BG1.7
Orals: Tue, 25 Apr | Room N2
Africa contributes significantly to the global greenhouse gases (GHG) budget through extensive land use change that is driven by rapid population growth and low human development status. As part of the REgional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project, we developed a comprehensive GHG budget for the period 2009-2019 for Africa. We considered bottom-up process-based models, data-driven remotely sensed products, and national greenhouse gas inventories in comparison with top-down atmospheric inversions, accounting also for lateral fluxes. We incorporated emission estimates derived from novel methodologies for termites, herbivores, and fire, which are of particular importance in Africa. We further constrained global biomass change products with high-quality local observation data. During the RECCAP2 period, Africa remains a net sink for carbon. Emissions from land cover change represents the largest contribution to the African budget. However, land cover change emissions in the drier savanna regions were largely offset by increased vegetation growth in the wet tropics. Additionally, fire emissions decreased as suggested by strong reductions in burned area. Burning of fuelwood has however increased. As expected, an upward trend in anthropogenic fossil fuel emissions was evident, ascribed to an increasing demand for energy by a growing and developing population. For all the component fluxes, uncertainty and interannual variability is large, which highlights the need for increased efforts to address Africa-specific data gaps. However, for RECCAP2, we have improved our overall understanding of many of the important components of the African GHG budget that will help to inform climate policy and action.
How to cite: Ernst, Y. and Archibald, S. and the RECCAP2 Africa team: The African greenhouse gases budget: flux trends and uncertainties for the 2009-2019 period , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-606, https://doi.org/10.5194/egusphere-egu23-606, 2023.
Understanding climate change and possible solutions to recent increases in concentrations of major GHG concentrations dependent upon quantifying the emission inventory of these gases. The objective of this study, which is part of the Regional Carbon Cycle Assessment and Processes-2 (RECCAP2) project, is to estimate the country-specific GHGs budget (sources and sinks) for the South Asia (SA) region for the 2010s. The region comprises seven countries: Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka. Each country in the region is experiencing rapid changes due to the continuous development of agriculture, deforestation, reforestation, afforestation, and the increased demand for land for people to live in. In this study, we synthesize top-down (TD) and bottom-up (BU) model results and ground-based and other data sets to estimate the GHG emissions for carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) due to anthropogenic and natural biospheric activities. Major contributing factors include net biome productivity, fossil fuel emissions, inland waters, and wetland and wet/dry soils. Our study shows that the SA region was the net source of atmospheric CO2 for the 2010s. BU estimates for CO2, CH4, and N2O emissions were 1974, 1047, and 715 Tg CO2eq, and TD estimates were 2010, 1247, and 799 Tg CO2 eq. The total GHG emission for the region based on BP and TD were 3736 and 4056 Tg CO2 eq. Among SA countries, India was the most significant contributor to the total GHG emission.
How to cite: Jain, A., Anand, J., Chandra, N., and Patra, P.: Greenhouse gas budget for South Asia region, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16920, https://doi.org/10.5194/egusphere-egu23-16920, 2023.
Accurate national carbon budget assessments allow nations to evaluate their progress in cutting carbon emissions and therefore be aligned with the Paris Climate Agreement goals. To support the initiative of The REgional Carbon Cycle Assessment and Processes (RECCAP-2), we built a synthesis of the Australasia (Australia and New Zealand) terrestrial carbon budget for 2010-2019 based on top-down and bottom-up approaches. Major carbon flux components in the bottom-up budget (e.g., net primary productivity and heterotrophic respiration) were simulated by CABLE model, Biome-BGC model and Cewn simulations. In addition, this budget include carbon flux components from the land-ocean aquatic continuum, such as inland waters, estuaries, blue carbon ecosystems, and continental shelves and carbon fluxes embodied in trade (export and import) of crops, woods, livestock and fossil fuel. We reconciled Australia and New Zealand bottom-up budgets separately with fluxes derived from regional and global OCO-2, GOSAT flux inversions, as well as fluxes obtained from in-situ measurement only (CarbonWatchNZ). We found that annual mean budgets for Australia agree relatively well (within the uncertainty range) with regional and global top-down GOSAT and OCO-2 flux estimates. New Zealand's annual bottom-up carbon budget also agrees relatively well with fluxes derived from CarbonWatchNZ inversion and GOSAT but disagrees with global flux estimates from OCO-2.
How to cite: Villalobos, Y., Canadell, P., Briggs, P., Harman, I., Keller, E. D., Bukosa, B., Mikaloff-Fletcher, S. E., Smith, B., Kirschbaum, M. UF., Giltrap, D., Liang, L., Lauerwald, R., Rosentreter, J., Maavara, T., Resplandy, L., Rayner, P. J., Schöemann, E., and Basu, S.: A comprehensive synthesis of anthropogenic and natural sources and sinks of Australasia carbon budget (2010-2019), EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15006, https://doi.org/10.5194/egusphere-egu23-15006, 2023.
Land-based mitigation is essential in reducing carbon emissions. Yet, the attribution of land carbon fluxes to their sinks and sources remains highly uncertain, in particular for the forest-rich but data-poor region of Eastern Europe. Here we integrate various data sources (from top-down and bottom-up modelling, earth observation, inventories) to show that Eastern Europe accounted for an annual aboveground biomass (AGB) carbon sink of ~0.49 GtC in 2010‑2019, or about 75% of the entire European carbon uptake. However, we find that the land-based carbon sink is declining. This declining trend is mainly driven by changes in land use and land management, but also by increasing natural disturbances due to ongoing climate change. Despite the high overall importance of environmental factors such as soil moisture, nitrogen and CO2 for enhancing the land-based carbon sink, we find indicators of a saturation effect of the regrowth in abandoned former agricultural areas, combined with an increase in wood harvest, particularly in European Russia. Our results contribute to a better understanding of the regional carbon budget of Eastern Europe and its trend. This study sheds light on land use and management as drivers of the land-based carbon sink and their role for climate mitigation.
How to cite: Winkler, K., Yang, H., Ganzenmüller, R., Fuchs, R., Ceccherini, G., Duveiller, G., Grassi, G., Pongratz, J., Bastos, A., Shvidenko, A., Araza, A., Herold, M., and Ciais, P.: Impacts of land use and environmental change on the Eastern European land carbon sink, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13792, https://doi.org/10.5194/egusphere-egu23-13792, 2023.
The Amazon is the largest continuous tropical forest in the world and plays a key role in the global carbon cycle. Human-induced disturbances (e.g., deforestation and wildfires) in combination with climate change have impacted its carbon cycling. However, uncertainties remain on the magnitude of carbon fluxes associated with human-induced disturbances and the old-growth forest sink, and thus the net land carbon balance of the Amazon. Here we synthesize state-of-the-art estimates of the land carbon flux components in the Amazon. To quantify the human-disturbance fluxes from deforestation, land use and land cover changes and degradation, we use a set of bookkeeping models. The annual intact sink was quantified using a set of 16 Dynamic Global Vegetation Models (DGVMs). We then combine the carbon flux estimates from disturbances with the intact sink estimates to provide a bottom-up estimate of the net land carbon flux and compare them alongside top-down estimates from atmospheric model inversions. Between 2010 and 2018, the net land carbon flux in the Brazilian Amazon estimated with the bottom-up approach was -59 (±160) Tg C yr-1 and +36 (±125) Tg C yr-1 with the top-down approach. Despite disagreeing on the sign of the flux, this analysis suggests that the Brazilian Amazon was on average near carbon neutral over the 2010-2018 period, given the large uncertainties underlying both methods. The net land carbon fluxes for the years 2019 and 2020 based on the bottom-up approach were larger than for 2010-2018. This is likely primarily due to direct emissions related to an increase in deforestation although it may possibly be partly caused by a weakening of the forest carbon sink, both in response to deforestation and a warming climate. Spatially, both methodologies agree that the south-eastern Amazon was a net carbon source over the whole study period. These results have important implications for the mitigation potential of Brazilian ecosystems within the goals of the Paris Agreement.
