JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1)
<p>Understanding future changes in the terrestrial carbon cycle is important for reliable projections of climate change and impacts on ecosystems. It is well known that nitrogen (N) could limit plants' response to increased atmospheric carbon dioxide and it is therefore important to inclu...
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Copernicus Publications
2021-04-01
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Series: | Geoscientific Model Development |
Online Access: | https://gmd.copernicus.org/articles/14/2161/2021/gmd-14-2161-2021.pdf |
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doaj-4a5d2b025e2243b7b5138eb379cba448 |
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Article |
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DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
A. J. Wiltshire A. J. Wiltshire E. J. Burke S. E. Chadburn C. D. Jones P. M. Cox T. Davies-Barnard P. Friedlingstein A. B. Harper S. Liddicoat S. Sitch S. Zaehle |
spellingShingle |
A. J. Wiltshire A. J. Wiltshire E. J. Burke S. E. Chadburn C. D. Jones P. M. Cox T. Davies-Barnard P. Friedlingstein A. B. Harper S. Liddicoat S. Sitch S. Zaehle JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) Geoscientific Model Development |
author_facet |
A. J. Wiltshire A. J. Wiltshire E. J. Burke S. E. Chadburn C. D. Jones P. M. Cox T. Davies-Barnard P. Friedlingstein A. B. Harper S. Liddicoat S. Sitch S. Zaehle |
author_sort |
A. J. Wiltshire |
title |
JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) |
title_short |
JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) |
title_full |
JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) |
title_fullStr |
JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) |
title_full_unstemmed |
JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1) |
title_sort |
jules-cn: a coupled terrestrial carbon–nitrogen scheme (jules vn5.1) |
publisher |
Copernicus Publications |
series |
Geoscientific Model Development |
issn |
1991-959X 1991-9603 |
publishDate |
2021-04-01 |
description |
<p>Understanding future changes in the terrestrial carbon cycle is important
for reliable projections of climate change and impacts on ecosystems. It is
well known that nitrogen (N) could limit plants' response to increased
atmospheric carbon dioxide and it is therefore important to include a
representation of the N cycle in Earth system models. Here we present the
implementation of the terrestrial nitrogen cycle in the Joint UK Land
Environment Simulator (JULES) – the land surface scheme of the UK Earth
System Model (UKESM). Two configurations are discussed – the first one
(JULES-CN) has a bulk soil biogeochemical model and the second one is a
development configuration that resolves the soil biogeochemistry with
depth (JULES-CN<span class="inline-formula"><sub>layer</sub></span>). In JULES the nitrogen (N) cycle is based
on the existing carbon (C) cycle and represents all the key terrestrial N
processes in a parsimonious way. Biological N fixation is dependent on net
primary productivity, and N deposition is specified as an external input.
Nitrogen leaves the vegetation and soil system via leaching and a bulk gas
loss term. Nutrient limitation reduces carbon-use efficiency (CUE – ratio
of net to gross primary productivity) and can slow soil decomposition. We
show that ecosystem level N limitation of net primary productivity
(quantified in the model by the ratio of the potential amount of C that can
be allocated to growth and spreading of the vegetation compared with the
actual amount achieved in its natural state) falls at the lower end of the
observational estimates in forests (approximately 1.0 in the model compared
with 1.01 to 1.38 in the observations). The model shows more N limitation
in the tropical savanna and tundra biomes, consistent with the available
observations. Simulated C and N pools and fluxes are comparable to the
limited available observations and model-derived estimates. The
introduction of an N cycle improves the representation of interannual
variability of global net ecosystem exchange, which was more pronounced in
the C-cycle-only versions of JULES (JULES-C) than shown in estimates from
the Global Carbon Project. It also reduces the present-day CUE from a
global mean value of 0.45 for JULES-C to 0.41 for JULES-CN and 0.40 for
JULES-CN<span class="inline-formula"><sub>layer</sub></span>, all of which fall within the observational range.
