scholarly journals Improved ELMv1-ECA simulations of zero-curtain periods and cold-season CH<sub>4</sub> and CO<sub>2</sub> emissions at Alaskan Arctic tundra sites

2021 ◽  
Vol 15 (12) ◽  
pp. 5281-5307
Author(s):  
Jing Tao ◽  
Qing Zhu ◽  
William J. Riley ◽  
Rebecca B. Neumann
Keyword(s):  
Co2 Emissions ◽  
Carbon Emissions ◽  
Field Measurements ◽  
Arctic Tundra ◽  
Absolute Error ◽  
Cold Season ◽  
Earth System ◽  
Environmental Controls ◽  
Soil Temperatures ◽  
Carbon Dioxide Co2

Abstract. Field measurements have shown that cold-season methane (CH4) and carbon dioxide (CO2) emissions contribute a substantial portion to the annual net carbon emissions in permafrost regions. However, most earth system land models do not accurately reproduce cold-season CH4 and CO2 emissions, especially over the shoulder (i.e., thawing and freezing) seasons. Here we use the Energy Exascale Earth System Model (E3SM) land model version 1 (ELMv1-ECA) to tackle this challenge and fill the knowledge gap of how cold-season CH4 and CO2 emissions contribute to the annual totals at Alaska Arctic tundra sites. Specifically, we improved the ELMv1-ECA soil water phase-change scheme, environmental controls on microbial activity, and the methane module. Results demonstrate that both soil temperature and the duration of zero-curtain periods (i.e., the fall period when soil temperatures linger around 0 ∘C) simulated by the updated ELMv1-ECA were greatly improved; e.g., the mean absolute error (MAE) in zero-curtain durations at 12 cm depth was reduced by 62 % on average. Furthermore, the MAEs of simulated cold-season carbon emissions at three tundra sites were improved by 72 % and 70 % on average for CH4 and CO2, respectively. Overall, CH4 emitted during the early cold season (September and October), which often includes most of the zero-curtain period in Arctic tundra, accounted for more than 50 % of the total emissions throughout the entire cold season (September to May) in the model, compared with around 49.4 % (43 %–58 %) in observations. From 1950 to 2017, both CO2 emissions during the zero-curtain period and during the entire cold season showed increasing trends, for example, of 0.17 and 0.36 gC m−2 yr−1 at Atqasuk. This study highlights the importance of zero-curtain periods in facilitating cold-season CH4 and CO2 emissions from tundra ecosystems.

scholarly journals Improved ELMv1-ECA Simulations of Zero-Curtain Periods and Cold-season CH<sub>4</sub> and CO<sub>2</sub> Emissions at Alaskan Arctic Tundra Sites

2020 ◽  
Author(s):  
Jing Tao ◽  
Qing Zhu ◽  
William J. Riley ◽  
Rebecca B. Neumann
Keyword(s):  
Co2 Emissions ◽  
Field Measurements ◽  
Arctic Tundra ◽  
Absolute Error ◽  
Cold Season ◽  
Earth System ◽  
Environmental Controls ◽  
Soil Temperatures ◽  
Carbon Dioxide Co2 ◽  
Increasing Trends

Abstract. Field measurements have shown that cold-season methane (CH4) and carbon dioxide (CO2) emissions contribute a substantial portion to the annual net carbon emissions in permafrost regions. However, most earth system land models do not accurately reproduce cold-season CH4 and CO2 emissions, especially over the shoulder (i.e., thawing and freezing) seasons. Here we use the Energy Exascale Earth System Model (E3SM) land model version 1 (ELMv1-ECA) to tackle this challenge and fill the knowledge gap of how cold-season CH4 and CO2 emissions contribute to the annual totals at Alaska Arctic tundra sites. Specifically, we improved the ELMv1-ECA soil water phase-change scheme, environmental controls on microbial activity, and cold-season methane transport module. Results demonstrate that both soil temperature and the duration of zero-curtain periods (i.e., the fall period when soil temperatures linger around 0 °C) simulated by the updated ELMv1-ECA were greatly improved, e.g., the Mean Absolute Error in zero-curtain durations at 12 cm depth was reduced by 62 % on average. Furthermore, the simulated cold-season emissions at three tundra sites were improved by 84 % and 81 % on average for CH4 and CO2, respectively. Overall, CH4 and CO2 emitted during the early cold season (Sep. and Oct.), which often includes most of the zero-curtain period in Arctic tundra, accounted for more than 50 % of the total emissions throughout the entire cold season (Sep. to May). From 1950 to 2017, both CO2 emissions during the 12 cm depth zero-curtain period and during the entire cold season showed increasing trends, for example, of 0.26 g C m−2 year−1 and 0.38 g C m−2 year−1 at Atqasuk. This study highlights the importance of zero-curtain periods in facilitating CH4 and CO2 emissions from tundra ecosystems.