How to cite: Rosan, T. M., Sitch, S., O’Sullivan, M., Wilson, C., Basso, L. S., Fawcett, D., Heinrich, V. A., Souza, J. G., von Randow, C., Mercado, L. M., Gloor, E., Gatti, L., Friedlingstein, P., Wiltshire, A., Pongratz, J., Schwingshackl, C., and Aragão, L. E. O. C. and the TRENDY-v11 Team: The contemporary Amazon Forest carbon budget , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3228, https://doi.org/10.5194/egusphere-egu23-3228, 2023.
Fires in the tropics are linked to both climate and land-use change. While in the Amazon, deforestation-related fires decreased following a substantial reduction in deforestation activities until 2012, there have been recent upturns in deforestation and forest fires. Furthermore, earth system models predict a further increase in the intensity of dry seasons in this region in the 21st century. Therefore, carbon emissions from drought-induced forest fires can counteract further pledged deforestation reductions in the following decades, yet they are only partially accounted for in national carbon emission estimates. Improved assessments of fire impacts, including the carbon fluxes arising from post-fire mortality and regrowth, are therefore highly important.
Combining a range of available satellite products enables spatially specific fire emissions estimations. We developed a remote sensing based approach where biomass maps, observed forest loss, burned area and active fire data are combined to generate updated fuel load and emission estimates. In addition, space-for-time methods are employed to derive estimates of post-fire mortality as a function of pre-fire biomass. This high-resolution model guarantees an improved separation of fire types, and we can report emissions associated with deforestation, forest degradation and savanna fires for the entire Amazon basin and the Brazilian Cerrado at monthly intervals.
Results show that over 2015-2020 fires cause annual gross emissions of ~300 Tg C over the Amazon and Cerrado. While instantaneous emissions from forest fires are small, the fire-induced mortality and subsequent decomposition cause legacy fluxes which are closer to deforestation fire emissions in magnitude, highlighting their importance. Recent upturns in deforestation fire emissions were observed, including in conservation areas established before 2004. There is overall good agreement with previous instantaneous fire emission estimates from other approaches (GFED4s, GFED 500 m) while remaining disagreements highlight areas of uncertainties, such as combustion completeness values, which could benefit from additional field measurements and spatial modelling supported by EO products.
Outputs from this work can further be used to improve regional greenhouse gas budgets and inform emission reduction and mitigation efforts.
How to cite: Fawcett, D., Ng, L., Tai, A., Yan, X., Rosan, T., Silva Junior, C., Bastos, A., Ciais, P., Albergel, C., Aragão, L., and Sitch, S.: Carbon fluxes from different fire types in the Amazon and Cerrado biomes quantified using Earth-observation based modelling, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6173, https://doi.org/10.5194/egusphere-egu23-6173, 2023.
Wildfires are an integral part of boreal forest dynamics. Understanding the carbon loss/recovery associated with fires is crucial to assess the stability of these slow-growing forests. Yet, the carbon balance from fires and post-fire forest recovery remain uncertain at the biome scale due to the lack of spatial details about rates of forest regrowth. Here, we quantify carbon losses from fire emissions and gains from post-fire regrowth using high spatial-resolution satellite data and a bookkeeping model. We combined a 35-year long record of burned area from the Landsat satellites since 1985 with local biomass-age regrowth curves derived from high-resolution satellite-based above ground biomass (AGB) datasets. We found that forests in Eurasia tend to recover faster and reach higher biomass levels than those in North America. Young forests recovering from post-1985 wildfires produced a carbon sink of 652±200 TgC during the period 1985 to 2020. The additional recovery of older secondary forests that burned before 1985 further adds a cumulative sink of 1659±346 TgC. Comparatively, old-growth forests that did not burn accumulated 930±233 TgC during the period 1985-2020. This result shows 71% of the contemporary carbon sink in AGB is contributed by recovery from fires. After accounting for fire emissions each year and for the slow decay of coarse woody debris after burning, the net AGB carbon sink in boreal forests is 2108±234 TgC during 1985-2020. This study provides the first spatially explicit aboveground observation-based carbon budget of boreal forests and provides insights on the key factors that will control its future evolution.
How to cite: Xu, Y., Ciais, P., Li, W., Saatchi, S., Santoro, M., Cescatti, A., Shchepashchenko, D., He, G., Guido, C., He, J., Fan, L., Brandt, M., Fensholt, R., Wigneron, J.-P., Kay, H., Sitch, S., Bastos, A., Bowing, S., Ritter, F., and Fayad, I.: Biomass recovery after fires dominates the carbon sink of boreal forests over the last three decades, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9695, https://doi.org/10.5194/egusphere-egu23-9695, 2023.
Methane (CH4) levels in the atmosphere increased by 15.1 ± 0.4 ppb in 2020, the highest annual increase from 1984 to 2020, despite a likely decrease in anthropogenic CH4 emissions during COVID-19 confinements. Here, we used bottom-up and top-down methods to quantify the changes in different sources of CH4, and in its atmospheric sink due to the hydroxyl radical (OH) in 2020 compared to 2019. Bottom-up methods showed that, globally, total anthropogenic emissions slightly decreased by ~1.2 Tg CH4 yr-1, fire emissions were lower than in 2019 by ~6.5 Tg CH4 yr-1, and wetland emissions increased by 6.0 ± 2.3 Tg CH4 yr-1. In addition to higher wetland emissions in 2020 than 2019 from bottom-up, we found a decrease of 1.6–1.8% in tropospheric OH concentration relative to 2019, mainly due to lower anthropogenic NOx emissions and associated lower free tropospheric ozone during the confinements. Based on atmospheric CH4 observations from the surface network, and considering the decrease in OH, using top-down inversions, we infer that global net emissions increased by 6.9 ± 2.1 Tg CH4 yr-1 in 2020 relative to 2019, while the global CH4 removal from reaction with OH in the atmosphere decreased in 2020 by 7.5 ± 0.8 Tg CH4 yr-1. Therefore, we attribute the positive growth rate anomaly of atmospheric CH4 in 2020 relative to 2019 to lower OH sink (53 ± 10%) and higher natural emissions (47 ± 16%), mostly from wetlands. Warmer and wetter climate conditions in the Northern Hemisphere promoted wetland emissions, but fires decreased in the Southern Hemisphere, compared to the previous year. Our study highlights that northern microbial emissions of CH4 are highly sensitive to a warmer and wetter climate and could act as a positive feedback in the future. Our study also hints that the global CH4 pledge must be implemented by taking into account NOx emissions trend, whose reduction lengthens the lifetime of atmospheric CH4.
How to cite: Peng, S., Lin, X., Thompson, R., Xi, Y., Liu, G., Lan, X., Hauglustaine, D., Poulter, B., Ramonet, M., Saumois, M., Yin, Y., Zhang, Z., Zheng, B., and Ciais, P.: Why atmospheric methane surged in 2020?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8372, https://doi.org/10.5194/egusphere-egu23-8372, 2023.
Increasing extreme events and drastic shifts in the variability, intensity and frequency of droughts, heavy precipitation and frost are predicted to accompany further climate change. It is most likely that an increasing occurrence of such events will be accompanied by soil feedback of GHG emissions, particularly of nitrous oxide (N2O) known to be an extremely sensitive GHG. The increase in extreme events can lead to an increased occurrence of short-term emission pulses, referred to as ‘hot moments’, which can contribute significantly to the total annual N2O emission balance.
To account for this potential feedback to the climate system, biogeochemical models driven by climate projections of multi-model ensembles (CPM) can be used to generate scenarios observing future trends in N2O emission behavior.
Most commonly, the CPM average is used as climate input in biogeochemical models. While averaging CPM’s may provide the best overall comparison with real mean climate change, it poses the risk of ‘averaging out’ expected extreme events, thereby biasing soil-atmosphere feedbacks and future N2O emission trends!
We follow the hypothesis, that for nitrogen-saturated soils as common in industrialized countries, the annual N2O emissions simulated by the averaged CPM differ from the average annual N2O emissions simulated by the individual CPM’s, as hot moment inducing extreme climate events are averaged as well.
For our biogeochemical model simulations, we used weather data from ten selected individual climate-projections based on the multi-model ensemble of the EURO-CORDEX initiative. To focus on the effects of climate and to exclude possible biases, remaining input parameters were unified, i.e., homogeneous soil horizons and a single crop rotation were assumed. In addition, each simulation period was initialised with the same parameters to exclude possible changes in fluxes resulting from soil carbon and nitrogen cycling.