The N cycle also alters the response of the C fluxes over the 20th
century and limits the CO<span class="inline-formula"><sub>2</sub></span> fertilisation effect, such that the
simulated current-day land C sink is reduced by about 0.5 Pg C yr<span class="inline-formula"><sup>−1</sup></span>
compared to the version with no N limitation. JULES-CN<span class="inline-formula"><sub>layer</sub></span>
additionally improves the representation of soil biogeochemistry, including
turnover times in the northern high latitudes. The inclusion of a
prognostic land N scheme marks a step forward in functionality and realism
for the JULES and UKESM models.</p> |
url |
https://gmd.copernicus.org/articles/14/2161/2021/gmd-14-2161-2021.pdf |
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spelling |
doaj-4a5d2b025e2243b7b5138eb379cba4482021-04-27T06:06:12ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032021-04-01142161218610.5194/gmd-14-2161-2021JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1)A. J. Wiltshire0A. J. Wiltshire1E. J. Burke2S. E. Chadburn3C. D. Jones4P. M. Cox5T. Davies-Barnard6P. Friedlingstein7A. B. Harper8S. Liddicoat9S. Sitch10S. Zaehle11Met Office Hadley Centre, Exeter, Devon, EX1 3PB, UKCollege of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UKMet Office Hadley Centre, Exeter, Devon, EX1 3PB, UKCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UKMet Office Hadley Centre, Exeter, Devon, EX1 3PB, UKCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UKCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UKCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UKCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UKMet Office Hadley Centre, Exeter, Devon, EX1 3PB, UKCollege of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UKBiogeochemical Signals Department, Max Planck Institute for Biogeochemistry, 07745 Jena, Germany<p>Understanding future changes in the terrestrial carbon cycle is important for reliable projections of climate change and impacts on ecosystems. It is well known that nitrogen (N) could limit plants' response to increased atmospheric carbon dioxide and it is therefore important to include a representation of the N cycle in Earth system models. Here we present the implementation of the terrestrial nitrogen cycle in the Joint UK Land Environment Simulator (JULES) – the land surface scheme of the UK Earth System Model (UKESM). Two configurations are discussed – the first one (JULES-CN) has a bulk soil biogeochemical model and the second one is a development configuration that resolves the soil biogeochemistry with depth (JULES-CN<span class="inline-formula"><sub>layer</sub></span>). In JULES the nitrogen (N) cycle is based on the existing carbon (C) cycle and represents all the key terrestrial N processes in a parsimonious way. Biological N fixation is dependent on net primary productivity, and N deposition is specified as an external input. Nitrogen leaves the vegetation and soil system via leaching and a bulk gas loss term. Nutrient limitation reduces carbon-use efficiency (CUE – ratio of net to gross primary productivity) and can slow soil decomposition. We show that ecosystem level N limitation of net primary productivity (quantified in the model by the ratio of the potential amount of C that can be allocated to growth and spreading of the vegetation compared with the actual amount achieved in its natural state) falls at the lower end of the observational estimates in forests (approximately 1.0 in the model compared with 1.01 to 1.38 in the observations). The model shows more N limitation in the tropical savanna and tundra biomes, consistent with the available observations. Simulated C and N pools and fluxes are comparable to the limited available observations and model-derived estimates. The introduction of an N cycle improves the representation of interannual variability of global net ecosystem exchange, which was more pronounced in the C-cycle-only versions of JULES (JULES-C) than shown in estimates from the Global Carbon Project. It also reduces the present-day CUE from a global mean value of 0.45 for JULES-C to 0.41 for JULES-CN and 0.40 for JULES-CN<span class="inline-formula"><sub>layer</sub></span>, all of which fall within the observational range. The N cycle also alters the response of the C fluxes over the 20th century and limits the CO<span class="inline-formula"><sub>2</sub></span> fertilisation effect, such that the simulated current-day land C sink is reduced by about 0.5 Pg C yr<span class="inline-formula"><sup>−1</sup></span> compared to the version with no N limitation. JULES-CN<span class="inline-formula"><sub>layer</sub></span> additionally improves the representation of soil biogeochemistry, including turnover times in the northern high latitudes. The inclusion of a prognostic land N scheme marks a step forward in functionality and realism for the JULES and UKESM models.</p>https://gmd.copernicus.org/articles/14/2161/2021/gmd-14-2161-2021.pdf |