Progress in Earth and Planetary Science最新文献

{"title":"Integration of new zircon U–Pb ages with biostratigraphy to establish a high-precision age model of the Miocene Nakayama Formation on Sado Island in Central Japan","authors":"Jumpei Yoshioka, Kenji M. Matsuzaki, Sota Niki, Junichiro Kuroda, Takafumi Hirata","doi":"10.1186/s40645-024-00651-w","DOIUrl":"https://doi.org/10.1186/s40645-024-00651-w","url":null,"abstract":"<p>The most common age constraint for the diatomaceous sediments is biostratigraphy of siliceous microfossils. Although biostratigraphy is a powerful tool to establish stratigraphy and correlate with sedimentary sequences in other sites, biostratigraphy generally includes uncertainties difficult to evaluate. In this study, we measured zircon U–Pb ages of eight tuff beds intercalated with diatomaceous mudstone of the Nakayama Formation on Sado Island in Central Japan and integrated the U–Pb ages with diatom and radiolarian biostratigraphy, whose ages and errors were re-evaluated by this study, to establish an age model precisely representing the sedimentary age. Two tuff beds in the upper and middle part of the formation offered zircon U–Pb ages of 6.7 ± 0.2 Ma and 10.87 ± 0.07 Ma, which are consistent with biostratigraphy, and provided a good example of effective integration of zircon U–Pb ages with the biostratigraphy. On the other hand, zircon U–Pb ages of the other six tuff beds in the lower part are around 12 Ma and not distinguishable from each other. In addition, older zircon grains in the 6 tuff beds are assembled in the interval from 30 to 20 Ma, which is consistent with the age of the volcanic basement rocks forming most part of Sado Island. Similarities in chemical compositions of glass shards and age distributions of zircon grains indicate that the volcaniclastic components in the tuff beds should originate from single or associated magmatic activities.</p>","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"75 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electrochemical survey of electroactive microbial populations in deep-sea hydrothermal fields","authors":"Masahiro Yamamoto, Yoshifumi Kawada, Yoshihiro Takaki, Kosuke Shimoniida, Mariko Shitara, Akiko Tanizaki, Hiroyuki Kashima, Miho Hirai, Yutaro Takaya, Tatsuo Nozaki, Takafumi Kasaya, Ken Takai","doi":"10.1186/s40645-024-00650-x","DOIUrl":"https://doi.org/10.1186/s40645-024-00650-x","url":null,"abstract":"<p>Electric discharge in deep-sea hydrothermal fields leads us to expect the existence of electroactive microbial ecosystems in the environments. Electrochemical properties such as electric field distribution on the seafloor and electrical conductivity of the rock can be useful indicators of searching electroactive microbial community in natural environments. We performed electric field measurements in deep-sea hydrothermal fields and collected rock samples by a remotely operative vehicle (ROV) operation. Several spots on the seafloor with strong electric fields were detected, which included both active hydrothermal vent areas and inactive sulfide deposits far from the vents. The electrical conductivity of the rock samples was correlated with the copper and iron sulfide content. Microbial community compositions of the rock samples were characterized by small subunit (SSU) rRNA gene amplicon sequencing analysis. The abundance of several microbial components, which are highly related to electroactive microorganisms such as <i>Geobacteraceae</i> and <i>Thiomicrorhabdus,</i> was affected by the electrical properties of rock samples. The results suggested that electrochemical properties on the seafloor would be related to the abundance of possible electroactive microbial populations, and that the electrochemical survey may be a powerful tool for exploring electroactive ecosystems.</p>\u0000","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"14 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulation of nitrogen isotopic ratios of cellular components","authors":"Naohiko Ohkouchi, Yuta Isaji, Nanako O. Ogawa","doi":"10.1186/s40645-024-00646-7","DOIUrl":"https://doi.org/10.1186/s40645-024-00646-7","url":null,"abstract":"<p>This paper is an attempt to generalize the nitrogen isotope information of the molecules that make up the cell from our point of view. Nitrogen in the cell exists as 20 proteinaceous amino acids, nucleobases, hemes, chlorophylls, and others, and their composition is similar among organisms. Based on a physiologically simple autonomous system that maintains a balance between inputs and outputs, it is theoretically predicted that ¹⁵N is distributed to each cellular compound with