First results with CANDY and LDNDC seem to support our hypothesis, showing that annual N2O emissions simulated with the averaged CPM differ clearly from those resulting from the output mean of the individual CPM’s.
This emphasises to consider using the averaged output based on individual CPM’s rather than relying solely on averaged CPM’s for predicting future N2O emission trends.
How to cite: Hey, L., F. Jungkunst, H., and H. E. Meurer, K.: A potential bias using averaged climate projection multi model ensembles when forecasting nitrous oxide emissions from soils under climate change, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8208, https://doi.org/10.5194/egusphere-egu23-8208, 2023.
Global net biome production (NBP), or net land carbon uptake, has been repeatedly shown to increase during recent decades. However, whether the temporal variability and autocorrelation of NBP has changed during this period remains elusive. Answering this question is particularly relevant given that an increase in both could indicate destabilising C sinks and potentially lead to abrupt changes. We investigated the trends and controls of net land C uptake and its temporal variability and autocorrelation, from 1981 to 2018, using two atmospheric inversion models, the amplitude of the seasonal cycle of atmospheric CO2 derived from nine monitoring stations distributed across the Pacific Ocean, and 12 dynamic global vegetation models. Spatially, we found that plant biodiversity presented a convex parabolic relationship with NBP and its temporal variability at the global scale while nitrogen deposition generally increased annual NBP. We also found that annual NBP and its interdecadal temporal variability globally increased, but temporal autocorrelation decreased. Regions characterized by increasingly variable NBP were usually with warmer and with increasingly variable temperatures, and lower and weaker trends in NBP compared to those where NBP variability did not increase, where NBP became stronger. Annual temperature increase and its increasing temporal variability were the most important drivers of declining NBP and increasingly its variability. Our results show that increasing regional NBP variability can be mostly attributed to climate change.
How to cite: Fernández-Martínez, M., Peñuelas, J., Chevallier, F., Ciais, P., Obersteiner, M., Rödenbeck, C., Sardans, J., Vicca, S., Yang, H., Sitch, S., Friedlingstein, P., Arora, V. K., Goll, D., Jain, A. K., Lombardozzi, D. L., and McGuire, P. C.: Is destabilisation risk increasing in land carbon sinks?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2813, https://doi.org/10.5194/egusphere-egu23-2813, 2023.
Timely, fine-grained gridded carbon emission datasets are particularly important for global climate change research. Often, fine-grained datasets are challenging to visualize over the globe, and clear visualization tools are also needed. Therefore, we present a near-real-time global gridded daily CO2 emissions dataset (GRACED). GRACED provides gridded CO2 emissions at a 0.1° × 0.1° spatial resolution and 1-day temporal resolution from cement production and fossil fuel combustion over seven sectors, including power, industry, residential consumption, ground transportation, domestic aviation, international aviation, and international shipping. GRACED is prepared from the near-real-time daily national CO2 emissions estimates (Carbon Monitor), multi-source spatial activity data and satellite NO2 data for time variations of those spatial activity data. Here, we examined the spatial patterns of sectoral CO2 emission changes from January 1, 2019, to December 31, 2021. In 2021, most regions showed rapid rebounds in carbon emissions compared with 2020, reflecting the continuing challenges to accelerate climate mitigation in the post-COVID era. GRACED provides the most timely and more refined overview than any other previously published datasets, which enables more accurate and timely identification of when and where fossil CO2 emissions have rebounded and decreased as the world recovers from COVID-19 and witnesses contrasted efforts to decarbonize energy systems. Uncertainty analysis of GRACED gives a grid-level two-sigma uncertainty of value of ±19.9%, indicating the reliability of GRACED was not sacrificed for the sake of higher spatiotemporal resolution that GRACED provides. In addition, we also examined the distribution of emission in a grid-wise perspective for major emission datasets, and compared it with GRACED. The similarity in emission distribution was observed in GRACED and other datasets. One of the advantages of our dataset is that it provides worldwide near-real-time monitoring of CO2 emissions with different fine spatial scales at the sub-national level, such as cities, thus enhancing our comprehension of spatial and temporal changes in CO2 emissions and anthropogenic activities. With the continued extension of GRACED time series, we present crucial daily-level input to analyze CO2 emission changes in the post-COVID era, which will ultimately facilitate and aid in designing more localized and adaptive management policies for the purpose of climate change mitigation in the post-COVID era.
How to cite: Dou, X., Liu, Z., Ciais, P., Hong, J., Chevallier, F., Wang, Y., Yan, F., Davis, S. J., Crippa, M., Janssens-Maenhout, G., Guizzardi, D., Solazzo, E., Song, X., Huo, D., Ke, P., Wang, H., and Deng, Z.: Near-real-time global gridded daily CO2 emissions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3303, https://doi.org/10.5194/egusphere-egu23-3303, 2023.
Keeping global warming in line with the Paris Agreement requires rapid reductions in CO2 emissions. Tracking these reductions demands a thorough bookkeeping of natural and anthropogenic carbon fluxes. The second REgional Carbon Cycle Assessment and Processes (RECCAP2) activity of the Global Carbon Project aims to accurately assess land and ocean CO2 sources and sinks through the efforts of hundreds of scientists around the globe.
For the ocean component, regional budgets are developed for the global ocean and five large regions for the period 1980-2018. In addition, four ‘special focus’ themes, namely the biological carbon pump, the seasonal cycle, the coastal ocean and model evaluation are addressed. We use state-of-the-art ocean models and observation-based datasets to provide robust estimates of regional CO2 budgets and constrain their uncertainties. Here, we will provide an overview of RECCAP2 activities, and showcase key results focusing on mean ocean carbon fluxes, and their trends and variability.
How to cite: Hauck, J., Gruber, N., Ishii, M., and Müller, J. D. and the RECCAP2 ocean chapter leads: Constraining regional and global ocean carbon fluxes in RECCAP2, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12786, https://doi.org/10.5194/egusphere-egu23-12786, 2023.
The RECCAP2 global ocean project provides an assessment of the mean, trends, and variability of the global ocean carbon sink for the period 1985-2018. The analysis is based on a comprehensive assessment of models and observation-based products, including global ocean biogeochemical models (GOBMs), pCO2 observation-based air-sea CO2 flux products, ocean data assimilation models, and DIC-observation based products. We find that the mean ocean CO2 sink from 1985-2018 is -1.7±0.3 PgC yr-1 as diagnosed by pCO2-observation based air-sea CO2 flux products. The dominant component of the global air-sea CO2 flux is the oceanic uptake of anthropogenic CO2, which is estimated at between -2.0 to -2.6 PgC yr-1 using a range of GOBMs, assimilation models and DIC-based products. The second largest component of the global air-sea CO2 flux is the outgassing of terrestrially-derived CO2, which is estimated at 0.65±0.3 PgC yr-1 but is not yet fully resolved by RECCAP2 models. The trend in the global air-sea CO2 flux from 1985-2018 ranges from -0.26 PgC yr-1 decade-1 in the GOBMs to -0.39 PgC yr-1 decade-1 in the pCO2 products. Over the 2001-2018 period, when the pCO2-based estimates benefit from improved data coverage, they predict a strengthening trend in the ocean carbon sink of -0.63 PgC yr-1 decade-1. This is driven primarily by the trend in anthropogenic carbon uptake of -0.41 PgC yr-1 decade-1, and secondarily by a climate-forced trend of -0.28 PgC yr-1 decade-1. This climate-forced strengthening of the ocean carbon sink since 2001 is not diagnosed in the GOBMs, and the reasons for this trend remain unclear. We find that the interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2-3 times. GOBMs suggest that the climate-driven variability is about 4-8% of the global mean carbon sink, while the climate-driven variability is about 9-14% of the global mean flux in the observation-based pCO2 products. In all, the RECCAP2 analysis provides a state-of-the-art summary of our current knowledge of the ocean carbon sink, and the mechanisms driving its magnitude, trends, and variability over time.
How to cite: DeVries, T., Yamamoto, K., and Wanninkhof, R. and the RECCAP2 Global Ocean Team: Magnitude, trends, and variability of the global ocean carbon sink from 1985-2018, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16842, https://doi.org/10.5194/egusphere-egu23-16842, 2023.
