoptic teleconnections involving both ENSO/tropical Pacific climate dynamics and the AMOC, and reduce uncertainty in projections of future drought pattern. We complete two quantitative paleoprecipitation records spanning the Holocene from Paradise Lake and Rock Lake using consistent methods and to compare the results to ongoing work on similar lakes in the western cordillera of North America. The locations in central British Columbia and northern Montana contained numerous lakes with geological and limnological characteristics similar to those of lakes previously studied in Washington making them ideal for comparison with previous work. We were able to document century scale patterns of drought across a wide swath of western North America from British Columbia through the Pacific Northwest. We synthesized the findings from ten lake systems to see how different regions responded. We combined results from our work with studies of tree rings, speleothems, and wetland deposits to document the spatial pattern of drought in western North America.
