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Projections of Atmospheric Nutrient Deposition to the Chesapeake Bay Watershed
Citation:
Campbell, P., J. Bash, Chris Nolte, T. Spero, E. Cooter, K. Hinson, AND L. Linker. Projections of Atmospheric Nutrient Deposition to the Chesapeake Bay Watershed. 16th Annual CMAS Conference, Chapel Hill, NC, October 23 - 25, 2017.
Impact/Purpose:
As sources of atmospheric reactive nitrogen from the burning of fossil fuel (oxidized nitrogen) decline, the emissions, transport, and fate of atmospheric reactive nitrogen from agriculture (reduced nitrogen) are altered and will likely become the dominant form of atmospheric nitrogen loading to the Chesapeake Bay.
Description:
Atmospheric deposition remains one of the largest loadings of nutrients to the Chesapeake Bay watershed. The interplay between future land use, climate, and emission changes, however, will cause shifts in the future nutrient deposition regime (e.g., oxidized vs. reduced nitrogen). Recent research indicates that the form of nitrogen deposition can have varying effects on ecosystem health, and that the impacts can be habitat or species specific. Furthermore, land use and climate changes are expected to alter key processes in the Chesapeake Bay watershed, and can potentially intensify the impact of excess nutrients. In this work, we modify the Noah land surface model in the Weather Research and Forecast (WRF) model to improve the physical connectivity of WRF/Noah when coupled to the Community Multiscale Air Quality (CMAQ) model. We use the modified WRF-CMAQ to explore the relative impacts of emission, land use, and climate changes on atmospheric nutrient deposition to the Chesapeake Bay watershed for a historical (1995 – 2004) and a future period (2045 – 2054). Regional WRF-CMAQ simulations are based on the dynamic downscaling of global Community Earth System Model (CESM) simulations that are used as initial and boundary conditions for CMAQ, and simulate agricultural practices in the agro-economic Environmental Policy Integrated Climate (EPIC) model used in the NH3 bidirectional exchange module in CMAQ. Initial model simulations show that the modified WRF -CMAQ model system can reproduce the observed deposition and ambient concentrations well, and suggest that reductions in future emissions are the largest factor contributing to a total reduction in atmospheric nitrogen deposition; however, the impacts of land use changes on nutrient deposition have not yet been fully evaluated. As sources of atmospheric reactive nitrogen from the burning of fossil fuel (oxidized nitrogen) decline, the emissions, transport, and fate of atmospheric reactive nitrogen from agriculture (reduced nitrogen) are altered and will likely become the dominant form of atmospheric nitrogen loading to the Chesapeake Bay. Results from this work aid in developing effective policies to protect ecosystems from excess nitrogen deposition in the face of climate change.