The dynamic and thermohaline characteristics of the Atlantic Ocean linked to the Atlantic Meridional Overturning Circulation (AMOC) give it a specific role in the accumulation of heat and CO2, either of natural or anthropogenic origin (Cant), from the surface layer to the deep waters, significantly mitigating the impacts of anthropogenic climate change. Here, we evaluate the annual mean, long-term trends, seasonal cycle and interannual variability of net sea-air CO2 fluxes (FCO2) between 1985 and 2018 based on observation products (pCO2-products) and global ocean biogeochemical models (GOBMs) for the Atlantic from 30ºS to the Nordic Seas (~79ºN) and the Mediterranean. The mean contemporary FCO2 (sum of anthropogenic and natural components) is estimated to be 0.362 ± 0.067 and 0.47 ± 0.15 Pg C yr-1 using pCO2-products and GOBMs, respectively. The GOBMs show consistent growth trends in CO2 uptake with rates similar to the atmospheric CO2 growth, however trends obtained from CO2-products show a sharp increase from the pre-2000 period to the post-2000 period. There is overall agreement between pCO2-products and GOBMs results for mean values, seasonal cycle and interannual variability in all biomes, except for the North Atlantic subpolar biome, where pCO2-products show lower mean values, larger trends, and a different seasonal cycle than GOBMs. The GOBMs and pCO2-products show very concordant values in equatorial and subtropical regions, where CO2 variability is strongly determined by temperature. For the period 1994-2007, GOBMs show concordant values in annual Cant storage rate with carbonate marine system observations (Gruber et al., 2019) with values of 0.506 ± 0.106 Pg C yr-1 vs 0.673 ± 0.066 Pg C yr-1, respectively. The Cant storage rate agreement between GOBMs and observations are also registered in the different biomes, although in both permanently stratified subtropical in North and South Atlantic biomes, the storage rates in GOBMs show a larger spread with their mean values 30 and 40% lower than those estimated from observations. In general, the Atlantic accumulates more Cant than that inferred from the cumulative FCO2 changes, partly due to a significant lateral Cant transport from the Southern Ocean (about 30%).
How to cite: Perez, F. F., Gehlen, M., Tjiputra, J., Olsen, A., Becker, M., Lopez-Mozos, M., Müller, J. D., Goris, N., and Hauck, J.: An assessment of CO2 storage and sea-air fluxes for the Atlantic Ocean and Mediterranean Sea between 1985 and 2018 , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13759, https://doi.org/10.5194/egusphere-egu23-13759, 2023.
Cool temperatures, vigorous overturning circulation, and high biological productivity make the Southern Ocean a key region for the air-sea CO2 exchanges. It is also the main gateway for anthropogenic CO2 into the ocean owing to the upwelling of old water masses with low anthropogenic CO2 concentration, and the transport of the newly equilibrated surface waters into the ocean interior. Here we present results from the Southern Ocean chapter of RECCAP2, which is the Global Carbon Project’s second systematic study on Regional Carbon Cycle Assessment and Processes. We analyse Southern Ocean contemporary carbon fluxes and anthropogenic carbon accumulation in 1985-2018 from a wide range of global ocean biogeochemical models (GOBMs), surface ocean pCO2-based data products (pCO2-products), and data-assimilated models, with the aim of identifying patterns of regional and temporal variability, model limitations and future challenges. Our results highlight agreement of GOBMs and pCO2-products on the mean Southern Ocean contemporary CO2 uptake (0.75 ± 0.28 PgC yr-1 and 0.74 ± 0.07 PgC yr-1 respectively). Compared with RECCAP1 (where the database of model- and observation-based estimates was significantly smaller), the new estimates suggest a weaker sink, possibly due to better representation of winter outgassing. Strong discrepancies exist between GOBMs and pCO2-products in seasonality and trend estimates between 1985-2018. The pCO2-products show the presence of a stagnation in uptake through the 1990’s followed by a rapid increase in uptake, while GOBMs show consistent uptake throughout the 1985-2018 period. On a regional level, the subtropical seasonally stratified (STSS) biome has the largest air-sea CO2 flux with uptake of CO2 peaking in winter, whereas the ice (ICE) biome is characterised by a generally small magnitude of fluxes into and out of the ocean and a pronounced seasonal cycle with the largest ocean uptake of CO2 in summer. Connecting these two, the subpolar seasonally stratified (SPSS) biome has intermediate flux magnitude, with GOBMs showing spread in the strength of winter outgassing and difficulties in simulating the strongest CO2 uptake in summer. The biases in GOBMs originate mainly from the non-thermal component of air-sea CO2 flux, and in particular from the difficulty in simulating the competing effects of circulation and biology on carbon draw-down in summer. Our analysis reveals a distinct zonal asymmetry (secondary to the latitudinal gradient) between the Atlantic, Pacific and Indian sectors. The zonal asymmetry is observed in the mean uptake and amplitude of the seasonal cycle rather than the phasing of the seasonal cycle. GOBMs show a 20% spread and an overall underestimate of their simulated anthropogenic carbon accumulation, pointing to insufficient water mass formation and interior ventilation. These first results confirm the global relevance of the Southern Ocean carbon sink and highlight the strong regional and interannual variability of the Southern Ocean carbon uptake in connection to physical and biogeochemical processes.
How to cite: Patara, L., Hauck, J., and Gregor, L. and the RECCAP2 Southern Ocean team: RECCAP2 – Southern Ocean carbon fluxes and storage, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17328, https://doi.org/10.5194/egusphere-egu23-17328, 2023.
Here we present a synthesis of surface ocean pCO2 and air-sea CO2 flux seasonality for a modern climatology and their decadal trends between the 1980s and 2010s, as part of the REgional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project. Working with both surface ocean pCO2-observation products (pCO2 products) and global ocean biogeochemistry models (GOBMs), our main findings are: (i) Over biome scales, both pCO2 products and GOBMs confirm increases in the seasonal amplitude of pCO2 and integrated CO2 fluxes between 1985-1989 and 2014-2018. (ii) For the 2014-2018 climatology, GOBMs exhibit a systematic bias with too-weak biologically-driven seasonal variability in surface dissolved inorganic carbon (DIC), such that the pCO2 seasonal cycle in subtropical biomes is spuriously large and both the amplitude and phase of seasonal pCO2 variations diverge from those in the pCO2 products in subpolar and circumpolar biomes. (iii) Decadal increases in pCO2 seasonal cycle amplitude in subtropical biomes are attributed to being largely driven by reducing CO2 buffering capacity and increasing sensitivity to temperature due to increasing anthropogenic carbon (Cant) content insurface waters for both the pCO2 products and GOBMs. In subpolar and circumpolar biomes, the seasonality change for GOBMs is dominated by Cant invasion, whereas for pCO2 products modulations of the climate state are equally important. (iv) Considered together, the subtropical biomes exhibit decadal increases in CO2 flux seasonality that are larger during winter than summer, consistent with the mechanism described by Fassbender et al. (2022) and potentially promoting a negative feedback in the climate system by increasing the CO2 uptake in winter, by virtue of surface winds being stronger in winter than summer. (v) Large ensemble simulations with ESMs were applied to confirm the validity of biomes as aggregation domains for identifying forced signals. Despite compromises to DIC seasonality impacting pCO2 seasonality, the chosen biome-scale is appropriate for representing the decadal rate of increase of pCO2 seasonality for both GOBMs and pCO2 products.
How to cite: Rodgers, K. and the RECCAP2 coauthors: seasonal variabiltiy in surface ocean carbon cycle: Seasonal variabiltiy of the surface ocean carbon cycle: a global synthesis, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10894, https://doi.org/10.5194/egusphere-egu23-10894, 2023.
