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Title: Divergent predictions of carbon storage between two global land models: Attribution of the causes through traceability analysis

Representations of the terrestrial carbon cycle in land models are becoming increasingly complex. It is crucial to develop approaches for critical assessment of the complex model properties in order to understand key factors contributing to models' performance. In this study, we applied a traceability analysis which decomposes carbon cycle models into traceable components, for two global land models (CABLE and CLM-CASA') to diagnose the causes of their differences in simulating ecosystem carbon storage capacity. Driven with similar forcing data, CLM-CASA' predicted – 31 % larger carbon storage capacity than CABLE. Since ecosystem carbon storage capacity is a product of net primary productivity (NPP) and ecosystem residence time (τE), the predicted difference in the storage capacity between the two models results from differences in either NPP or τE or both. Our analysis showed that CLM-CASA'simulated 37 % higher NPP than CABLE. On the other hand, τE, which was a function of the baseline carbon residence time (τ'E) and environmental effect on carbon residence time, was on average 11 years longer in CABLE than CLM-CASA'. This difference in τE was mainly caused by longer τ'E of woody biomass (23 vs. 14 years in CLM-CASA'), and higher proportion of NPP allocated to woody biomass (23 vs. 16 %). Differencesmore » in environmental effects on carbon residence times had smaller influences on differences in ecosystem carbon storage capacities compared to differences in NPP and τ'E. Altogether, the traceability analysis showed that the major causes of different carbon storage estimations were found to be parameters setting related to carbon input and baseline carbon residence times between two models.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [6]
  1. Univ. of Oklahoma, Norman, OK (United States); Pacific Northwest National Lab., College Park, MD (United States)
  2. Univ. of Oklahoma, Norman, OK (United States); East China Normal Univ., Shanghai (China)
  3. Univ. of Oklahoma, Norman, OK (United States); Pacific Forestry Centre, Victoria, BC (Canada)
  4. Pacific Northwest National Lab., College Park, MD (United States)
  5. CSIRO Ocean and Atmosphere Flagship, Aspendale, VIC (Australia)
  6. Univ. of Oklahoma, Norman, OK (United States)
Publication Date:
OSTI Identifier:
1256395
Report Number(s):
PNNL-SA--115823
Journal ID: ISSN 2190-4987
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Earth System Dynamics (Online)
Additional Journal Information:
Journal Name: Earth System Dynamics (Online); Journal Volume: 7; Journal Issue: 3; Journal ID: ISSN 2190-4987
Publisher:
European Geosciences Union
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES traceability framework; partitioning coefficients; transfer coefficients; carbon storage; ecosystem carbon residence time; environmental scalars