scholarly journals Environmental controls on ecosystem-scale cold-season methane and carbon dioxide fluxes in an Arctic tundra ecosystem

2020 ◽  
Vol 17 (15) ◽  
pp. 4025-4042
Author(s):  
Dean Howard ◽  
Yannick Agnan ◽  
Detlev Helmig ◽  
Yu Yang ◽  
Daniel Obrist
Keyword(s):  
Carbon Dioxide ◽  
Methane Emission ◽  
Arctic Tundra ◽  
Cold Season ◽  
The Arctic ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Carbon Dioxide Fluxes ◽  
Soil Temperatures ◽  
Annual Total

Abstract. Understanding the processes that influence and control carbon cycling in Arctic tundra ecosystems is essential for making accurate predictions about what role these ecosystems will play in potential future climate change scenarios. Particularly, air–surface fluxes of methane and carbon dioxide are of interest as recent observations suggest that the vast stores of soil carbon found in the Arctic tundra are becoming more available to release to the atmosphere in the form of these greenhouse gases. Further, harsh wintertime conditions and complex logistics have limited the number of year-round and cold-season studies and hence too our understanding of carbon cycle processes during these periods. We present here a two-year micrometeorological data set of methane and carbon dioxide fluxes, along with supporting soil pore gas profiles, that provide near-continuous data throughout the active summer and cold winter seasons. Net emission of methane and carbon dioxide in one of the study years totalled 3.7 and 89 g C m−2 a−1 respectively, with cold-season methane emission representing 54 % of the annual total. In the other year, net emission totals of methane and carbon dioxide were 4.9 and 485 g C m−2 a−1 respectively, with cold-season methane emission here representing 82 % of the annual total – a larger proportion than has been previously reported in the Arctic tundra. Regression tree analysis suggests that, due to relatively warmer air temperatures and deeper snow depths, deeper soil horizons – where most microbial methanogenic activity takes place – remained warm enough to maintain efficient methane production whilst surface soil temperatures were simultaneously cold enough to limit microbial methanotrophic activity. These results provide valuable insight into how a changing Arctic climate may impact methane emission, and highlight a need to focus on soil temperatures throughout the entire active soil profile, rather than rely on air temperature as a proxy for modelling temperature–methane flux dynamics.

scholarly journals Exploring the Role of Carbon Taxation Policies on CO2 Emissions: Contextual Evidence from Tax Implementation and Non-Implementation European Countries

2020 ◽  
Vol 12 (20) ◽  
pp. 8680 ◽  
Author(s):  
Assaad Ghazouani ◽  
Wanjun Xia ◽  
Mehdi Ben Jebli ◽  
Umer Shahzad
Keyword(s):  
Co2 Emissions ◽  
Carbon Emissions ◽  
Carbon Tax ◽  
Developing Economies ◽  
Pollutant Emissions ◽  
Carbon Taxes ◽  
Tax Reforms ◽  
Policy Tool ◽  
Carbon Dioxide Co2

During the past decades, environmental related taxes, energy, and carbon taxes has been recommended by environmental scientists as a policy tool to mitigate pollutant emissions in developed and developing economies. Among developed nations, Denmark, Finland, Sweden, the Netherlands, and Norway were the first regions to adopt a tax on carbon dioxide (CO2) emissions and research into the impacts of carbon tax on carbon emissions bring significant implications. The prime objective and goal of this work is to explore the role of carbon tax reforms for environmental quality in European economies. This is probably the first study to conduct a comparative study in European context for carbon-tax implementation and non-implementation policies. To this end, the present study reports new conclusions and implications regarding the effectiveness of environmental regulations and policies for climate change and sustainability. In the present study, the authors exhaustively explore the impacts of the carbon-tax on the mitigation of CO2 emissions. Using the propensity score matching method, the results of the estimation of the different matching methods allow us to observe a positive and significant impact of the adoption of the carbon-tax on stimulating the reduction of carbon emissions.

scholarly journals Environmental controls on ecosystem-scale cold season methane and carbon dioxide fluxes in an Arctic tundra ecosystem

2019 ◽  
Author(s):  
Dean Howard ◽  
Yannick Agnan ◽  
Detlev Helmig ◽  
Yu Yang ◽  
Daniel Obrist
Keyword(s):  
Carbon Dioxide ◽  
Methane Emission ◽  
Arctic Tundra ◽  
Cold Season ◽  
The Arctic ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Carbon Dioxide Fluxes ◽  
Soil Temperatures ◽  
Annual Total

