Global Biogeochemical Cycles最新文献

{"title":"Dissolved Nitrogen Cycling in the Eastern Canadian Arctic Archipelago and Baffin Bay From Stable Isotopic Data","authors":"H. C. Westbrook,&nbsp;A. Bourbonnais,&nbsp;C. C. M. Manning,&nbsp;J.-É. Tremblay,&nbsp;M. M. M. Ahmed,&nbsp;B. Else,&nbsp;J. Granger","doi":"10.1029/2023GB007926","DOIUrl":"10.1029/2023GB007926","url":null,"abstract":"<p>Climate change is expected to alter the input of nitrogen (N) sources in the Eastern Canadian Arctic Archipelago and Baffin Bay due to increased discharge from glacial meltwater and permafrost thaw. Since dissolved inorganic N is generally depleted in surface waters, dissolved organic N (DON) could represent a significant N source fueling phytoplankton activity in Arctic ecosystems. Yet, few DON data for this region exist. We measured concentrations and stable isotope ratios of DON (δ¹⁵N) and nitrate (NO₃⁻; δ¹⁵N and δ¹⁸O) to investigate the sources and cycling of dissolved nitrogen in regional rivers and marine samples collected in the Eastern Canadian Arctic Archipelago and Baffin Bay during the summer of 2019. The isotopic signatures of NO₃⁻ in rivers could be reproduced in a steady state isotopic model by invoking mixing between atmospheric NO₃⁻ and nitrified ammonium as well as NO₃⁻ assimilation by phytoplankton. DON concentrations were low in most rivers (≤4.9 μmol N L⁻¹), whereas the concentrations (0.54–12 μmol N L⁻¹) and δ¹⁵N of DON (−0.71–9.6‰) at the sea surface were variable among stations, suggesting dynamic cycling and/or distinctive sources. In two regions with high chlorophyll-a, DON concentrations were inversely correlated with chlorophyll-a and the δ¹⁵N of DON, suggesting net DON consumption in localized phytoplankton blooms. We derived an isotope effect of 6.9‰ for DON consumption. Our data helps establish a baseline to assess future changes in the nutrient regime for this climate-sensitive region.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 12","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11650013/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142853583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"System-Wide Greenhouse Gas Emissions From Mountain Reservoirs Draining Permafrost Catchments on the Qinghai-Tibet Plateau","authors":"Liwei Zhang,&nbsp;Emily H. Stanley,&nbsp;Gerard Rocher-Ros,&nbsp;Joshua F. Dean,&nbsp;Dongfeng Li,&nbsp;Qingrui Wang,&nbsp;Ling Zhang,&nbsp;Wenqing Shi,&nbsp;Tian Xie,&nbsp;Xinghui Xia","doi":"10.1029/2024GB008112","DOIUrl":"https://doi.org/10.1029/2024GB008112","url":null,"abstract":"<p>Reservoirs influence the global climate by exchanging greenhouse gases (GHGs) of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) with the atmosphere. Few studies, however, quantify emissions of all three GHGs from reservoirs, particularly in permafrost-affected mountain regions where ecosystems are highly vulnerable to climate change. This study presents three-year direct measurements of CO₂, CH₄, and N₂O concentrations and fluxes upstream, within, and downstream from two reservoirs draining permafrost catchments on the Qinghai-Tibet Plateau, including periods of reservoir drawdown. Comparing GHG fluxes across space and time exhibits a general pattern of lower fluxes at the two reservoirs relative to up- and downstream channels. Ebullitive fluxes contributed to 36.7% and 9.4% of total CH₄ and N₂O fluxes, respectively. CO₂ has no response to drawdown, but CH₄ and N₂O display synchronous drawdown-associated increase within the reservoir, constituting 57.5% and 32.8% of the annual reservoir emissions in just 2 months, respectively. Riverine emissions from up- and downstream channels accounted for an outsized fraction (55.5% for CH₄, 17.3% for CO₂ and 16.5% for N₂O) of the system-wide GHG budget. Compared with global reservoirs, the two reservoirs have high CO₂ and N₂O but low CH₄ fluxes in CO₂ equivalents. Upscaling shows that the two reservoirs emit the same magnitude of carbon as thermokarst lakes, and four times higher N₂O than Finnish lakes on an areal basis. This article shows that alpine reservoirs draining permafrost catchments are unrecognized atmospheric sources in current reservoir GHG inventories, but also emphasizes the importance of system-wide emissions when assessing total GHG evasion from reservoir systems.