Around 31% of carbon dioxide derived from human activities (Canth) has been absorbed by the ocean (DeVries, 2014; Gruber et al., 2019; Sabine et al., 2004). This accumulation helps to mitigate atmospheric carbon dioxide (CO2), but in turn leads to severe consequences on marine systems (IGBP, IOC, SCOR, 2013). Both components of CO2, i.e. anthropogenic and natural, present high variability and uncertainties difficult to observe and quantify. In particular, the Canth signal represents a small fraction of the total dissolved inorganic carbon pool (CT) and it is not directly distinguishable from the natural component, resulting in the emergence of back-calculation techniques (Brewer 1978; Chen and Millero, 1979) to derive it indirectly. Over the years, back-calculation techniques have undergone remarkable improvements (Gruber et al., 1996; Sabine et al., 2004; Touratier et al., 2004, 2007; Vázquez-Rodríguez et al., 2009a, 2009b, 2012), resulting in different methods for estimating Canth that, despite providing helpful and advanced results, show various biases and limitations. Here, we present a new approach for estimating Canth that relies on a back-calculation methodology, purely based on carbon data, and provides results that show good agreement with previous global Canth climatologies. Our approach mainly differs from previous methodologies by pioneering using the transport matrix output from a data‐assimilating ocean circulation inverse model (TMI: Total Matrix Intercomparison; Gebbie and Huybers, 2010) to obtain preformed properties, instead of the historical use of Optimum Multiparameter analysis (OMP). This improvement prevents from the need to use (sub)surface-property linear regressions to estimate preformed alkalinity or air-sea CO2 disequilibrium, and allows introducing different corrections for denitrification and, as a novelty, oxygen disequilibrium.
How to cite: López-Mozos, M., Pérez, F. F., Carracedo, L. I., Gebbie, G., and Velo, A.: A new approach for estimating anthropogenic carbon relying on an observational back-calculation method, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15146, https://doi.org/10.5194/egusphere-egu23-15146, 2023.
This contribution presents a new view of the global carbon cycle which accounts for the land-to-ocean transport of carbon through inland waters, estuaries, tidal wetlands and continental shelf waters—the ‘land-to-ocean aquatic continuum’ (LOAC). We highlight how biogeochemical and ecological processes from land-to-ocean have been perturbed by human interventions, including atmospheric composition change, climate change and land-use change. The extend to which these anthropogenic perturbations have altered regional and global CO2 budgets and trends along the LOAC are also presented and the knowledge gaps that are key to reduce uncertainties in future assessments of LOAC fluxes are identified. Finally, broader implications regarding the quantification of the terrestrial and open ocean sinks of anthropogenic carbon are briefly discussed
How to cite: Regnier, P., Resplandy, L., Rosentreter, J., Najjar, R., and Ciais, P.: The land-to-ocean loops of the global carbon cycle: How much do we know about long-term trends and drivers of changes in CO2 fluxes ?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16001, https://doi.org/10.5194/egusphere-egu23-16001, 2023.
Inland waters are important sources of the greenhouse gasses (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) to the atmosphere. While a growing number of global estimates of inland water GHG emissions exists, the integration of inland waters into regional GHG budgets is often hampered by the lack of adequate geo-spatial datasets. Moreover, existing estimates diverge substantially, in part due to persisting uncertainties related to the size and distribution of effective inland water surface areas. In the framework of the 2nd phase of the REgional Carbon Cycle Assessment and Processes (RECCAP-2) initiative, we synthesize existing estimates of GHG emissions from streams, rivers, lakes and reservoirs, and homogenize them with regard to underlying global maps of inland water surface areas and the effects of seasonal ice cover. We then produce estimates of inland water GHG emissions for 10 extensive land regions that are used for the regional land budgets of RECCAP2. According to our synthesis, global inland waters emit 5.6 (3.5-9.1) Pg CO2 yr-1, 101 (83-135) Tg CH4 yr-1 and 326 (254-592) Gg N2O yr-1. South American rivers contribute about one third of global inland water CO2 emissions. North-American and Russian lakes contribute together one third of global inland water CH4 emissions. Finally, North America alone contributes one fourth of global inland water N2O emissions.
The global inland water emissions sum up to a global warming potential (GWP) of an equivalent emission of 13.6 (10.0-20.3) and 8.3 (5.8-12.7) Pg CO2 yr-1 at a 20- and 100-year horizon, respectively. At 100-year horizon, the contribution of CO2 dominates the GWP of global inland water GHG emissions, with rivers being the largest emitters. At the 20-year horizon, on the contrary, lakes and rivers are equally important emitters, and the contributions of CH4 to the GWP of inland water GHG emissions even exceed those of CO2. Contributions of N2O to the GWP appear to be less significant at both time horizons. Normalized to the area of the RECCAP-2 land regions, South America and South East Asia show the highest inland water emission rates in terms of GWP, dominated by riverine CO2 emissions.
How to cite: Lauerwald, R., Allen, G. H., Deemer, B. R., Liu, S., Maavara, T., Raymond, P., Alcott, L., Bastviken, D., Hastie, A., Holgerson, M. A., Johnson, M. S., Lehner, B., Lin, P., Marzadri, A., Ran, L., Tian, H., Yang, X., Yao, Y., and Regnier, P.: Synthesis, homogenisation and regionalisation of inland water greenhouse gas budget estimates for the RECCAP2 initiative, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1333, https://doi.org/10.5194/egusphere-egu23-1333, 2023.
Posters on site: Mon, 24 Apr, 16:15–18:00 | Hall A
India is primarily concerned with comprehending regional carbon source-sink response in tandem with changes in atmospheric carbon dioxide (CO2) concentrations or human-caused anthropogenic emissions. Atmosphere CO2 is the most significant greenhouse gas contributing to climate change and global warming. To develop a countrywide mitigation policy, it is therefore critical to identify underlying source-sink locations and their mechanisms at various temporal scales and regional levels. To better understand the variability of CO2 and its relationship with the climate variables requires long-term observations. Recent advancements in high-resolution satellite measurements provide a viable opportunity to examine CO2 variability at a regional level. In this work, we presented the long-term variations and growth rates of the Greenhouse Gas Observing Satellite (GOSAT) and Orbiting Carbon Observatory-2 (OCO-2) satellite retrieved column-averaged dry-air mole fraction of CO2 (XCO2 ) and the relationship of XCO2 growth rate with ENSO and climate parameters (temperature, precipitation, soil moisture, and NDVI) over India for the period 2010 to 2021. Results revealed an increase of 2.54 (2.43) ppm/yr of XCO2 in GOSAT (OCO-2) retrievals during overlapping measurement period (2015-2021). In addition, a wavelet analysis shows an increase in XCO2 every year for GOSAT; however, OCO-2 decreases and increases in XCO2 every 5-6 months. This is attributable to high resolutions measurements of OCO-2 favouring better capture of source (high XCO2)-sink (low XCO2) signal than GOSAT. The Principal Component Analysis (PCA) analysis on XCO2 anomalies showed EOF-1 contributed mainly by the south and southeast of India. Further analysis demonstrated that the trend and seasonal cycle of XCO2 regulates the variability. The XCO2 growth rates strongly correlate with ENSO and NDVI (clear during major ENSO events), whereas precipitation and temperature show a weak correlation. Further, lag correlation analysis reveals that ENSO and climate parameters precede the GOSAT XCO2 growth rates, with soil moisture, NDVI, and ENSO having a good correlation with 8,4 and 3 months of leads, respectively.
How to cite: Das, C. and Kunchala, R. K.: Understanding long-term carbon dioxide (CO2) variability and its link with ENSO and climate parameters over India using satellite retrievals, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4738, https://doi.org/10.5194/egusphere-egu23-4738, 2023.
In Australia, increasing temperatures and prolonged drought periods lead to an intensification of wildfires. In particular, severe fires are expected to occur more frequently in Southeast Australia’s eucalyptus forests leading to strongly enhanced CO2 emissions and preventing the renewed uptake of the released CO2 by vegetation. However, current fire emission estimates presented by conventional fire emission databases show significant discrepancies in their emission estimates of extreme fire events like the Australian fire season 2019/2020.
Here, we investigate the fire emissions released during the Australian summer 2019/2020 based on total column measurements of CO2 and CO using the Lagrangian Particle Dispersion Model FLEXPART. We calculate footprints and backward trajectories of trace gases to inversely retrieve carbon emission estimates. In a first case study we focus on TCCON total column measurements of CO and CO2 taken in Wollongong located close to the hot-spot of eucalyptus fires. As the measurements show a significant enhancement of all mentioned tracers during the fire event, FLEXPART is used to calculate emission estimates for southeast Australia. Furthermore, we retrieve emission factors between the trace gases. Our results are compared to the conventional databases like GFED, GFAS and FINN and emission estimates published by other studies.