Abstract. Understanding the processes that influence and control carbon cycling in Arctic tundra ecosystems is essential for making accurate predictions about what role these ecosystems will play in potential future climate change scenarios. Particularly, air–surface fluxes of methane and carbon dioxide are of interest as recent observations suggest that the vast stores of soil carbon found in the Arctic tundra are becoming more available to release to the atmosphere in the form of these greenhouse gases. Further, harsh wintertime conditions and complex logistics have limited the number of year-round and cold season studies and hence too our understanding of carbon cycle processes during these periods. We present here a two-year micrometeorological data set of methane and carbon dioxide fluxes that provides near-continuous data throughout the active summer and cold winter seasons. Net emission of methane and carbon dioxide in one of the study years totalled 3.7 and 89 g C m−2 a−1 respectively, with cold season methane emission representing 54% of the annual total. In the other year, net emission totals of methane and carbon dioxide were 4.9 and 485 g C m−2 a−1 respectively, with cold season methane emission here representing 82 % of the annual total – a larger proportion than has been previously reported in the Arctic tundra. Regression tree analysis suggests that, due to relatively warmer air temperatures and deeper snow depths, deeper soil horizons – where most microbial methanogenic activity takes place – remained warm enough to maintain efficient methane production whilst surface soil temperatures were simultaneously cold enough to limit microbial methanotrophic activity. These results provide valuable insight into how a changing Arctic climate may impact methane emission, and highlight a need to focus on soil temperatures throughout the entire active soil profile, rather than rely on air temperature as a proxy for modelling temperature–methane flux dynamics.

Impact of Climate Change Mitigation On Ocean Acidification Projections

2011 ◽  
Author(s):  
Fortunat Joos ◽  
Thomas L. Frölicher
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Ocean Acidification ◽  
Carbon Emissions ◽  
Climate Mitigation ◽  
Potential Range ◽  
Earth System ◽  
Emissions Scenarios ◽  
Cost Efficient ◽  
Carbon Dioxide Co2

Ocean acidification caused by the uptake of carbon dioxide (CO2) by the ocean is an important global change problem (Kleypas et al. 1999; Caldeira and Wickett 2003; Doney et al. 2009). Ongoing ocean acidification is closely linked to global warming, as acidification and warming are primarily caused by continued anthropogenic emissions of CO2 from fossil fuel burning (Marland et al. 2008 ), land use, and land-use change (Strassmann et al. 2007). Future ocean acidification will be determined by past and future emissions of CO2 and their redistribution within the earth system and the ocean. Calculation of the potential range of ocean acidification requires consideration of both a plausible range of emissions scenarios and uncertainties in earth system responses, preferably by using results from multiple scenarios and models. The goal of this chapter is to map out the spatiotemporal evolution of ocean acidification for different metrics and for a wide range of multigas climate change emissions scenarios from the integrated assessment models (Nakićenović 2000; Van Vuuren et al. 2008b). By including emissions reduction scenarios that are among the most stringent in the current literature, this chapter explores the potential benefits of climate mitigation actions in terms of how much ocean acidification can be avoided and how much is likely to remain as a result of inertia within the energy and climate systems. The longterm impacts of carbon emissions are addressed using so-called zero-emissions commitment scenarios and pathways leading to stabilization of atmospheric CO 2. Discussion will primarily rely on results from the cost-efficient Bern2.5CC model (Plattner et al. 2008) and the comprehensive carbon cycle– climate model of the National Centre for Atmospheric Research (NCAR), CSM1.4-carbon (Steinacher et al. 2009; Frölicher and Joos 2010). The magnitude of the human perturbation of the climate system is well documented by observations (Solomon e t al. 2007). Carbon emissions from human activities force the atmospheric composition, climate, and the geochemical state of the ocean towards conditions that are unique for at least the last million years (see Chapter 2).

scholarly journals Using field observations to inform thermal hydrology models of permafrost dynamics with ATS (v0.83)

2015 ◽  
Vol 8 (4) ◽  
pp. 3235-3292 ◽  
Author(s):  
A. L. Atchley ◽  
S. L. Painter ◽  
D. R. Harp ◽  
E. T. Coon ◽  
C. J. Wilson ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Thermal Response ◽  
Field Measurements ◽  
Early Summer ◽  
Active Layer Thickness ◽  
Earth System ◽  
Model Refinement ◽  
System Models ◽  
Developed Surface ◽  
Earth System Models