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 12","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142861235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interactions Between Multiple Physical Particle Injection Pumps in the Southern Ocean","authors":"Andrew F. Thompson,&nbsp;Lilian A. Dove,&nbsp;Ellie Flint,&nbsp;Leo Lacour,&nbsp;Philip Boyd","doi":"10.1029/2024GB008122","DOIUrl":"https://doi.org/10.1029/2024GB008122","url":null,"abstract":"&lt;p&gt;Contributions to the biological pump that arise from the physical circulation are referred to as physical particle injection pumps. A synthesized view of how these physical pumps interact with each other and other components of the biological pump does not yet exist. Here, observations from a quasi-Lagrangian float and an ocean glider, deployed in the Southern Ocean's Subantarctic Zone for one month during the spring bloom, offer insight into daily-to-monthly fluctuations in the mixed layer pump (MLP) and the eddy subduction pump (ESP). Estimated independently, each mechanism contributes intermittent export fluxes of roughly several hundred milligrams of particulate organic carbon (POC) per square meter per day. The glider-based estimates indicate sustained weekly periods of MLP export fluxes across the base of the mixed layer with a magnitude of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;mn&gt;450&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;110&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} 450pm 110$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; mg POC &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}}^{-2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mtext&gt;day&lt;/mtext&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{day}}^{-1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. Potential export fluxes from the ESP, based on a mixed layer instability scaling, occasionally exceed 400 mg POC &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}}^{-2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mtext&gt;day&lt;/mtext&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{day}}^{-1}$&lt;/annotation&gt;\u0000 ","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 12","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008122","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial Variability of Dissolved Cobalt in the Indian Ocean Waters: Contrasting Behavior in the Arabian Sea, the Bay of Bengal and the Southern Sector of the Indian Ocean","authors":"Nirmalya Malla,&nbsp;Sunil Kumar Singh","doi":"10.1029/2024GB008291","DOIUrl":"https://doi.org/10.1029/2024GB008291","url":null,"abstract":"<p>The present study explored the dynamics of total dissolved Cobalt (dCo) in the Indian Ocean, revealing different distribution patterns in the different sub-basins, nutrient-type in the southern sector, hybrid-type in the Arabian Sea to scavenged-type in the Bay of Bengal (BoB). The dCo in the coastal water of the Arabian Sea displays elevated (0.12–0.13 nmol L⁻¹) abundance and diminishes gradually toward the central Arabian Sea. Similarly, in the BoB, dCo concentrations are notably higher in the northern region (0.11 nmol L⁻¹) and gradually decrease toward the south (0.03 nmol L⁻¹ at 5°N). The Arabian Sea with higher biological uptake and remineralization in the oxycline supports a higher abundance of dCo in the intermediate oxygen minimum zone (OMZ), much a like the OMZs of the Atlantic and the Pacific Oceans. The influence of the phytoplankton community shift and uptake on the dCo distribution in the Indian Ocean could be inferred from the association between Co and phosphate in the photic waters. Our observation demonstrates a scavenging type dCo profile in the BoB due to its higher riverine as well as dust inputs in addition to its supply from continental shelf sediments. Such a higher concentration of dCo in the surface waters of the northern BoB masks the dCo signal associated with nitrite maxima. dCo gets removed by its scavenging with Mn oxides at deeper depths, as reflected by higher particulate Co in the BoB. Subduction fluids contribute significantly to the dCo inventory of the deep water in the Indian Ocean near the Java-Sumatra subduction zone.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 12","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142764295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic Coatings Reduce Dissolution Rate by an Order of Magnitude for Carbonate Minerals Produced by Marine Fish","authors":"Amanda M. Oehlert,&nbsp;Sarah Walls,&nbsp;Katelyn Arista,&nbsp;Jazmin Garza,&nbsp;Erik J. Folkerts,&nbsp;Brooke E. Vitek,&nbsp;Sadegh Tale Masoule,&nbsp;Clément G. L. Pollier,&nbsp;Gaëlle Duchâtellier,&nbsp;John D. Stieglitz,&nbsp;Daniel D. Benetti,&nbsp;Rachael M. Heuer,&nbsp;Ali Ghahremaninezhad,&nbsp;Martin Grosell","doi":"10.1029/2024GB008176","DOIUrl":"https://doi.org/10.1029/2024GB008176","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Marine carbonate production and dissolution are important components of the global carbon cycle and the marine alkalinity budget. Global carbonate production by marine fish (ichthyocarbonate) has been estimated to be as high as 9.03 Pg CaCO₃ yr⁻¹; however, the fate of ichthyocarbonate is poorly understood. High magnesium concentrations in ichthyocarbonate would traditionally suggest rapid dissolution under current marine conditions, but a correlation between dissolution rate and mol%MgCO₃ has not been observed. Here, we aim to determine the role of organic coatings on dissolution rates of ichthyocarbonate in marine environments. We applied a combination of petrographic, geochemical, and microCT approaches to assess the quantity and distribution of organic matter in ichthyocarbonate produced by two