A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions
An improved representation of the carbon cycle in permafrost regions will enable more realistic projections of the future climate–carbon system. Currently JULES (the Joint UK Land Environment Simulator) – the land surface model of the UK Earth System Model (UKESM) – uses the standard four-pool RothC...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-02-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/10/959/2017/gmd-10-959-2017.pdf |
| _version_ | 1828183170734882816 |
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| author | E. J. Burke S. E. Chadburn A. Ekici |
| author_facet | E. J. Burke S. E. Chadburn A. Ekici |
| author_sort | E. J. Burke |
| collection | DOAJ |
| description | An improved representation of the carbon cycle in permafrost regions will
enable more realistic projections of the future climate–carbon system.
Currently JULES (the Joint UK Land Environment Simulator) – the land surface
model of the UK Earth System Model (UKESM) – uses the standard four-pool RothC
soil carbon model. This paper describes a new version of JULES
(vn4.3_permafrost) in which the soil vertical dimension is added to the
soil carbon model, with a set of four pools in every soil layer. The
respiration rate in each soil layer depends on the temperature and moisture
conditions in that layer. Cryoturbation/bioturbation processes, which
transfer soil carbon between layers, are represented by diffusive mixing. The
litter inputs and the soil respiration are both parametrized to decrease
with increasing depth. The model now includes a tracer so that selected soil
carbon can be labelled and tracked through a simulation. Simulations show an
improvement in the large-scale horizontal and vertical distribution of soil
carbon over the standard version of JULES (vn4.3). Like the standard version
of JULES, the vertically discretized model is still unable to simulate enough
soil carbon in the tundra regions. This is in part because JULES
underestimates the plant productivity over the tundra, but also because not
all of the processes relevant for the accumulation of permafrost carbon, such
as peat development, are included in the model. In comparison with the
standard model, the vertically discretized model shows a delay in the onset
of soil respiration in the spring, resulting in an increased net uptake of
carbon during this time. In order to provide a more suitable representation
of permafrost carbon for quantifying the permafrost carbon feedback within
UKESM, the deep soil carbon in the permafrost region (below 1 m) was
initialized using the observed soil carbon. There is now a slight drift in
the soil carbon ( < 0.018 % decade<sup>−1</sup>), but the change in
simulated soil carbon over the 20th century, when there is little climate
change, is comparable to the original vertically discretized model and
significantly larger than the drift. |
| first_indexed | 2024-04-12T06:28:29Z |
| format | Article |
| id | doaj.art-b54609ddd17d444d88966945ae9054c9 |
| institution | Directory Open Access Journal |
| issn | 1991-959X 1991-9603 |
| language | English |
| last_indexed | 2024-04-12T06:28:29Z |
| publishDate | 2017-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Geoscientific Model Development |
| spelling | doaj.art-b54609ddd17d444d88966945ae9054c92022-12-22T03:44:05ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032017-02-0110295997510.5194/gmd-10-959-2017A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regionsE. J. Burke0S. E. Chadburn1A. Ekici2Met Office Hadley Centre, Fitzroy Road, Exeter, EX1 3PB, UKUniversity of Exeter, College of Engineering, Mathematics and Physical Sciences, Exeter, EX4 4QF, UKUniversity of Exeter, College of Engineering, Mathematics and Physical Sciences, Exeter, EX4 4QF, UKAn improved representation of the carbon cycle in permafrost regions will enable more realistic projections of the future climate–carbon system. Currently JULES (the Joint UK Land Environment Simulator) – the land surface model of the UK Earth System Model (UKESM) – uses the standard four-pool RothC soil carbon model. This paper describes a new version of JULES (vn4.3_permafrost) in which the soil vertical dimension is added to the soil carbon model, with a set of four pools in every soil layer. The respiration rate in each soil layer depends on the temperature and moisture conditions in that layer. Cryoturbation/bioturbation processes, which transfer soil carbon between layers, are represented by diffusive mixing. The litter inputs and the soil respiration are both parametrized to decrease with increasing depth. The model now includes a tracer so that selected soil carbon can be labelled and tracked through a simulation. Simulations show an improvement in the large-scale horizontal and vertical distribution of soil carbon over the standard version of JULES (vn4.3). Like the standard version of JULES, the vertically discretized model is still unable to simulate enough soil carbon in the tundra regions. This is in part because JULES underestimates the plant productivity over the tundra, but also because not all of the processes relevant for the accumulation of permafrost carbon, such as peat development, are included in the model. In comparison with the standard model, the vertically discretized model shows a delay in the onset of soil respiration in the spring, resulting in an increased net uptake of carbon during this time. In order to provide a more suitable representation of permafrost carbon for quantifying the permafrost carbon feedback within UKESM, the deep soil carbon in the permafrost region (below 1 m) was initialized using the observed soil carbon. There is now a slight drift in the soil carbon ( < 0.018 % decade<sup>−1</sup>), but the change in simulated soil carbon over the 20th century, when there is little climate change, is comparable to the original vertically discretized model and significantly larger than the drift.http://www.geosci-model-dev.net/10/959/2017/gmd-10-959-2017.pdf |
| spellingShingle | E. J. Burke S. E. Chadburn A. Ekici A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions Geoscientific Model Development |
| title | A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions |
| title_full | A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions |
| title_fullStr | A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions |
| title_full_unstemmed | A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions |
| title_short | A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions |
| title_sort | vertical representation of soil carbon in the jules land surface scheme vn4 3 permafrost with a focus on permafrost regions |
| url | http://www.geosci-model-dev.net/10/959/2017/gmd-10-959-2017.pdf |
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