The Effect of Terrestrial Photosynthesis Down Regulation on the Twentieth-Century Carbon Budget Simulated with the CCCma Earth System Model

2009 ◽  
Vol 22 (22) ◽  
pp. 6066-6088 ◽  
Author(s):  
V. K. Arora ◽  
G. J. Boer ◽  
J. R. Christian ◽  
C. L. Curry ◽  
K. L. Denman ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Carbon Budget ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Carbon Uptake ◽  
Climate Modelling ◽  
Earth System ◽  
Down Regulation ◽  
The Tropics

Abstract The simulation of atmospheric–land–ocean CO2 exchange for the 1850–2000 period offers the possibility of testing and calibrating the carbon budget in earth system models by comparing the simulated changes in atmospheric CO2 concentration and in land and ocean uptake with observation-based information. In particular, some of the uncertainties associated with the treatment of land use change (LUC) and the role of down regulation in affecting the strength of CO2 fertilization for terrestrial photosynthesis are assessed using the Canadian Centre for Climate Modelling and Analysis Earth System Model (CanESM1). LUC emissions may be specified as an external source of CO2 or calculated interactively based on estimated changes in crop area. The evidence for photosynthetic down regulation is reviewed and an empirically based representation is implemented and tested in the model. Four fully coupled simulations are performed: with and without terrestrial photosynthesis down regulation and with interactively determined or specified LUC emissions. Simulations without terrestrial photosynthesis down regulation yield 15–20 ppm lower atmospheric CO2 by the end of the twentieth century, compared to observations, regardless of the LUC approach used because of higher carbon uptake by land. Implementation of down regulation brings simulated values of atmospheric CO2 and land and ocean carbon uptake closer to observation-based values. The use of specified LUC emissions yields a large source in the tropics during the 1981–2000 period, which is inconsistent with studies suggesting the tropics to be near-neutral or small carbon sinks. The annual cycle of simulated global averaged CO2, dominated by the Northern Hemisphere terrestrial photosynthesis and respiration cycles, is reasonably well reproduced, as is the latitudinal distribution of CO2 and the dependence of interhemispheric CO2 gradient on fossil fuel emissions. The empirical approach used here offers a reasonable method of implementing down regulation in coupled carbon–climate models in the absence of a more explicit biogeochemical representation.

scholarly journals Preindustrial-Control and Twentieth-Century Carbon Cycle Experiments with the Earth System Model CESM1(BGC)

2014 ◽  
Vol 27 (24) ◽  
pp. 8981-9005 ◽  
Author(s):  
Keith Lindsay ◽  
Gordon B. Bonan ◽  
Scott C. Doney ◽  
Forrest M. Hoffman ◽  
David M. Lawrence ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Carbon Cycle ◽  
Time Scales ◽  
Seasonal Cycle ◽  
Earth System Model ◽  
Surface Fluxes ◽  
Atmospheric Co2 ◽  
System Model ◽  
Biogeochemical Model ◽  
Earth System

Abstract Version 1 of the Community Earth System Model, in the configuration where its full carbon cycle is enabled, is introduced and documented. In this configuration, the terrestrial biogeochemical model, which includes carbon–nitrogen dynamics and is present in earlier model versions, is coupled to an ocean biogeochemical model and atmospheric CO2 tracers. The authors provide a description of the model, detail how preindustrial-control and twentieth-century experiments were initialized and forced, and examine the behavior of the carbon cycle in those experiments. They examine how sea- and land-to-air CO2 fluxes contribute to the increase of atmospheric CO2 in the twentieth century, analyze how atmospheric CO2 and its surface fluxes vary on interannual time scales, including how they respond to ENSO, and describe the seasonal cycle of atmospheric CO2 and its surface fluxes. While the model broadly reproduces observed aspects of the carbon cycle, there are several notable biases, including having too large of an increase in atmospheric CO2 over the twentieth century and too small of a seasonal cycle of atmospheric CO2 in the Northern Hemisphere. The biases are related to a weak response of the carbon cycle to climatic variations on interannual and seasonal time scales and to twentieth-century anthropogenic forcings, including rising CO2, land-use change, and atmospheric deposition of nitrogen.

scholarly journals Emergence of multiple ocean ecosystem drivers in a large ensemble suite with an Earth system model

