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David Wårlind

Forskare

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Nitrogen cycling in CMIP6 land surface models : Progress and limitations

Författare

  • Taraka Davies-Barnard
  • Johannes Meyerholt
  • Sönke Zaehle
  • Pierre Friedlingstein
  • Victor Brovkin
  • Yuanchao Fan
  • Rosie A. Fisher
  • Chris D. Jones
  • Hanna Lee
  • Daniele Peano
  • Benjamin Smith
  • David Wärlind
  • Andy J. Wiltshire
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Summary, in English

The nitrogen cycle and its effect on carbon uptake in the terrestrial biosphere is a recent progression in earth system models. As with any new component of a model, it is important to understand the behaviour, strengths, and limitations of the various process representations. Here we assess and compare five land surface models with nitrogen cycles that are used as the terrestrial components of some of the earth system models in CMIP6. The land surface models were run offline with a common spin-up and forcing protocol. We use a historical control simulation and two perturbations to assess the model nitrogen-related performances: a simulation with atmospheric carbon dioxide increased by 200 ppm and one with nitrogen deposition increased by 50 kgN ha-1 yr-1. There is generally greater variability in productivity response between models to increased nitrogen than to carbon dioxide. Across the five models the response to carbon dioxide globally was 5 % to 20 % and the response to nitrogen was 2 % to 24 %. The models are not evenly distributed within the ensemble range, with two of the models having low productivity response to nitrogen and another one with low response to elevated atmospheric carbon dioxide, compared to the other models. In all five models individual grid cells tend to exhibit bimodality, with either a strong response to increased nitrogen or atmospheric carbon dioxide but rarely to both to an equal extent. However, this local effect does not scale to either the regional or global level. The global and tropical responses are generally more accurately modelled than boreal, tundra, or other high-latitude areas compared to observations. These results are due to divergent choices in the representation of key nitrogen cycle processes. They show the need for more observational studies to enhance understanding of nitrogen cycle processes, especially nitrogen-use efficiency and biological nitrogen fixation.

Avdelning/ar

  • eSSENCE: The e-Science Collaboration
  • Institutionen för naturgeografi och ekosystemvetenskap
  • MERGE: ModElling the Regional and Global Earth system
  • BECC: Biodiversity and Ecosystem services in a Changing Climate

Publiceringsår

2020

Språk

Engelska

Sidor

5129-5148

Publikation/Tidskrift/Serie

Biogeosciences

Volym

17

Issue

20

Dokumenttyp

Artikel i tidskrift

Förlag

Copernicus GmbH

Ämne

  • Physical Geography
  • Climate Research

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1726-4170