a certain regularity, and thus a specific relationship in nitrogen isotopic ratios among compounds. Previous studies essentially confirm this. The nitrogen isotopic ratio of compound <i>i</i> constituting the cell can be generalized as <i>δ</i>¹⁵N_<i>i</i> = <i>δ</i>¹⁵N_plant + <i>Δ</i>_i (<i>TP</i> − 1) + <i>γ</i>_<i>i</i>, where TP represents the trophic position, and <i>Δ</i>_<i>i</i> and <i>γ</i>_<i>i</i> are the trophic discrimination factor and the intracellular ¹⁵N distribution of compound <i>i</i>, respectively. Knowing reliable values of <i>Δ</i>_<i>i</i> and <i>γ</i>_<i>i</i> will help us to better understand nitrogen dynamics in the biosphere and advance our understanding of the picture of the Earth’s environment through biogeochemistry.</p>","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"39 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Basal emission rates of isoprene and monoterpenes from major tree species in Japan: interspecies and intraspecies variabilities","authors":"Akira Tani, Noboru Masui, Ting-Wei Chang, Motonori Okumura, Yutaka Kokubu","doi":"10.1186/s40645-024-00645-8","DOIUrl":"https://doi.org/10.1186/s40645-024-00645-8","url":null,"abstract":"<p>Uncontrolled terpenoid emissions from forest trees in Japan may have contributed to high O₃ concentrations observed in urban and suburban areas. To estimate ozone formation via a series of reactions between NO_<i>x</i> and terpenoids using atmospheric chemistry models, it is important to produce terpenoid emission inventories by collecting all reported emission data for the major tree species in Japan and examining their reliability. In this review, we first describe three different plant terpenoid emission types, i.e., isoprene-emitting type, monoterpene-emitting type with storage tissues and organs, and monoterpene-emitting type without storage tissues and organs. Second, we describe various methods for measuring plant terpenoid emissions, including a recently developed simplified method, and explain their reliability. We emphasized that applicable measurement methods depend on the terpenoid emission types. Data obtained using static chamber methods should not be considered because they have the highest uncertainty resulting from normal chamber materials that are not specific to terpenoid measurements and lack humidity control. Finally, we show the absolute values of the collected emission rates and describe their variability. The deciduous oak species, <i>Quercus serrata</i> and <i>Quercus mongolica</i> var. <i>crispula</i>, and bamboo species, <i>Phyllostachys pubescens</i> and <i>Phyllostachys bambusoides,</i> are strong isoprene emitters. Among the monoterpene emitters, four evergreen broadleaf trees, including three <i>Quercus</i> species, had the highest basal emission rate (BER). The monoterpene storage type conifers <i>Larix kaempferi</i> and <i>Pinus densiflora</i> have relatively lower BERs. Emission data are not available for <i>Castanopsis cuspidata</i>, and seasonal changes in emission rates have not been reported for several major tree species in the top 20 rankings. Within species, the reported emission rates of some tree species differed by threefold. These differences may be attributed to the reliability of the measurement and analytical systems, tree age, leaf morphology, environmental conditions, and genetic diversity. We emphasize the need for reliable measurements to achieve a more precise terpenoid emission inventory for major tree species in Japan.</p>\u0000","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"15 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141870289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the relative activity of faulting along both flanks of the Ou Backbone Range, Tohoku Region, Japan, from fluvial geomorphic analyses","authors":"J. Bruce H. Shyu, Jhih-Hao Liao, Chia-Yu Chen, Hiroyuki Tsutsumi, Yasufumi Iryu","doi":"10.1186/s40645-024-00644-9","DOIUrl":"https://doi.org/10.1186/s40645-024-00644-9","url":null,"abstract":"<p>The Ou Backbone Range in the Tohoku Region of Japan is bounded on its both sides by two major active fault systems: the Western Fault Zone of Kitakami Lowland in the east and the Eastern Fault Zone of Yokote Basin in the west. Although these two systems are primary active fault systems in the region, information on their long-term activity characteristics is still quite limited. Therefore, we analyzed the normalized channel steepness indexes of river valleys trending perpendicular to the range front along both flanks of the Ou Backbone Range. Our results show that the eastern flank has gentler river valleys, whereas rivers