2015 ◽  
Vol 12 (11) ◽  
pp. 3301-3320 ◽  
Author(s):  
K. B. Rodgers ◽  
J. Lin ◽  
T. L. Frölicher
Keyword(s):  
Southern Ocean ◽  
Marine Ecosystem ◽  
Marine Ecosystems ◽  
Earth System Model ◽  
System Model ◽  
Global Ocean ◽  
Earth System ◽  
Biological Productivity ◽  
The Tropics ◽  
Ecosystem Drivers

Abstract. Marine ecosystems are increasingly stressed by human-induced changes. Marine ecosystem drivers that contribute to stressing ecosystems – including warming, acidification, deoxygenation and perturbations to biological productivity – can co-occur in space and time, but detecting their trends is complicated by the presence of noise associated with natural variability in the climate system. Here we use large initial-condition ensemble simulations with an Earth system model under a historical/RCP8.5 (representative concentration pathway 8.5) scenario over 1950–2100 to consider emergence characteristics for the four individual and combined drivers. Using a 1-standard-deviation (67% confidence) threshold of signal to noise to define emergence with a 30-year trend window, we show that ocean acidification emerges much earlier than other drivers, namely during the 20th century over most of the global ocean. For biological productivity, the anthropogenic signal does not emerge from the noise over most of the global ocean before the end of the 21st century. The early emergence pattern for sea surface temperature in low latitudes is reversed from that of subsurface oxygen inventories, where emergence occurs earlier in the Southern Ocean. For the combined multiple-driver field, 41% of the global ocean exhibits emergence for the 2005–2014 period, and 63% for the 2075–2084 period. The combined multiple-driver field reveals emergence patterns by the end of this century that are relatively high over much of the Southern Ocean, North Pacific, and Atlantic, but relatively low over the tropics and the South Pacific. For the case of two drivers, the tropics including habitats of coral reefs emerges earliest, with this driven by the joint effects of acidification and warming. It is precisely in the regions with pronounced emergence characteristics where marine ecosystems may be expected to be pushed outside of their comfort zone determined by the degree of natural background variability to which they are adapted. The results underscore the importance of sustained multi-decadal observing systems for monitoring multiple ecosystems drivers.

Emergent constraints on the Southern Ocean anthropogenic carbon and heat uptake

2021 ◽  
Author(s):  
Thomas Frölicher ◽  
Jens Terhaar ◽  
Fortunat Joos
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Earth System Model ◽  
System Model ◽  
Carbon Uptake ◽  
Earth System ◽  
Excess Heat ◽  
The Past ◽  
Heat Uptake ◽  
Anthropogenic Carbon

<p>The Southern Ocean south of 30°S, occupying about a third of global surface ocean area, accounts for approximately 40% of the past anthropogenic carbon uptake and about 75% of excess heat uptake by the ocean. However, Earth system models have large difficulties in reproducing the Southern Ocean circulation, and therefore its historical and future anthropogenic carbon and excess heat uptake. In the first part of the talk, we show that there exists a tight relation across two Earth system model ensembles (CMIP5 and CMIP6) between present-day sea surface salinity in the subtropical-polar frontal zone, the formation region of mode and intermediate waters, and the past and future anthropogenic carbon uptake in the Southern Ocean. By using observations and Earth system model results, we constrain the projected cumulative Southern Ocean anthropogenic carbon uptake over 1850-2100 by the CMIP6 model ensemble to 158 ± 6 Pg C under the low-emissions scenario SSP1-2.6 and to 279 ± 14 Pg C under the high emissions scenario SSP5-8.5. Our results suggest that the Southern Ocean anthropogenic carbon sink is 14-18% larger and 46-54% less uncertain than estimated by the unconstrained CMIP6 Earth system model results. The identified constraint demonstrated the importance of the freshwater cycle for the Southern Ocean circulation and carbon cycle. In the second part of the talk, potential emergent constraints for the Southern Ocean excess heat uptake will be discussed.</p>

scholarly journals Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling

2007 ◽  
Vol 4 (1) ◽  
pp. 87-104 ◽  
Author(s):  
A. Ridgwell ◽  
J. C. Hargreaves ◽  
N. R. Edwards ◽  
J. D. Annan ◽  
T. M. Lenton ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Biogeochemical Cycling ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Geochemical Data ◽  
Model Parameters ◽  
Earth System ◽  
Export Production ◽  
Ocean Carbon

