Citation:

Bash, J., P. Campbell, E. Cooter, T. Spero, Chris Nolte, AND L. Linker. Modeling Historical and Projected Future Atmospheric Nitrogen Loading to the Chesapeake Bay Watershed. Chesapeake Bay Webinar, Annapolis, Maryland, October 31, 2017.

Impact/Purpose:

In this study, we explore the relative impacts of changes in emissions, land use, and climate on the atmospheric nitrogen deposition to the Chesapeake Bay watershed for a historical period and a future period representative the decade surrounding 2050.

Description:

Land use and climate change are expected to alter key processes in the Chesapeake Bay watershed and can potentially exacerbate the impact of excess nitrogen. Atmospheric sources are one of the largest loadings of nitrogen to the Chesapeake Bay watershed. In this study, we explore the relative impacts of changes in emissions, land use, and climate on the atmospheric nitrogen deposition to the Chesapeake Bay watershed for a historical period and a future period representative the decade surrounding 2050. Future model simulations are based on the dynamic downscaling of global CESM (Community Earth System Model) fields that are used as initial and boundary conditions for regional WRF (Weather Research and Forecast) model simulations. The downscaled climate is also used to simulate agricultural practices in the agro-economic model EPIC (Environmental Policy Integrated Climate), which is coupled to air quality and deposition using the CMAQ (Community Multiscale Air Quality) model. Initial model simulations suggest that reductions in emissions have the largest effect, however the impact of land use change on nitrogen deposition has not yet been fully evaluated. As sources of atmospheric reactive nitrogen from the burning of fossil fuel (oxidized nitrogen) decline, contributions to the emissions, fate and transport of atmospheric reactive nitrogen from agriculture (reduced nitrogen) to the overall nitrogen deposition budget are altered and are projected to become the dominant form of atmospheric nitrogen loading to the Chesapeake Bay. Projected changes in meteorological variables that impact dissolved oxygen events will also be explored. This modeling system is used to assess the impact that emissions, land use change, and variability in downscaled future climate and meteorology have on the magnitude and composition of atmospheric nitrogen deposition.

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