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- Title
Assessing the representation of the Australian carbon cycle in global vegetation models.
- Authors
Teckentrup, Lina; Kauwe, Martin G. De; Pitman, Andrew J.; Goll, Daniel; Haverd, Vanessa; Jain, Atul K.; Joetzjer, Emilie; Kato, Etsushi; Lienert, Sebastian; Lombardozzi, Danica; McGuire, Patrick C.; Melton, Joe R.; Nabel, Julia E. M. S.; Pongratz, Julia; Sitch, Stephen; Walker, Anthony P.; Zaehle, Sönke
- Abstract
Australia plays an important role in the global terrestrial carbon cycle on inter-annual timescales. While the Australian continent is included in global assessments of the carbon cycle such as the global carbon budget, the performance of dynamic global vegetation models (DGVMs) over Australia has rarely been evaluated. We assessed simulations of net biome production (NBP) and the carbon stored in vegetation between 1901 to 2018 from 13 DGVMs (TRENDY v8 ensemble). We focused our analysis on both Australia's short-term (inter-annual) and long-term (decadal to centennial) terrestrial carbon dynamics. The TRENDY models simulated differing magnitudes of NBP on inter-annual timescales, and these differences contributed to carbon accumulation in the vegetation on decadal to centennial timescales (-4.7-9.5 PgC). We compared the TRENDY ensemble to several satellite-derived datasets and showed that the spread in the models' simulated carbon storage resulted from varying changes in carbon residence time rather than differences in net carbon uptake. Differences in simulated long-term accumulated NBP between models were mostly due to model responses to land-use change. The DGVMs also simulated different sensitivities to atmospheric carbon dioxide (CO2) concentration, although notably, the models with nutrient cycles did not simulate the smallest NBP response to CO2. Our results suggest that a change in the climate forcing did not have a large impact on the carbon cycle on long timescales. However, the inter-annual variability in precipitation drives the year-to-year variability in NBP. We analysed the impact of key modes of climate variability, including the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on NBP. While the DGVMs agreed on sign of the response of NBP to El Nino and La Nina, and to positive and negative IOD events, the magnitude of inter-annual variability in NBP differed strongly between models. In addition, we identified differences in the timing of simulated phenology and fire dynamics associated with differences in simulated/prescribed vegetation composition and process representation. Model disagreement in simulated vegetation carbon, phenology and apparent carbon residence time, indicates the models have different types of vegetation cover across Australia (whether prescribed or emergent). Our study highlights the need to evaluate parameter assumptions and the key processes that drive vegetation dynamics, such as phenology, mortality and fire, in an Australian context to reduce uncertainty across models.
- Subjects
AUSTRALIA; CARBON cycle; SOUTHERN oscillation; EL Nino; ATMOSPHERIC carbon dioxide; NUTRIENT cycles; LA Nina
- Publication
Biogeosciences Discussions, 2021, p1
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bg-2021-66