Abstract. We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model" (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the long-term (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which in its first incarnation is based around a simple single nutrient (phosphate) control on biological productivity. The addition of calcium carbonate preservation in deep-sea sediments and its role in regulating atmospheric CO2 is presented elsewhere (Ridgwell and Hargreaves, 2007). We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr−1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3) production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr-1) is close to recent marine carbonate budget estimates. The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global biogeochemical cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active biogeochemical tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global biogeochemical cycling over all but the very longest (>1 000 000 year) time-scales.

scholarly journals Implementation of the Community Earth System Model (CESM) version 1.2.1 as a new base model into version 2.50 of the MESSy framework

2016 ◽  
Vol 9 (1) ◽  
pp. 125-135 ◽  
Author(s):  
A. J. G. Baumgaertner ◽  
P. Jöckel ◽  
A. Kerkweg ◽  
R. Sander ◽  
H. Tost
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Model ◽  
The United States ◽  
Earth System Model ◽  
System Model ◽  
Climate Modelling ◽  
Earth System ◽  
Spectral Transform ◽  
Community Earth System Model ◽  
Component Models

Abstract. The Community Earth System Model (CESM1), maintained by the United States National Centre for Atmospheric Research (NCAR) is connected with the Modular Earth Submodel System (MESSy). For the MESSy user community, this offers many new possibilities. The option to use the Community Atmosphere Model (CAM) atmospheric dynamical cores, especially the state-of-the-art spectral element (SE) core, as an alternative to the ECHAM5 spectral transform dynamical core will provide scientific and computational advances for atmospheric chemistry and climate modelling with MESSy. The well-established finite volume core from CESM1(CAM) is also made available. This offers the possibility to compare three different atmospheric dynamical cores within MESSy. Additionally, the CESM1 land, river, sea ice, glaciers and ocean component models can be used in CESM1/MESSy simulations, allowing the use of MESSy as a comprehensive Earth system model (ESM). For CESM1/MESSy set-ups, the MESSy process and diagnostic submodels for atmospheric physics and chemistry are used together with one of the CESM1(CAM) dynamical cores; the generic (infrastructure) submodels support the atmospheric model component. The other CESM1 component models, as well as the coupling between them, use the original CESM1 infrastructure code and libraries; moreover, in future developments these can also be replaced by the MESSy framework. Here, we describe the structure and capabilities of CESM1/MESSy, document the code changes in CESM1 and MESSy, and introduce several simulations as example applications of the system. The Supplements provide further comparisons with the ECHAM5/MESSy atmospheric chemistry (EMAC) model and document the technical aspects of the connection in detail.

scholarly journals “Infrastructural geopolitics” of climate knowledge: the Brazilian Earth System Model and the North-South knowledge divide

Sociologias ◽  
2019 ◽  
Vol 21 (51) ◽  
pp. 44-75 ◽  
Author(s):  
Jean Carlos Hochsprung Miguel ◽  
Martin Mahony ◽  
Marko Synésio Alves Monteiro
Keyword(s):  
Climate Change ◽  
Latin American ◽  
Climate Models ◽  
Global Climate ◽  
Developed Countries ◽  
Earth System Model ◽  
System Model ◽  
Climate Modelling ◽  
Earth System ◽  
Climate Knowledge

Abstract This article examines how geopolitics are embedded into the efforts of Southern nations that try to build new climate knowledge infrastructures. It achieves this through an analysis of the composition of the international climate modelling basis of the Intergovernmental Panel on Climate Change (IPCC), viewed from the perspective of the Brazilian Earth System Model (BESM) - the scientific project which placed a Latin American country for the first time inside the global modelling bases of the IPCC. The paper argues that beyond the idea of “infrastructural globalism”, a historical process of global scientific cooperation led by developed countries, we also need to understand the “infrastructural geopolitics” of climate models. This concept seeks to describe the actions of developing countries towards minimizing the imbalance of global climate scientific production, and how these countries participate in global climate governance and politics. The analysis of the construction of BESM suggests that national investments in global climate modelling were aimed at attaining scientific sovereignty, which is closely related to a notion of political sovereignty of the nation-state within the international regime of climate change.

