Projections of Atmospheric Nitrogen Deposition to the Chesapeake Bay Watershed. Issue 11 (7th November 2019)

• Record Type: Journal Article
• Authors: Campbell, Patrick C.; Bash, Jesse O.; Nolte, Christopher G.; Spero, Tanya L.; Cooter, Ellen J.; Hinson, Kyle; Linker, Lewis C.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 11(2019)
• Page Start: 3307
• Page End: 3326
• Publication Date: 2019-11-07
• Subjects: Nitrogen -- Deposition -- Climate -- WRF‐CMAQ -- Chesapeake Bay Watershed -- Emissions; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2019JG005203
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Atmospheric deposition is among the largest pathways of nitrogen loading to the Chesapeake Bay Watershed (CBW). The interplay between future climate and emission changes in and around the CBW will likely shift the future nutrient deposition abundance and chemical regime (e.g., oxidized vs. reduced nitrogen). In this work, a Representative Concentration Pathway from the Community Earth System Model is dynamically downscaled using a recently updated Weather Research and Forecasting model that subsequently drives the Community Multiscale Air Quality model coupled to the agroeconomic Environmental Policy Integrated Climate model. The relative impacts of emission and climate changes on atmospheric nutrient deposition are explored for a recent historical period and a period centered on 2050. The projected regional emissions in Community Multiscale Air Quality reflect current federal and state regulations, which use baseline and projected emission years 2011 and 2040, respectively. The historical simulations of 2‐m temperature (T2) and precipitation (PRECIP) have cool and dry biases, and temperature and PRECIP are projected to both increase. Ammonium wet deposition agrees well with observations, but nitrate wet deposition is underpredicted. Climate and deposition changes increase simulated future ammonium fertilizer application. In the CBW by 2050, these changes (along with widespread decreases in anthropogenic nitrogen oxide and sulfur oxide emissions, and relatively constant ammonia emissions) decrease total nitrogen deposition by 21%, decrease annual average oxidized nitrogen deposition by 44%, and increase reduced nitrogen deposition by 10%. These results emphasize the importance of decreased anthropogenic emissions on the control of future nitrogen loading to the Chesapeake Bay in a changing climate. Plain Language Summary: In this study a global climate scenario is used to drive a regional‐scale weather and air quality model to investigate the potential impacts of future climate and emission changes on atmospheric nitrogen loading to the Chesapeake Bay Watershed (CBW). While different scenarios are possible, here we delve into a specific climate projection that represents a future pathway for stabilization of radiative forcing by the year 2050 and use projected emissions (from human activity) that are based on historical and proposed regulations and controls from the U.S. Environmental Protection Agency. The combined climate and emission changes lead to decreases in the atmospheric nitrogen loading to the Chesapeake Bay Watershed by the year 2050, while the effects of climate alone lead to a small increase in atmospheric nitrogen loading. The results demonstrate the importance of emission reductions on nitrogen loading to the Chesapeake Bay, in the face of climate change. Key Points: Combined climate and emission changes lead to reduced nitrogen deposition (~21%) to the Chesapeake Bay Watershed by 2050 There is an offset in nitrogen deposition (approximately +4%) due to the change in climate by 2050 The composition of the nitrogen deposition is becoming increasingly dominated by reduced nitrogen by 2050