How to cite: Dillerup, I., Lüken-Winkels, C., Metz, E.-M., Vardag, S., Deutscher, N., Griffith, D., and Butz, A.: Fire emission estimates for Australian extreme fire season 2019/2020 using FLEXPART , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12203, https://doi.org/10.5194/egusphere-egu23-12203, 2023.
Methane (CH4) has a relatively long tropospheric lifetime and is consequently a well-mixed greenhouse gas. CH4, released by several
types of human activity and natural processes, is one important driver of climate change. The global mean concentration of CH4 has
increased by 156% between the beginning of the industrial revolution around 1750 and 2019, reaching roughly 1866 ppb in 2019 (IPCC).
The time dependence of this increase is not well understood. For example, it is not entirely clear why CH4 growth rates reached record
high values in 2020 and 2021. Furthermore, the number of published growth rates (annual methane increases) is limited and includes data
from NOAA and the Copernicus Climate Change Service. Hence the rate of increase of CH4 calculated from independent data sources are
valuable for cross-verification and in furthering our understanding of the methane cycle.
The TROPOMI instrument onboard the Sentinel-5P satellite provides daily CH4 data with a spatial resolution of roughly 7x7 km²
and global coverage. We analyze the TROPOMI CH4 data with the goal of determining robust values of the annual methane increases (AMI)
for both global and zonally resolved data. For this we utilize a dynamic linear model approach to separate the underlying methane level,
the seasonal and short-term variations. The AMIs are defined as the difference in the underlying (i.e. fitted) methane level between
the first and last day of a year. In this contribution, we present first results for global and zonal TROPOMI AMIs for the years 2019-2022.
We compare the resulting global TROPOMI AMIs with data from NOAA and Copernicus and discuss the distribution of zonal AMIs for the given years.
How to cite: Hachmeister, J., Schneising, O., Buchwitz, M., Burrows, J. P., Notholt, J., and Buschmann, M.: Recent methane trends derived from S5P/TROPOMI data, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11303, https://doi.org/10.5194/egusphere-egu23-11303, 2023.
The use of δ2H as well as δ13C methane isotope measurements will help improve regional and global source apportionment and understanding of reasons for methane’s continued and accelerating growth. However more data on regional variability in isotopic signatures of the main sources is required as well as regular measurements of both isotopes in methane in background air.
Field campaigns across Canada in June 2022 and to northern Finland and Norway in August 2022 were carried out to collect air samples for methane δ13C and δ2H isotopic characterisation from boreal wetlands.
In Finland and Norway a road campaign with continuous measurements of methane mole fraction was carried out from Södankyla, Finland to Aidejavri, Norway, with a generally decreasing gradient in methane from south to north and this has been compared with land cover maps. Air samples for isotopic analysis were collected at Södankyla, Kaamanen and Lompolojänkkä fens in Finland and Aidejavri and Suossjavri degrading palsa mires in Norway. In Canada δ2H and δ13C isotopic signatures were determined in methane emitted by wetlands in northern Ontario including at Fraserdale, and northern Saskatchewan (East Trout Lake).
Overall the mean signatures of emissions from the boreal samples collected were -67‰ for δ13C and -320‰ for δ2H, but there was significant local variability when sampling air close to ground level. Aircraft campaigns would be a better way of identifying the integrated isotopic signature of regional wetland emissions (as demonstrated previously for δ13C signatures across northern European wetlands). Weekly sampling for methane δ13C and δ2H was started at Pallas Sammaltunturi in northern Finland in August 2022. These data will be used to identify the regional source signature of emissions.
How to cite: Fisher, R., Woolley Maisch, C., Lowry, D., France, J., Rockmann, T., van der Veen, C., Fowler, C. M. R., and Nisbet, E. G.: Measurement of the isotopic signature of boreal wetland methane emissions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16482, https://doi.org/10.5194/egusphere-egu23-16482, 2023.
The global atmospheric CH4 growth rate stagnated between 2000 and 2007, and has continued to grow since 2007. This renewed CH4 rise has been analysed with respect to a 2007 onward decline in δ13C(CH4), indicating changes in the relative contribution of CH4 sources. However, this is still subject to debate and a variety of hypotheses have been put forward. In our work, we present numerical sensitivity simulations that investigate the impact of different inventories of methane emission fluxes on the globally averaged δ13C(CH4) signature. We apply the state-of-the-art global chemistry-climate model EMAC and use a simplified approach to simulate methane loss. We include methane isotopologues and take the kinetic isotope effects in physical and chemical processes into account. We further consider regional differences in the isotopic signatures of individual emission source categories, such as, for example, the differences between signatures of tropical and boreal wetlands emissions. Based on recent emission inventories and isotopic source signatures from the literature, our chemistry climate model reproduces the actual atmospheric methane and δ13C(CH4) distribution adequately. We show that our setup is suitable to constrain the individual influence of different CH4 sources on the global average δ13C(CH4). We further present an approach to optimize the global methane level with respect to station measurements probing for a strategy to include the isotopic information into such an optimization process.
How to cite: Nickl, A.-L., Winterstein, F., and Jöckel, P.: Numerical simulation of the atmospheric CH4 increase and the corresponding decrease of δ13C(CH4) after 2007, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14171, https://doi.org/10.5194/egusphere-egu23-14171, 2023.
The growth rate of atmospheric CO2 mole fractions can be measured with high accuracy, but there are still large uncertainties in our ability to separate anthropogenic and natural sources and sinks. One major source of uncertainty is the net flux of carbon from the biosphere to the atmosphere, or Net Ecosystem Exchange (NEE). There are two major approaches to quantifying NEE; top-down approaches that typically use atmospheric inversions, and bottom-up estimates using process-based or data-driven terrestrial biosphere models, upscaled to the regional or global scale. Both approaches have known limitations. A system that harmonizes these approaches, providing a high-quality estimate of the spatial distribution of NEE, and an accurate integral of NEE at regional and global scales, would improve our ability to model the full carbon budget. With other component fluxes, a harmonized product could help improve our monitoring of regional and national greenhouse gas budgets, and thus verify the trajectory towards CO2 emission goals.
This study builds upon our previous work that connected the bottom-up eddy-covariance model to top-down estimates of regional NEE from atmospheric inversions using fixed regional linear oper-ators. That work demonstrated that top-down estimates of atmospheric CO2 provide an important additional constraint to a data-driven bottom up model. The use of top-down constraints improved the regional and global upscaling of NEE, leveraging the strengths of the two different approaches. However, the previous work had a simplified computational link between the top-down and bottom-up fluxes of NEE, and did not access the very large volume of atmospheric observations of atmospheric CO2. Here, we replace the regional atmospheric inversion estimates of NEE with direct observations of the atmospheric mole fractions of CO2. The fixed regional linear operators are replaced by estimating the near-field sources of an observation using an atmospheric transport model. For training, the bottom-up model is run for the source locations. We apply this technique to observations from to tropical, extra-tropical and boreal tall-tower sites over different meteorological conditions where we infer NEE from the observed atmospheric mole fraction, corrected for CO2 background and non-biogenic CO2 fluxes. This inference is combined in the objective function with tower-level inferences, and directly used to update the bottom-up model. The model can ‘see’ more varied inputs in the dynamic footprints, and the size of our pool of training data is increased. The new process improves our ability to accurately infer the regional and global distribution of NEE by directly learning across spatial scales, using diverse observations of CO2.
How to cite: Upton, S., Peters, W., Reichstein, M., Botia, S., Gans, F., Kraft, B., and Bastos, A.: Constraining land surface CO2 fluxes by ecosystem and atmospheric observations using atmospheric transport, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12424, https://doi.org/10.5194/egusphere-egu23-12424, 2023.