along the northwestern flank are steeper. Our field investigation shows that knickpoints in this area are mostly related to local lithologic boundaries or are check dams along the valleys, thus the river systems are likely under steady-state conditions. Hence, the steeper river valleys in northwestern Ou Backbone Range indicate a higher uplift rate of the area. Because both fault systems are primarily dip-slip reverse faults and do not have significant variations in their subsurface geometry, the faster uplift suggests that the northern segment of the Eastern Fault Zone of Yokote Basin has a higher slip rate. This is consistent with results of previous studies, and the fact that the rupture of the 1896 Rikuu earthquake, the only historical surface-rupturing event in this region, was only limited along the northern segment of this fault system.</p>","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"13 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141567466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Imaging flow focusing and isolation of aqueous fluids in synthetic quartzite: implications for permeability and retained fluid fraction in deep-seated rocks","authors":"Wakana Fujita, Michihiko Nakamura, Kentaro Uesugi, Philipp Eichheimer, Marcel Thielmann, Gregor J. Golabek","doi":"10.1186/s40645-024-00632-z","DOIUrl":"https://doi.org/10.1186/s40645-024-00632-z","url":null,"abstract":"<p>The microstructure of realistic fluid–rock systems evolves to minimize the overall interfacial energy, enabling local variations in fluid geometry beyond ideal models. Consequently, the permeability–porosity relationship and fluid distribution in these systems may deviate from theoretical expectations. Here, we aimed to better understand the permeability development and fluid retention in deep-seated rocks at low fluid fractions by using a combined approach of high-resolution synchrotron radiation X-ray computed microtomography imaging of synthesized rocks and numerical permeability computation. We first synthesized quartzite using a piston-cylinder apparatus at different fluid fractions and wetting properties (wetting and non-wetting systems with dihedral angles of 52° and 61°–71°, respectively) under conditions of efficient grain growth. Although all fluids should be connected along grain edges and tubules in the homogeneous isotropic wetting fluid–rock system enabling segregation by gravitational compaction in natural settings, the fluid connectivity rapidly decreased to ~ 0 when the total fluid fraction decreased to 0.030–0.037, as the non-ideality of quartzite, including the interfacial energy anisotropy (i.e., grain faceting), became critical. In non-wetting systems, where the minimum energy fluid fraction based solely on the dihedral angle is ~ 0.015–0.035, the isolated (disconnected) fractions was 0.048–0.062. A streamline computation in the non-wetting system revealed that with decreasing total porosity, flow focusing into fewer channels maintained permeability, allowing the effective segregation of the connected fluids. These results provide insight into how non-wetting fluids segregate from rocks and exemplify the fraction of retained fluids in non-wetting systems. Thus, the findings suggest a potential way for wetting system fluids to be transported into the deep Earth's interior, and the amount of fluids dragged down to the Earth’s interior could be higher than what was previously estimated.</p>\u0000","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"13 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141567682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal thickness variations beneath Egypt through gravity inversion and forward modeling: linking surface thermal anomalies and Moho topography","authors":"Ahmed Mohamed Bekhit, Mohamed Sobh, Mohamed Abdel Zaher, Tharwat Abdel Fattah, Ahmed I. Diab","doi":"10.1186/s40645-024-00639-6","DOIUrl":"https://doi.org/10.1186/s40645-024-00639-6","url":null,"abstract":"<p>This study aims to quantify the topography of the Moho boundary, the lower crust and uppermost mantle contact of Egypt, in order to estimate the crustal thickness variation and its link to the distribution of thermal anomalies under Egypt. This is accomplished by modeling satellite gravity, supported by the passive seismic constraints throughout Egypt. However, when estimating the thickness of the crust in Egypt using just seismic data, substantial uncertainty and deviation are produced due to the sparsely dispersed stations. Integrating seismic and gravity data minimizes uncertainty and improves estimate accuracy. The investigation is broken down into four