Abstract. Climate change is profoundly transforming the carbon-rich Arctic tundra landscape, potentially moving it from a carbon sink to a carbon source by increasing the thickness of soil that thaws on a seasonal basis. However, the modeling capability and precise parameterizations of the physical characteristics needed to estimate projected active layer thickness (ALT) are limited in Earth System Models (ESMs). In particular, discrepancies in spatial scale between field measurements and Earth System Models challenge validation and parameterization of hydrothermal models. A recently developed surface/subsurface model for permafrost thermal hydrology, the Advanced Terrestrial Simulator (ATS), is used in combination with field measurements to calibrate and identify fine scale controls of ALT in ice wedge polygon tundra in Barrow, Alaska. An iterative model refinement procedure that cycles between borehole temperature and snow cover measurements and simulations functions to evaluate and parameterize different model processes necessary to simulate freeze/thaw processes and ALT formation. After model refinement and calibration, reasonable matches between simulated and measured soil temperatures are obtained, with the largest errors occurring during early summer above ice wedges (e.g. troughs). The results suggest that properly constructed and calibrated one-dimensional thermal hydrology models have the potential to provide reasonable representation of the subsurface thermal response and can be used to infer model input parameters and process representations. The models for soil thermal conductivity and snow distribution were found to be the most sensitive process representations. However, information on lateral flow and snowpack evolution might be needed to constrain model representations of surface hydrology and snow depth.

scholarly journals Economic Development, CO2 Emissions and Energy Use Nexus-Evidence from the Danube Region Countries

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3165
Author(s):  
Eva Litavcová ◽  
Jana Chovancová
Keyword(s):  
Economic Growth ◽  
Energy Consumption ◽  
Co2 Emissions ◽  
Carbon Emissions ◽  
Bounds Testing ◽  
Mutual Cooperation ◽  
Long Run ◽  
Short Run ◽  
Danube Region ◽  
The Impact

The aim of this study is to examine the empirical cointegration, long-run and short-run dynamics and causal relationships between carbon emissions, energy consumption and economic growth in 14 Danube region countries over the period of 1990–2019. The autoregressive distributed lag (ARDL) bounds testing methodology was applied for each of the examined variables as a dependent variable. Limited by the length of the time series, we excluded two countries from the analysis and obtained valid results for the others for 26 of 36 ARDL models. The ARDL bounds reliably confirmed long-run cointegration between carbon emissions, energy consumption and economic growth in Austria, Czechia, Slovakia, and Slovenia. Economic growth and energy consumption have a significant impact on carbon emissions in the long-run in all of these four countries; in the short-run, the impact of economic growth is significant in Austria. Likewise, when examining cointegration between energy consumption, carbon emissions, and economic growth in the short-run, a significant contribution of CO2 emissions on energy consumptions for seven countries was found as a result of nine valid models. The results contribute to the information base essential for making responsible and informed decisions by policymakers and other stakeholders in individual countries. Moreover, they can serve as a platform for mutual cooperation and cohesion among countries in this region.

scholarly journals New Forest Aboveground Biomass Maps of China Integrating Multiple Datasets

2021 ◽  
Vol 13 (15) ◽  
pp. 2892
Author(s):  
Zhongbing Chang ◽  
Sanaa Hobeichi ◽  
Ying-Ping Wang ◽  
Xuli Tang ◽  
Gab Abramowitz ◽  
...  
Keyword(s):  
Carbon Emissions ◽  
Aboveground Biomass ◽  
Regional Scale ◽  
Remote Sensing Data ◽  
Field Measurements ◽  
Random Forest Regression ◽  
Multiple Datasets ◽  
Optimal Weighting ◽  
Two Hybrid ◽  
Forest Aboveground Biomass

Mapping the spatial variation of forest aboveground biomass (AGB) at the national or regional scale is important for estimating carbon emissions and removals and contributing to global stocktake and balancing the carbon budget. Recently, several gridded forest AGB products have been produced for China by integrating remote sensing data and field measurements, yet significant discrepancies remain among these products in their estimated AGB carbon, varying from 5.04 to 9.81 Pg C. To reduce this uncertainty, here, we first compiled independent, high-quality field measurements of AGB using a systematic and consistent protocol across China from 2011 to 2015. We applied two different approaches, an optimal weighting technique (WT) and a random forest regression method (RF), to develop two observationally constrained hybrid forest AGB products in China by integrating five existing AGB products. The WT method uses a linear combination of the five existing AGB products with weightings that minimize biases with respect to the field measurements, and the RF method uses decision trees to predict a hybrid AGB map by minimizing the bias and variance with respect to the field measurements. The forest AGB stock in China was 7.73 Pg C for the WT estimates and 8.13 Pg C for the RF estimates. Evaluation with the field measurements showed that the two hybrid AGB products had a lower RMSE (29.6 and 24.3 Mg/ha) and bias (−4.6 and −3.8 Mg/ha) than all five participating AGB datasets. Our study demonstrated both the WT and RF methods can be used to harmonize existing AGB maps with field measurements to improve the spatial variability and reduce the uncertainty of carbon stocks. The new spatial AGB maps of China can be used to improve estimates of carbon emissions and removals at the national and subnational scales.

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