As one of the most sensitive regions to climate change on the Earth's surface, the Qinghai-Tibet Plateau is experiencing lasting warming, which has been evidenced to enhance surface carbon uptake but also could lead to carbon emission due to accelerated permafrost degradation and ecosystem respiration. Due to the difficulties of limited observations and imperfect modeling techniques, whether the Qinghai-Tibet Plateau is a carbon sink or source has been an ongoing debate. The recent satellite XCO2 Observations could provide some useful constraints on the carbon budget in this region. Here, based on the recent OCO-2 XCO2 observations and the inversion results from the OCO-2 v10 MIP, we estimated the net biome carbon fluxes for the Qinghai-Tibet Plateau. Our results suggest that this region has become a carbon source (around -0.10 PgC/year) already, which is supported by an upscaling estimate with intensified eddy covariance flux measurements over China. Meanwhile, we found this carbon source signal is not detected by either in-situ CO2 inversions or terrestrial biosphere model simulations. Currently, although some studies based on flux measurements report this region is a carbon sink and even keeps increasing recently, many others hold opposite viewpoints about it. Our result provides an important piece of evidence supporting that the Qinghai-Tibet Plateau becomes a carbon source, albeit additional evidence is needed, especially from in-situ CO2 observations and aerial CO2 observations (e.g., by aircraft, unmanned aerial vehicle, and AirCore). In principle, atmospheric CO2 measurements could provide a more complete picture of the carbon budget in this region compared to discrete and limited eddy flux measurements. In the future, enhanced in-situ and aerial CO2 observations are expected to disentangle the puzzle of this carbon budget issue in this region.
How to cite: He, W., Jiang, F., Ju, W., Wang, H., Nguyen, N. T., and Chen, J. M.: The Qinghai-Tibet Plateau may have already shifted to carbon source: Evidence from OCO-2 satellite XCO2 observations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1609, https://doi.org/10.5194/egusphere-egu23-1609, 2023.
Determining the temperature dependence of wetland CH4 and CO2 emissions is critical for predicting the impacts of climate change on greenhouse gas (GHGs) emissions in wetland ecosystems. However, the spatial variation for temperature dependence of wetland CH4 and CO2 emissions is poorly understood, especially at the global scale. Here, we investigate the temperature dependencies of wetland CH4 and CO2 emissions across large-scale climatic gradients using 56,271 daily paired observations of ecosystem-level CH4 and CO2 emissions in 45 widely distributed wetlands from the FLUXNET-CH4 database. The temperature dependencies of CH4 and CO2 emissions show contrasting spatial patterns across globally geographic climate gradients. Specifically, the temperature dependence of CH4 emissions increased with increasing mean annual temperature (MAT), but the opposite was true for that of CO2 emissions. The ratio of CH4 to CO2 emissions was positively dependent on temperature when only MAT and mean annual precipitation were greater than 4.7 °C and 483 mm, respectively. Our results imply that the relative contribution of CH4 to total GHG emissions increases with ambient temperature increases in a warmer and wetter climate region and could act as a positive feedback mechanism in the future.
How to cite: Chen, H. and Zhou, X.: Contrasting patterns in the temperature dependence of wetland CH4 and CO2 emissions across globally geographic climate gradients, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4684, https://doi.org/10.5194/egusphere-egu23-4684, 2023.
Despite the urgent need for reduction of greenhouse gas concentrations, their emissions remain at high levels worldwide. Atmospheric inverse modelling allows to quantify these emissions by leveraging observations of greenhouse gas mole fractions and chemistry-transport models. However, this technique largely relies on models with an imperfect representation of transport and chemical processes and the resulting errors propagate to emission estimates. Atmospheric scientists can improve their models by comparing simulated processes against available observational data.
One efficient, although challenging, way of acquiring such validation data is to perform a tracer release experiment. It consists of releasing one or multiple decaying tracers into the atmosphere at one or multiple locations in the world, and then observe their time-evolving mixing ratios to understand transport pathways, mixing and decay rates. To the best of our knowledge, tracer release experiments have only been performed at local or regional scales to study transport processes, but never at the global scale. A global tracer release experiment could generate invaluable data against which to compare model outputs. However, modelers must be able to disentangle transport and chemical processes from the data, which requires that the experiment be carefully designed. Subject to this requirement being met, it could help to better quantify and even reduce 1) transport errors by investigating inter- and intra-hemispheric transport and 2) chemistry errors by constraining OH tropospheric concentrations. These data could also help to create a benchmarking methodology to highlight the strengths and weaknesses of the regional and global models that are currently used to quantify greenhouse gas emissions.
Here, we present design considerations for such a global tracer release experiment based on simulations with the 3-D chemistry-transport model ICON-ART. Our first results indicate that releasing several hundred tons of two tracers with different lifetimes as pulses could be sufficient to obtain a good estimate of OH concentrations along the parcel trajectories. This method could be applied at different locations in order to sample a large part of the world and at different times, e.g., to account for seasonal variations in OH concentrations. However, we also show that many parameters influence the results and therefore we enumerate the benefits but also the limits of such an experiment.
How to cite: Thanwerdas, J., Brunner, D., and Henne, S.: A global tracer release experiment to help estimate OH tropospheric concentrations and benchmark chemistry-transport models, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5420, https://doi.org/10.5194/egusphere-egu23-5420, 2023.
An increasing trend is observed in the frequency of climate extremes. Drought is a widely observed extreme event that has a significant influence on the terrestrial ecosystem functioning and carbon balance. Interannual variability in the Indian summer monsoon (ISM) rainfall, an important meteorological phenomenon providing 90 percent of the country’s annual precipitation, also significantly influences the vegetation carbon processes and carbon balance. Identifying the changes in vegetation greenness and terrestrial carbon fluxes to droughts and variability in ISM is essential for planning mitigation strategies and policy making. The main objective of this study is to identify the impact of drought and ISM variability in terrestrial biosphere carbon processes and their impact on the national carbon budget. Here we attempt a comprehensive study using different meteorological datasets available and CO2 flux data prescribed from inversion, process-based, and LUE-based models to quantify the impact of extreme events and monsoonal variability on the ecosystem behavior and, thereby, on the atmosphere-biosphere CO2 exchange fluxes over the Indian region while considering prominent vegetation classes. We also use the inference from the satellite-derived Solar Induced Fluorescence (SIF) and eddy covariance flux observations over the region. Preliminary results will be presented and discussed.
How to cite: Ravi P, A. and K Pillai, D.: Assessing the impact of climate extremes and Indian summer monsoon variability on terrestrial biosphere carbon fluxes over Indian region using satellite observations and modeling., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10881, https://doi.org/10.5194/egusphere-egu23-10881, 2023.
The number of in-situ CO2 measurements in the Southern Hemisphere is very limited. This leads to large
uncertainties in estimates of regional carbon fluxes by in-situ based inverse models. Satellite-based CO2
measurements, on the other hand, are available in the Southern Hemisphere with a dense spatial
coverage. By evaluating these, the regional carbon cycle can be studied in more detail and the results of
carbon cycle models can be validated against the satellite data.
Here, we present a comparison of atmospheric CO2 data provided by the Greenhouse gases Observing
SATellite (GOSAT) and in-situ based inverse models for South America from 2009 to 2019. The seasonal
cycle of atmospheric CO2 concentrations measured by the GOSAT satellite shows differences in both,
amplitude and timing, compared to in-situ based atmospheric inversions. To determine the reason for
these discrepancies, we use the TM5-4DVar atmospheric inversion model assimilating GOSAT satellite
data to obtain GOSAT based land-surface fluxes. This allows us to identify sub-regions responsible for the
differences. In order to gain a deeper understanding of the underlying processes, we also analyse various
climate parameters, fire emission data, and vegetation proxies (for example Solar Induced Fluorescence,
SIF). By doing so, we aim at improving our understanding of the mechanisms that influence the seasonal
carbon cycle in South America.
How to cite: Artelt, L., Metz, E.-M., Vardag, S., Basu, S., and Butz, A.: The seasonal cycle of atmospheric CO2 in South America over the last ten years seen by GOSAT, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6152, https://doi.org/10.5194/egusphere-egu23-6152, 2023.
Climate change mitigation requires – besides greenhouse gas emission reductions – actions to increase carbon sinks and storages in terrestrial ecosystems. However, quantification of sources and sinks of carbon depends on reliable estimates of the net ecosystem exchange of carbon dioxide (CO2). This also involves the eddy covariance technique (EC), a key method to directly measure the CO2 fluxes between ecosystems and the atmosphere. Various methods have been used to impute, or gap-fill, missing EC data and previous comparisons have shown that the accuracy of the best-performing methods, e.g. the widely-used marginal distribution sampling (MDS), is reaching the noise limit of measurements. However, knowledge on the performance of gap-filling methods is lacking from northern ecosystems.