stages, the first involving utilizing the Sentinel-3B satellite to create land surface temperature maps. The subsequent steps consist of gravity and seismic data adjustments, inversion and forward modeling. We used seismically restricted nonlinear inversion to look at Goco06s satellite gravity data to model the Moho’s topographic surface. The data gathered from deep seismic refraction and receiver functions adjusted the analyzed data. The inversion process relies on the adapted Bott's approach and Tikhonov regularization, using the assumption of the sphericity of the Earth planet. Reference values for depth of Moho and density contrast were set at 35 km and 500 kg/m³, respectively. The average statistical difference for Moho depth between gravity-based model and seismic data is − 0.10 km. Through forward gravity modeling, five gravity profiles were chosen and interpreted in 2.5D models. The results indicated that the Moho depth in the south varies from 35 to 39 km and decreases in the north and the Mediterranean. In upper Egypt, the highest Moho depth is 39 km. The depth varies beneath the Sinai Peninsula as it is about 35 km in its south, reaches 30 km in the northern portion, and ranges along the Red Sea’s Rift Margin from 29 to 32 km. Moreover, the final model shows the relation between Moho coincides with the surface temperature anomalies approved by satellite images and hot springs. The model reveals a correlation between Moho discontinuity and surface temperature anomalies, revealing the highest geothermal potential in a rectangular area in central Egypt, between latitudes 25°N and 30°N, based on satellite imagery and hot springs distribution.</p>\u0000","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"25 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141567681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence for suboceanic small-scale convection from a “garnet”-bearing lherzolite xenolith from Aitutaki Island, Cook Islands","authors":"Norikatsu Akizawa, Kazuhito Ozawa, Tetsu Kogiso, Akira Ishikawa, Akira Miyake, Yohei Igami, Simon R. Wallis, Takayoshi Nagaya, Chihiro Ohshima, Ryo Fujita, Tatsuhiko Kawamoto, Akihiro Tamura, Tomoaki Morishita, Shoji Arai, Atsushi Yasumoto","doi":"10.1186/s40645-024-00643-w","DOIUrl":"https://doi.org/10.1186/s40645-024-00643-w","url":null,"abstract":"<p>Garnet peridotite xenoliths have been rarely reported from suboceanic mantle. Petrographic and geochemical characteristics of garnet-bearing oceanic peridotite xenoliths provide precious information on dynamics of the suboceanic lithosphere and asthenosphere interaction. We examined a lherzolite xenolith included in olivine nephelinite lava from Aitutaki Island, a member of the Cook-Austral volcanic chain. The lherzolite xenolith contains reddish fine-grained (&lt; 5 µm in size) mineral aggregates (FMAs) with size range of 0.5–6 mm, consisting of olivine, calcic and sodic plagioclases, aluminous spinel, native iron, and nepheline. Microstructural observations and chemical data corroborate that the FMA is a decomposed pyrope-rich garnet including chromian spinel grains with an irregular highly indented morphology in the center. The FMA is surrounded by pyroxene-poor and olivine-rich aureole. The spatial and morphological relationships of FMA and chromian spinel with pyroxene-depleted margin suggest a reaction of aluminous spinel + pyroxenes → pyrope-rich garnet + olivine, which requires a compression before decomposition of the garnet to FMA. An orthopyroxene grain shows slight but clear chemical zoning characterized by increase in Al, Ca, and Cr from the grain center to the rim. The zoning patterns of Al and Ca in the orthopyroxene grain can be modeled by diffusion-controlled solid-state reactions induced by pressure and temperature changes, keeping surface concentrations in equilibrium with the other coexisting mineral phases. The results indicate that the mantle, from which the lherzolite xenolith was derived, underwent isothermal decompression followed by a weak heating on a time scale of a few tenths of million years before the xenolith extraction. From the deduced compression and decompression histories, we hypothesize that the mantle beneath Aitutaki Island was once dragged down to a garnet-stable deep mantle region and brought up later by small-scale sublithospheric convection.