scholarly journals A model-based constraint of CO<sub>2</sub> fertilisation

2012 ◽  
Vol 9 (7) ◽  
pp. 9425-9451 ◽  
Author(s):  
P. B. Holden ◽  
N. R. Edwards ◽  
D. Gerten ◽  
S. Schaphoff
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Co2 Concentration ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Model Parameters ◽  
Earth System ◽  
Atmospheric Co2 Concentration ◽  
Post Industrial

Abstract. We derive a constraint on the strength of CO2 fertilisation of the terrestrial biosphere through a "top-down" approach, calibrating Earth System Model parameters constrained only by the post-industrial increase of atmospheric CO2 concentration. We derive a probabilistic prediction for the globally averaged strength of CO2 fertilisation in nature, implicitly net of other limiting factors such as nutrient availability. The approach yields an estimate that is independent of CO2 enrichment experiments and so provides a new constraint that can in principal be combined with data-driven priors. To achieve this, an essential requirement was the incorporation of a Land Use Change (LUC) scheme into the GENIE earth system model, which we describe in full. Using output from a 671-member ensemble of transient GENIE simulations we build an emulator of the change in atmospheric CO2 concentration change over the preindustrial period (1850 to 2000). We use this emulator to sample the 28-dimensional input parameter space. A Bayesian calibration of the emulator output suggests that the increase in Gross Primary Productivity in response of a doubling of CO2 from preindustrial values is likely to lie in the range 11 to 53%, with a most likely value of 28%. The present-day land-atmosphere flux (1990–2000) is estimated at −0.6 GTC yr−1 (likely in the range 0.9 to −2.0 GTC yr−1). The present-day land-ocean flux (1990–2000) is estimated at −2.2 GTC yr−1 (likely in the range −1.6 to −2.8 GTC yr−1). We estimate cumulative net land emissions over the post-industrial period (land use change emissions net of the CO2 fertilisation sink) to be 37 GTC, likely to lie in the range 130 to −20 GTC.

scholarly journals The mechanisms of North Atlantic CO<sub>2</sub> uptake in a large Earth System Model ensemble

2014 ◽  
Vol 11 (10) ◽  
pp. 14551-14585 ◽  
Author(s):  
P. R. Halloran ◽  
B. B. B. Booth ◽  
C. D. Jones ◽  
F. H. Lambert ◽  
D. J. McNeall ◽  
...  
Keyword(s):  
North Atlantic ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Sink Strength ◽  
Co2 Uptake ◽  
Earth System ◽  
Co2 Sink ◽  
Atmospheric Co2 Concentrations

Abstract. The oceans currently take up around a quarter of the carbon dioxide (CO2) emitted by human activity. While stored in the ocean, this CO2 is not influencing Earth's radiation budget; the ocean CO2 sink therefore plays an important role in mitigating global warming. CO2 uptake by the oceans is heterogeneous, with the subpolar North Atlantic being the strongest CO2 sink region. Observations over the last two decades have indicated that CO2 uptake by the subpolar North Atlantic sink can vary rapidly. Given the importance of this sink and its apparent variability, it is critical that we understand the mechanisms behind its operation. Here we explore subpolar North Atlantic CO2 uptake across a large ensemble of Earth System Model simulations, and find that models show a peak in sink strength around the middle of the century after which CO2 uptake begins to decline. We identify different drivers of change on interannual and multidecadal timescales. Short-term variability appears to be driven by fluctuations in regional seawater temperature and alkalinity, whereas the longer-term evolution throughout the coming century is largely occurring through a counterintuitive response to rising atmospheric CO2 concentrations. At high atmospheric CO2 concentrations the contrasting Ravelle factors between the subtropical and subpolar gyres, combined with the transport of surface waters from the subtropical to subpolar gyre, means that the subpolar CO2 uptake capacity is largely satisfied from its southern boundary rather than through air–sea CO2 flux. Our findings indicate that: (i) we can explain the mechanisms of subpolar North Atlantic CO2 uptake variability across a broad range of Earth System Models, (ii) a focus on understanding the mechanisms behind contemporary variability may not directly tell us about how the sink will change in the future, (iii) to identify long-term change in the North Atlantic CO2 sink we should focus observational resources on monitoring subtropical as well as the subpolar seawater CO2, (iv) recent observations of a weakening subpolar North Atlantic CO2 sink suggests that the sink strength is already in long-term decline.