By analyzing an extensive global data set, we show that MDS causes significant carbon balance errors for northern ecosystems. MDS systematically overestimates the carbon dioxide (CO2) emissions of carbon sources and underestimates the CO2 sequestration of carbon sinks. We discuss reasons for the errors and show how a machine learning method called extreme gradient boosting or a modified version of MDS can be used to minimize the northern site bias.
How to cite: Vekuri, H., Tuovinen, J.-P., Kulmala, L., Papale, D., Kolari, P., Aurela, M., Liski, J., Laurila, T., and Lohila, A.: A new gap-filling method to avoid systematic bias in carbon balance estimates in northern ecosystems , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11163, https://doi.org/10.5194/egusphere-egu23-11163, 2023.
Tropical ecosystems play an important role in regulating the global carbon balance. Existing studies have extensively analyzed the carbon dynamics of tropical forests, the largest terrestrial component of the global carbon budget, showing a likely neutral contribution of tropical forests to the global carbon cycle. However, high-resolution dynamics of aboveground carbon (AGC) change of the whole tropical terrestrial ecosystem and its processes remain rarely investigated. In this study, we first used low-frequency L-band passive microwave observations to derive wall-to-wall maps of annual AGC stocks over the tropics at 25-km spatial resolution. Using high-resolution satellite observations of land-cover change and biomass maps and random forest models, we separated the AGC stock into various ecosystems, including forest, shrub, and short-vegetation (grass and crop), and attributed the change to different degradation processes such as fires and deforestation at 100-m resolution. Our preliminary results show that total AGC stocks in tropical ecosystems increased by +2.25 [+1.19,+3.29] PgC (the range represents the minimum and maximums of the multiple estimates) from 2010 to 2020. The coast of Brazilian Mata Atlantica, Central African Republic, and east Tanzania are the hotspots of net increase, while the Arc of Deforestation in the Amazon basin and the Congo Basin show substantial net losses. Gross losses from non-fire deforestation and fire totaled -1.62 [-1.38,-1.86] PgC yr-1. We also observed strong recovery in African burned regions, possibly due to post-fire regrowth and additional recovery resulting from declining fires in the region. Our results highlight the importance of explicit temporal and spatial mapping of tropical carbon dynamics at high resolution, which can help us better understand the role of tropical terrestrial ecosystems in the global carbon cycle.
How to cite: Feng, Y., Ciais, P., Xu, Y., Wigneron, J.-P., Li, X., and Fan, L.: High-resolution quantification of aboveground carbon change over the tropics, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12963, https://doi.org/10.5194/egusphere-egu23-12963, 2023.
Posters virtual: Mon, 24 Apr, 16:15–18:00 | vHall BG
As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of the Arctic Ocean CO2 uptake and their uncertainties from state-of-the-art surface ocean pCO2-observation products, global and regional ocean biogeochemical models and atmospheric inversions. For the period of 1985−2018, the Arctic Ocean represents a net sink of CO2 of 103 ± 19 TgC yr−1 in the pCO2 products and 92 ± 30 TgC yr−1 in the ocean biogeochemical models. While the long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon, it is enhanced 28% by the atmospheric CO2 increase and 15% by climate change. Moreover, the climate effect in the Arctic Ocean has become more important in recent years. The CO2 uptake peaks in late summer and early autumn, and is low in winter because the sea ice cover inhibits sea-air fluxes. The annual mean of CO2 uptake increased due to the decreasing sea ice concentration both in the pCO2 products and the ocean biogeochemical models. Both, the mean CO2 uptake and the trend, is substantially weaker in the atmospheric inversions. Uncertainty across all estimates is large especially in the estimated surface ocean pCO2 values in the East Siberian Sea and the Laptev Sea, due to scarcity of observations and missing processes in models, such as land-sea fluxes and sediment dynamics.
How to cite: Yasunaka, S., Manizza, M., Terhaar, J., Olsen, A., Yamaguchi, R., Landschützer, P., Watanabe, E., Carroll, D., Adiwira, H., Müller, J., and Hauck, J.: An assessment of sea-air CO2 flux in the Arctic Ocean from 1985 to 2018, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10462, https://doi.org/10.5194/egusphere-egu23-10462, 2023.
The oceanic uptake and release of carbon dioxide (CO2) play a critical role in global carbon cycle since oceans can act both as sink and source of CO2 which vary spatially and temporally. The ocean primary productivity has significant effects on the CO2 flux, as it consumes the dissolved CO2 at the sea surface for the photosynthetic carbon production, reducing the surface carbon content, while higher production rates at surface layers cause higher respiration rates in the subsurface layers, thereby increasing the sea water CO2 partial pressures (pCO2) in these layers. Northern Indian Ocean is found to be a perennial source of CO2 and also one of the most productive regions of Indian Ocean, however, while the western sub basin acts as an annual source, the eastern counterpart is a seasonal sink, especially during the monsoon and winter seasons. The major factors contributing to its high productivity is the summer and winter blooms caused by the wind-driven upwelling and winter cooling as well as convective mixing. The present study attempts to understand the relation between the CO2 fluxes and primary productivity in the western and eastern sub basins of the northern Indian Ocean. The study divides the Sea in to North, West, East and Central parts based on the productivity and analyses the spatial and temporal variation of the CO2 exchange between the sea and atmosphere in connection with the primary production. Satellite as well as climatological data were used to derive the monthly CO2 fluxes and ocean primary productivity. Both sub basins exhibited high rates of productivity during the monsoon and winter seasons; high monsoon and winter CO2 outfluxes were observed over the western sub basin in the northern waters towards the coast, while the eastern basin was found to have strong influxes in both the seasons over the northern waters. Towards the open ocean part, both fluxes and productivity showed decreasing trends in the western basin, whereas, the eastern sub basin showed an increasing trend of CO2 outflux over the open ocean waters in the south. Surface stratification and limited nutrient availability have resulted in the low productivity rates during the pre- and post-monsoon seasons in both basins, while the absence of the surface mixing resulting from the stratification along with photosynthetic consumption lowered the fluxes. The primary production was observed to have a significant influence over the western basin fluxes while the fluxes over the eastern basin were primarily affected by the physical forcing i.e., the thermohaline stratification.
How to cite: Krishna, L., Bharti, R., and Mahanta, C.: Significance of biological forcing on the spatio-temporal variability of carbon dioxide fluxes over the Northern Indian Ocean , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15166, https://doi.org/10.5194/egusphere-egu23-15166, 2023.
Assessing and understanding the causes of mismatches between inversion results and inventories is key to future greenhouse gas budget estimates and also a contribution to phase 2 of the REgional Carbon Cycle Assessment and Processes (RECCAP2) initiative. Here, we compare the latest greenhouse gas budgets from the updated National Greenhouse Gas Inventories (NGHGIs) submitted to the United Nations Framework Convention on Climate Change (UNFCCC) and from the updated atmospheric inversions based on both in-situ and satellite observations. We compile the latest global harmonized NGHGI database for all countries according to the updated national communications (NCs) and biennial update reports (BURs) by the end of the year 2022. With the updated global atmospheric inversion results of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) produced by the Global Carbon Project, we adjust the inversion results of all countries for comparison, considering lateral river transfer processes and trade in crop and timber products, as well as the role of carbon sequestration in unmanaged land not considered by NGHGI, and compare them with greenhouse gas budgets in national inventories. The results show that there is a good consistency in net land CO2 flux based on the global in-situ network and that using satellite CO2 retrievals over tropical countries like Congo, Brazil, Peru, South Africa, and so on. For CH4, while the uncertainties of inversion results have been reduced in the updated global inversion ensembles compared to the previous ones, it seems that oil and gas-extracting countries like Saudi Arabia and Qatar report lower emissions compared to those estimated by inversions. This study is a reapplication of the methodologies developed by our previous study, which are confirmed and could be applied regularly and show how inversion could be used systematically in the future to support the assessment and improve the inventory of the Paris Agreement.
How to cite: Deng, Z., Ciais, P., Hu, L., Saunois, M., Chevallier, F., Xiao, L., Liu, Z., and Zhou, W.: Reconciliation of updated greenhouse gas budgets from UNFCCC national inventories and atmospheric inversions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16441, https://doi.org/10.5194/egusphere-egu23-16441, 2023.