</p>\u0000","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"37 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chasing parts in quadrillion: applications of dynamical downscaling in atmospheric pollutant transport modelling during field campaigns","authors":"Alexandros Panagiotis Poulidis, Sarah-Lena Seemann, Hans Schlager, Mihalis Vrekoussis","doi":"10.1186/s40645-024-00642-x","DOIUrl":"https://doi.org/10.1186/s40645-024-00642-x","url":null,"abstract":"<p>Atmospheric transport and dispersion models (ATDMs) are widely used to study and forecast pollution events. In the frame of the “Effect of Megacities on the transport and transformation of pollutants on the regional to global scales” (EMeRGe) project, ATDM forecasts were carried out to identify potential airborne sampling areas of perfluorocarbons (PFCs) emanating from controlled PFC releases. The forecasts involved short-distance transport over small-scale topographic maxima (Manilla; Philippines), short-distance transport over large-scale topographic maxima (Taipei, Taiwan) and long-distance transport over mixed topography (Nanjing, China, sampled over Taiwan). In situ aircraft measurements of PFC mixing ratios down to a few parts per quadrillion (ppqv) provide us with a unique dataset to explore the added benefits of dynamical downscaling. Transport simulations were repeated using FLEXPART driven by ERA5 and IFS meteorological data and FLEXPART-WRF with dynamically downscaled IFS data down to 1.1 km and four PBL parametrisations. Of the three cases studied, dynamical downscaling led to significant differences for the Manilla and Taipei releases that can be interpreted through changes in the modelled orographic flow regimes. The choice of PBL scheme also significantly impacted accuracy, but there was no systematically better-performing option, highlighting the benefits of ensemble forecasting. Results show how convergence and divergence between ensemble members can be utilised to help decision-making during field campaigns. This study highlights the role that dynamical downscaling can play as an important component in campaign planning when dealing with observations over orographically complex areas.</p>","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"27 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141522814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the impact of observations at Nainital (India) and Comilla (Bangladesh) on the CH4 flux inversion","authors":"Dmitry A. Belikov, Prabir K. Patra, Yukio Terao, Manish Naja, Md. Kawser Ahmed, Naoko Saitoh","doi":"10.1186/s40645-024-00634-x","DOIUrl":"https://doi.org/10.1186/s40645-024-00634-x","url":null,"abstract":"<p>Methane emission in South Asia is poorly understood due to a lack of observations, despite being a major contributor to methane emissions globally. We present the first results of atmospheric CH₄ inversions using air samples collected weekly at Nainital, India (NTL), and Comilla, Bangladesh (CLA), in addition to surface background flask measurements by NOAA, CSIRO and AGAGE using the MIROC4-ACTM. Our simulations span from 2000 to 2020 (considering the fixed “edge” effect), but the main analysis period is 2013–2020, when both the NTL and CLA datasets are available. An additional flux uncertainty reduction of up to 40% was obtained (mainly in the northern part of the Indian subcontinent), which enhanced our confidence in flux estimation and reaffirmed the significance of observations at the NTL and CLA sites. Our estimated regional flux was 64.0 ± 4.7 Tg-CH₄ yr⁻¹ in South Asia for the period 2013–2020. We considered two combinations of a priori fluxes that represented different approaches for CH₄ emission from rice fields and wetlands. By the inversion, the difference in emissions between these combinations was notably reduced due to the adjustment of the CH₄ emission from the agriculture, oil and gas, and waste sectors. At the same time, the discrepancy in wetland emissions, approximately 8 Tg-CH₄ yr⁻¹, remained unchanged. In addition to adjusting the annual totals, the inclusion of NTL/CLA observations in the inversion analysis modified the seasonal cycle of total fluxes, possibly due to the agricultural sector. While the a priori fluxes consisted of a single peak in August, the a posteriori values indicated double peaks in May and September. These peaks are highly likely associated with field preparation for summer crops and emissions from rice fields during the heading stage (panicle formation). The newly incorporated sites primarily exhibit sensitivity to the Indo-Gangetic Plain subregion, while coverage in southern India remains limited. Expanding the observation network is necessary, with careful analysis of potential locations using back-trajectory methods for footprint evaluation.</p>","PeriodicalId":54272,"journal":{"name":"Progress in Earth and Planetary Science","volume":"10 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}