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Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth system model: implications for present and future nitrogen deposition fluxes over North America

Paulot, Fabien and Malyshev, Sergey and Nguyen, Tran and Crounse, John D. and Shevliakova, Elena and Horowitz, Larry W. (2018) Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth system model: implications for present and future nitrogen deposition fluxes over North America. Atmospheric Chemistry and Physics, 18 (24). pp. 17963-17978. ISSN 1680-7324. https://resolver.caltech.edu/CaltechAUTHORS:20190104-094928097

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Abstract

Reactive nitrogen (N) emissions have increased over the last 150 years as a result of greater fossil fuel combustion and food production. The resulting increase in N deposition can alter the function of ecosystems, but characterizing its ecological impacts remains challenging, in part because of uncertainties in model-based estimates of N dry deposition. Here, we use the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric chemistry–climate model (AM3) coupled with the GFDL land model (LM3) to estimate dry deposition velocities. We leverage the tiled structure of LM3 to represent the impact of physical, hydrological, and ecological heterogeneities on the surface removal of chemical tracers. We show that this framework can be used to estimate N deposition at more ecologically relevant scales (e.g., natural vegetation, water bodies) than from the coarse-resolution global model AM3. Focusing on North America, we show that the faster removal of N over forested ecosystems relative to cropland and pasture implies that coarse-resolution estimates of N deposition from global models systematically underestimate N deposition to natural vegetation by 10% to 30% in the central and eastern US. Neglecting the sub-grid scale heterogeneity of dry deposition velocities also results in an underestimate (overestimate) of the amount of reduced (oxidized) nitrogen deposited to water bodies. Overall, changes in land cover associated with human activities are found to slow down the removal of N from the atmosphere, causing a reduction in the dry oxidized, dry reduced, and total (wet+dry) N deposition over the contiguous US of 8%, 26%, and 6%, respectively. We also find that the reduction in the overall rate of removal of N associated with land-use change tends to increase N deposition on the remaining natural vegetation and facilitate N export to Canada. We show that sub-grid scale differences in the surface removal of oxidized and reduced nitrogen imply that projected near-term (2010–2050) changes in oxidized (−47%) and reduced (+40%) US N emissions will cause opposite changes in N deposition to water bodies (increase) and natural vegetation (decrease) in the eastern US, with potential implications for acidification and ecosystems.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.5194/acp-18-17963-2018DOIArticle
https://www.atmos-chem-phys.net/18/17963/2018/acp-18-17963-2018-supplement.pdfPublisherSupporting Information
ORCID:
AuthorORCID
Paulot, Fabien0000-0001-7534-4922
Malyshev, Sergey0000-0001-6259-1043
Crounse, John D.0000-0001-5443-729X
Additional Information:© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 06 Jun 2018 – Discussion started: 19 Jul 2018 – Revised: 09 Nov 2018 – Accepted: 01 Dec 2018 – Published: 18 Dec 2018. This study was supported by the NOAA Climate Program Office’s Atmospheric Chemistry, Carbon Cycle, and Climate program (grant no. NA14OAR4320106). Caltech observations and John D. Crounse were supported by the NSF (grant no. AGS-1240604). We thank Vaishali Naik, Arlene Fiore, Jordan Schnell, and three anonymous reviewers for helpful comments. Author contributions. FP designed the research, developed and implemented the dry deposition model with help from SM, and performed the simulations and analysis. TN and JDC collected the observations at SOAS and estimated the deposition velocities. FP wrote the paper with inputs from SM, TN, JDC, ES, and LWH. Data availability. Model outputs are available upon request to Fabien Paulot. Instruction to run the AM3 model are available at https://www.gfdl.noaa.gov/am3/ (last access: 14 December 2018). Supplement. The supplement related to this article is available online at: https://doi.org/10.5194/acp-18-17963-2018-supplement. The authors declare that they have no conflict of interest. Disclaimer. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of NOAA. Edited by: Ronald Cohen. Reviewed by: three anonymous referees.
Funders:
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)NA14OAR4320106
NSFAGS-1240604
Issue or Number:24
Record Number:CaltechAUTHORS:20190104-094928097
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190104-094928097
Official Citation:Paulot, F., Malyshev, S., Nguyen, T., Crounse, J. D., Shevliakova, E., and Horowitz, L. W.: Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth system model: implications for present and future nitrogen deposition fluxes over North America, Atmos. Chem. Phys., 18, 17963-17978, https://doi.org/10.5194/acp-18-17963-2018, 2018.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92089
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:05 Jan 2019 00:21
Last Modified:03 Oct 2019 20:40

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