Datasets of stable isotope compositions in precipitation have been compiled and processed over the past decades to develop large-scale regional and global isoscapes. These isoscapes typically aggregate local observations into spatial maps of yearly or monthly amount-weighted averages masking much of the useful information. For instance catchment hydrology utilizes the seasonal variation of isotope records in temperate climates to elucidate subsurface water processes and timescales. This research is intended to determine the feasibility of applying Global and Regional Atmospheric General Circulation Models to determine the hydrologic forcing and isotope composition of precipitation at the watershed scale. Specifically four-years of observations at the Susquehanna-Shale Hills Critical Zone Observatory (CZO) will be used to determine the accuracy and precision of simulated isotope composition of precipitation. Further a 30-year record of isotopes in precipitation will be constructed to allow for a detailed investigation of long-term trends in isotope composition evolution. Results have shown the simulation accurately predicts seasonal timing of isotope compositions over the four-year record yet slightly under predicts the amplitude of the seasonal variation. A longer observation record is required to accurately determine long term trends in simulated isotope composition in precipitation associated with global processes such as climate change and El Nino.
Thomas, E., Yoshimura, K., Duffy, C. (2012): Comparison of Stable Isotope Composition in Precipitation between Atmospheric General Circulation Models and Shale Hills Critical Zone Observations. AGU Annual Fall Conference Proceedings.
This Paper/Book acknowledges NSF CZO grant support.
Image of seasonal variation of precipitation
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Seasonal variation of simulated (blue bars) and observed (red squares) isotope composition of precipitation for 2009- 2011. Outliers of simulated data have been removed.