scholarly journals Combined biogeophysical and biogeochemical effects of large-scale forest cover changes in the MPI earth system model

2010 ◽  
Vol 7 (1) ◽  
pp. 387-428 ◽  
Author(s):  
S. Bathiany ◽  
M. Claussen ◽  
V. Brovkin ◽  
T. Raddatz ◽  
V. Gayler
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Forest Canopy ◽  
Forest Cover ◽  
Co2 Concentration ◽  
Earth System Model ◽  
System Model ◽  
Climate Mitigation ◽  
Earth System ◽  
The Tropics

Abstract. Afforestation and reforestation have become popular instruments of climate mitigation policy, as forests are known to store large quantities of carbon. However, they also modify the fluxes of energy, water and momentum at the land surface. Previous studies have shown that these biogeophysical effects can counteract the carbon drawdown and, in boreal latitudes, even overcompensate it due to large albedo differences between forest canopy and snow. This study investigates the role forest cover plays for global climate by conducting deforestation and afforestation experiments with the earth system model of the Max Planck Institute for Meteorology (MPI-ESM). Complete deforestation of the tropics (18.75° S–15° N) exerts a global warming of 0.4 °C due to an increase in CO2 concentration by initially 60 ppm and a decrease in evapotranspiration in the deforested areas. In the northern latitudes (45° N–90° N), complete deforestation exerts a global cooling of 0.25 °C after 100 years, while afforestation leads to an equally large warming, despite the counteracting changes in CO2 concentration. Earlier model studies are qualitatively confirmed by these findings. As the response of temperature as well as terrestrial carbon pools is not of equal sign at every land cell, considering forests as cooling in the tropics and warming in high latitudes seems to be true only for the spatial mean, but not on a local scale.

scholarly journals Marine biogeochemical cycling and oceanic CO<sub>2</sub> uptake simulated by the NUIST Earth System Model version 3

2019 ◽  
Author(s):  
Yifei Dai ◽  
Long Cao ◽  
Bin Wang
Keyword(s):  
Primary Production ◽  
Large Scale ◽  
Net Primary Production ◽  
Earth System Model ◽  
System Model ◽  
Upper Ocean ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Earth System ◽  
Cmip5 Model

Abstract. In this study, we evaluate the performance of Nanjing University of Information Science and Technology Earth System Model, version 3 (hereafter NESM v3) in simulating the marine biogeochemical cycle and CO2 uptake. Compared with observations, NESM v3 reproduces reasonably well the large-scale patterns of upper ocean biogeochemical fields including nutrients, alkalinity, dissolved inorganic, chlorophyll, and net primary production. The model also reasonably reproduces current-day oceanic CO2 uptake, the total CO2 uptake is 149 PgC from 1850 to 2016. In the 1ptCO2 experiment, the NESM v3 produced carbon-climate (γ=-7.9 PgC/K) and carbon-concentration sensitivity parameters (β=0.8 PgC/ppm) are comparable with CMIP5 model results. The nonlinearity of carbon uptake in the NESM v3 accounts for 10.3% of the total carbon uptake, which is within the range of CMIP5 model results (3.6%~10.6%). Some regional discrepancies between model simulations and observations are identified and the possible causes are investigated. In the upper ocean, the simulated biases in biogeochemical fields are mainly associated with the shortcoming in simulated ocean circulation. Weak upwelling in the Indian Ocean suppresses the nutrient entrainment to the upper ocean, therefore reducing the biological activities and resulting in underestimation of net primary production and chlorophyll concentration. In the Pacific and the Southern Ocean, high-nutrient and low-chlorophyll result from the strong iron limitation. Alkalinity shows high biases in high-latitude oceans due to the strong convective mixing. The major discrepancy in biogeochemical fields is seen in the deep Northern Pacific. The simulated high concentration of nutrients, alkalinity and dissolved inorganic carbon water is too deep due to the excessive deep ocean remineralization. Despite these model-observation discrepancies, it is expected that the NESM v3 can be employed as a useful modeling tool to investigate large scale interactions between the ocean carbon cycle and climate change.

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