CLASSIC v1.0: the open-source community successor to the Canadian Land Surface Scheme (CLASS) and the Canadian Terrestrial Ecosystem Model (CTEM) – Part 1: Model framework and site-level performance

Melton, Joe R.; Arora, Vivek K.; Wisernig-Cojoc, Eduard; Seiler, Christian; Fortier, Matthew; Chan, Ed; Teckentrup, Lina

doi:10.5194/gmd-13-2825-2020

Cited by 91 publications

(92 citation statements)

References 67 publications

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“…Errors in S LAND and S OCEAN are more likely to be the main cause for the budget imbalance. For example, underestimation of the S LAND by DGVMs was reported following the eruption of Mount Pinatubo in 1991 possibly due to missing responses to changes in diffuse radiation (Mercado et al, 2009) or other yet unknown factors, and DGVMs are suspected to overestimate the land sink in response to the wet decade of the 1970s (Sitch et al, 2008). Quasi-decadal variability in the ocean sink has also been reported recently (DeVries et al, 2019(DeVries et al, , 2017Landschützer et al, 2015), with all methods agreeing on a smaller than expected ocean CO 2 sink in the 1990s and a larger than expected sink in the 2000s ( Fig.…”

Section: Budget Imbalancementioning

confidence: 99%

Global Carbon Budget 2020

Friedlingstein

O’Sullivan

Jones

et al. 2020

Earth Syst. Sci. Data

1,818

1,063

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Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2010–2019), EFOS was 9.6 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.4 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.6 ± 0.7 GtC yr−1. For the same decade, GATM was 5.1 ± 0.02 GtC yr−1 (2.4 ± 0.01 ppm yr−1), SOCEAN 2.5 ± 0.6 GtC yr−1, and SLAND 3.4 ± 0.9 GtC yr−1, with a budget imbalance BIM of −0.1 GtC yr−1 indicating a near balance between estimated sources and sinks over the last decade. For the year 2019 alone, the growth in EFOS was only about 0.1 % with fossil emissions increasing to 9.9 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.7 ± 0.5 GtC yr−1 when cement carbonation sink is included), and ELUC was 1.8 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5 ± 0.9 GtC yr−1 (42.2 ± 3.3 GtCO2). Also for 2019, GATM was 5.4 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.6 ± 0.6 GtC yr−1, and SLAND was 3.1 ± 1.2 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 409.85 ± 0.1 ppm averaged over 2019. Preliminary data for 2020, accounting for the COVID-19-induced changes in emissions, suggest a decrease in EFOS relative to 2019 of about −7 % (median estimate) based on individual estimates from four studies of −6 %, −7 %, −7 % (−3 % to −11 %), and −13 %. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2019, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. Comparison of estimates from diverse approaches and observations shows (1) no consensus in the mean and trend in land-use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent discrepancy between the different methods for the ocean sink outside the tropics, particularly in the Southern Ocean. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2020 (Friedlingstein et al., 2020).

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Section: Budget Imbalancementioning

confidence: 99%

Global Carbon Budget 2020

Friedlingstein

O’Sullivan

Jones

et al. 2020

Earth Syst. Sci. Data

1,818

1,063

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“…We realize the importance of changes in BNF, given it is the single largest natural flux of N into the coupled soil-vegetation system, yet it is highly uncertain, and we aim to address these issues in a future version of the model by exploring existing BNF formulations. Meyerholt et al (2016), for example, demonstrate the uncertainty arising from the use of five different BNF parameterizations in the context of the O-CN model. They use formulations that parameterize BNF as a function of (1) evapotranspiration; (2) NPP; (3) the leaf C : N ratio, which takes into account the energy cost for N fixation (Fisher et al, 2010); (4) plant N demand; and (5) an optimality-based approach that follows Rastetter et al (2001) in which BNF only occurs when the carbon cost of N fixation is lower than the carbon cost of root N uptake.…”

