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Earth System Dynamics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/esd-2018-19
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
22 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth System Dynamics (ESD).
Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system
Efrén López-Blanco1,2, Jean-François Exbrayat2,3, Magnus Lund1, Torben R. Christensen1,4, Mikkel P. Tamstorf1, Darren Slevin2, Gustaf Hugelius5, Anthony A. Bloom6, and Mathew Williams2,3 1Department of Biosciences, Arctic Research Center, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
2School of GeoSciences, University of Edinburgh, Edinburgh, EH93FF, UK
3National Centre for Earth Observation, University of Edinburgh, Edinburgh, EH9 3FF, UK
4Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
5Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Abstract. There is a significant knowledge gap in the current state of the terrestrial carbon (C) budget. The Arctic accounts for approximately 50 % of the global soil organic C stock, emphasizing the important role of Arctic regions in the global C cycle. Recent studies have pointed to the poor understanding of C pools turnover, although remain unclear as to whether productivity or biomass dominate the biases. Here, we use an improved version of the CARDAMOM data-assimilation system, to produce pan-Arctic terrestrial C-related variables without using traditional plant functional type or steady-state assumptions. Our approach integrates a range of data (soil organic C, leaf area index, biomass, and climate) to determine the most likely state of the high latitude C cycle at a 1° × 1° resolution for the first 15 years of the 21st century, but also to provide general guidance about the controlling biases in the turnover dynamics. As average, CARDAMOM estimates 513 (456, 579), 245 (208, 290) and 204 (109, 427) g C m−2 yr−1 (90 % confidence interval) from photosynthesis, autotrophic and heterotrophic respiration respectively, suggesting that the pan-Arctic region acted as a likely sink −55 (−152, 157) g C m−2 yr−1, weaker in tundra and stronger in taiga, but our confidence intervals remain large (and so the region could be a source of C). In general, we find a good agreement between CARDAMOM and different sources of assimilated and independent data at both pan-Arctic and local scale. Using CARDAMOM as a benchmarking tool for global vegetation models (GVM), we also conclude that turnover time of vegetation C is weakly simulated in vegetation models and is a major component of error in their forecasts. Our findings highlight that GVM modellers need to focus on the vegetation C stocks dynamics, but also their respiratory losses, to improve our process-based understanding of internal C cycle dynamics in the Arctic.
Citation: López-Blanco, E., Exbrayat, J.-F., Lund, M., Christensen, T. R., Tamstorf, M. P., Slevin, D., Hugelius, G., Bloom, A. A., and Williams, M.: Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-19, in review, 2018.
Efrén López-Blanco et al.
Efrén López-Blanco et al.

Data sets

CARDAMOM panarctic retrievals 2000-2015 J.-F. Exbrayat and M. Williams https://doi.org/10.7488/ds/2334
Efrén López-Blanco et al.

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Short summary
The terrestrial CO2 exchange in Arctic ecosystems plays an important role in the global carbon cycle and is particularly sensitive to the ongoing warming experienced in recent years. To improve our understanding of the atmosphere–biosphere interplay, we evaluated the state of the terrestrial pan-Arctic carbon cycling using a promising data assimilation system in the first 15 years of the 21st century. This is crucial when it comes to making predictions about the future state of the carbon cycle.
The terrestrial CO2 exchange in Arctic ecosystems plays an important role in the global carbon...
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