Section: Discussionmentioning

confidence: 99%

Implementation of nitrogen cycle in the CLASSIC land model

Asaadi

Arora

2021

Biogeosciences

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Abstract. A terrestrial nitrogen (N) cycle model is coupled to the carbon (C) cycle in the framework of the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC). CLASSIC currently models physical and biogeochemical processes and simulates fluxes of water, energy, and CO2 at the land–atmosphere boundary. CLASSIC is similar to most models and its gross primary productivity increases in response to increasing atmospheric CO2 concentration. In the current model version, a downregulation parameterization emulates the effect of nutrient constraints and scales down potential photosynthesis rates, using a globally constant scalar, as a function of increasing CO2. In the new model when nitrogen (N) and carbon (C) cycles are coupled, cycling of N through the coupled soil–vegetation system facilitates the simulation of leaf N amount and maximum carboxylation capacity (Vcmax) prognostically. An increase in atmospheric CO2 decreases leaf N amount and therefore Vcmax, allowing the simulation of photosynthesis downregulation as a function of N supply. All primary N cycle processes that represent the coupled soil–vegetation system are modelled explicitly. These include biological N fixation; treatment of externally specified N deposition and fertilization application; uptake of N by plants; transfer of N to litter via litterfall; mineralization; immobilization; nitrification; denitrification; ammonia volatilization; leaching; and the gaseous fluxes of NO, N2O, and N2. The interactions between terrestrial C and N cycles are evaluated by perturbing the coupled soil–vegetation system in CLASSIC with one forcing at a time over the 1850–2017 historical period. These forcings include the increase in atmospheric CO2, change in climate, increase in N deposition, and increasing crop area and fertilizer input, over the historical period. An increase in atmospheric CO2 increases the C:N ratio of vegetation; climate warming over the historical period increases N mineralization and leads to a decrease in the vegetation C:N ratio; N deposition also decreases the vegetation C:N ratio. Finally, fertilizer input increases leaching, NH3 volatilization, and gaseous losses of N2, N2O, and NO. These model responses are consistent with conceptual understanding of the coupled C and N cycles. The simulated terrestrial carbon sink over the 1959–2017 period, from the simulation with all forcings, is 2.0 Pg C yr−1 and compares reasonably well with the quasi observation-based estimate from the 2019 Global Carbon Project (2.1 Pg C yr−1). The contribution of increasing CO2, climate change, and N deposition to carbon uptake by land over the historical period (1850–2017) is calculated to be 84 %, 2 %, and 14 %, respectively.

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“…This issue was also observed at shrubland sites by Sun and Verseghy (2019), who reduced soil E by applying a site-or soil-texture-specific scaling factor to the maximum surface evaporation rate (E(0) max ). For a more broadly applicable formulation, we adopted the approach of Merlin et al (2011), which modifies the parameterization of the evaporation efficiency coefficient (β). In CLASSIC, the potential evaporation rate from bare soil, E (0) (mm s −1 ), is calculated as…”

Section: Model Modificationsmentioning

confidence: 99%

Simulating shrubs and their energy and carbon dioxide fluxes in Canada's Low Arctic with the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC)

et al. 2021

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Abstract. Climate change in the Arctic is leading to shifts in vegetation communities, permafrost degradation and alteration of tundra surface–atmosphere energy and carbon (C) fluxes, among other changes. However, year-round C and energy flux measurements at high-latitude sites remain rare. This poses a challenge for evaluating the impacts of climate change on Arctic tundra ecosystems and for developing and evaluating process-based models, which may be used to predict regional and global energy and C feedbacks to the climate system. Our study used 14 years of seasonal eddy covariance (EC) measurements of carbon dioxide (CO2), water and energy fluxes, and winter soil chamber CO2 flux measurements at a dwarf-shrub tundra site underlain by continuous permafrost in Canada’s Southern Arctic ecozone to evaluate the incorporation of shrub plant functional types (PFTs) in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC), the land surface component of the Canadian Earth System Model. In addition to new PFTs, a modification of the efficiency with which water evaporates from the ground surface was applied. This modification addressed a high ground evaporation bias that reduced model performance when soils became very dry, limited heat flow into the ground, and reduced plant productivity through water stress effects. Compared to the grass and tree PFTs previously used by CLASSIC to represent the vegetation in Arctic permafrost-affected regions, simulations with the new shrub PFTs better capture the physical and biogeochemical impact of shrubs on the magnitude and seasonality of energy and CO2 fluxes at the dwarf-shrub tundra evaluation site. The revised model, however, tends to overestimate gross primary productivity, particularly in spring, and overestimated late-winter CO2 emissions. On average, annual net ecosystem CO2 exchange was positive for all simulations, suggesting this site was a net CO2 source of 18 ± 4 g C m−2 yr−1 using shrub PFTs, 15 ± 6 g C m−2 yr−1 using grass PFTs, and 25 ± 5 g C m−2 yr−1 using tree PFTs. These results highlight the importance of using appropriate PFTs in process-based models to simulate current and future Arctic surface–atmosphere interactions.

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CLASSIC v1.0: the open-source community successor to the Canadian Land Surface Scheme (CLASS) and the Canadian Terrestrial Ecosystem Model (CTEM) – Part 1: Model framework and site-level performance

Cited by 91 publications

References 67 publications

Global Carbon Budget 2020

Global Carbon Budget 2020

Implementation of nitrogen cycle in the CLASSIC land model

Simulating shrubs and their energy and carbon dioxide fluxes in Canada's Low Arctic with the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC)

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