species of marine fish, the Gulf toadfish (<i>Opsanus beta</i>) and the Olive flounder (<i>Paralichthys olivaceus</i>). We show that organic matter, including external coatings and embedded organic material, is volumetrically significant, ranging from 8.5% to 32.3% of ichthyocarbonate by volume. Bleach oxidation of external organic matter coatings increased the dissolution rate of ichthyocarbonate by more than an order of magnitude, suggesting these coatings serve to reduce reactive surface area of the mineral fraction in ichthyocarbonate. Assuming that organic coatings do not influence sinking rates, external coatings extend the depth of ichthyocarbonate persistence in the water column by ∼12–15×. Therefore, organic coatings are an important determinant of the role of ichthyocarbonate in the marine carbon cycle.</p>\u0000 </section>\u0000 </div>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 11","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008176","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"210Po and 210Pb Distributions Along the GEOTRACES Pacific Meridional Transect (GP15): Tracers of Scavenging and Particulate Organic Carbon (POC) Export","authors":"J. Kirk Cochran,&nbsp;Ziran Wei,&nbsp;Evan Horowitz,&nbsp;Patrick Fitzgerald,&nbsp;Christina Heilbrun,&nbsp;Mark Stephens,&nbsp;Phoebe J. Lam,&nbsp;Emilie Le Roy,&nbsp;Matthew Charette","doi":"10.1029/2024GB008243","DOIUrl":"https://doi.org/10.1029/2024GB008243","url":null,"abstract":"<p>Distributions of the natural radionuclide ²¹⁰Po and its grandparent ²¹⁰Pb along the GP15 Pacific Meridional Transect provide information on scavenging rates of reactive chemical species throughout the water column and fluxes of particulate organic carbon (POC) from the primary production zone (PPZ). ²¹⁰Pb is in excess of its grandparent ²²⁶Ra in the upper 400–700 m due to the atmospheric flux of ²¹⁰Pb. Mid-water ²¹⁰Pb/²²⁶Ra activity ratios are close to radioactive equilibrium (1.0) north of ∼20°N, indicating slow scavenging, but deficiencies at stations near and south of the equator suggest more rapid scavenging associated with a “particle veil” located at the equator and hydrothermal processes at the East Pacific Rise. Scavenging of ²¹⁰Pb and ²¹⁰Po is evident in the bottom 500–1,000 m at most stations due to enhanced removal in the nepheloid layer. Deficits in the PPZ of ²¹⁰Po (relative to ²¹⁰Pb) and ²¹⁰Pb (relative to ²²⁶Ra decay and the ²¹⁰Pb atmospheric flux), together with POC concentrations and particulate ²¹⁰Po and ²¹⁰Pb activities, are used to calculate export fluxes of POC from the PPZ. ²¹⁰Po-derived POC fluxes on large (&gt;51 μm) particles range from 15.5 ± 1.3 mmol C/m²/d to 1.5 ± 0.2 mmol C/m²/d and are highest in the Subarctic North Pacific; ²¹⁰Pb-derived fluxes range from 6.7 ± 1.8 mmol C/m²/d to 0.2 ± 0.1 mmol C/m²/d. Both ²¹⁰Po- and ²¹⁰Pb-derived POC fluxes are greater than those calculated using the ²³⁴Th proxy, possibly due to different integration times of the radionuclides, considering their different radioactive mean-lives and scavenging mean residence times.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 11","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extreme Climate as the Primary Control of Global Soil Organic Carbon Across Spatial Scales","authors":"Yucheng Wei,&nbsp;Mingming Wang,&nbsp;R. A. Viscarra Rossel,&nbsp;Hong Chen,&nbsp;Zhongkui Luo","doi":"10.1029/2024GB008200","DOIUrl":"https://doi.org/10.1029/2024GB008200","url":null,"abstract":"<p>Soil organic carbon (SOC) stock exhibits substantial variability across spatial scales and depths. Drivers of such variability may be scale- and depth-dependent, but have been rarely systematically investigated. Assessing SOC measurements of 113,013 soil profiles worldwide, we show that climate, encompassing mean modern- and paleo-climate and climate extremes, is the predominant determinant across scales (from 50 km to the globe) and depths, explaining 34%–62% of the spatial variability of SOC stocks depending on the spatial scale and soil depth layer assessed. On finer scales (50–100 km), soil properties and mean modern- and paleo-climate are dominant in all soil depth layers. At broader scales (&gt;100 km), the significance of climate extremes intensifies, alone explaining 27%–32% of the spatial variability of SOC stocks. Furthermore, we find nonlinear relationships of SOC stocks with most factors, while the relationship with the same factor is distinct across scales and depths. These results reinforce climate, particularly extremes, as the primary driving force of whole-soil carbon distribution across the globe, emphasizing the need to factor extremes into carbon management strategies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 11","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Comprehensive Analysis of Air-Sea CO2 Flux Uncertainties Constructed From Surface Ocean Data Products","authors":"Daniel J. Ford,&nbsp;Josh Blannin,&nbsp;Jennifer Watts,&nbsp;Andrew J. Watson,&nbsp;Peter Landschützer,&nbsp;Annika Jersild,&nbsp;Jamie D. Shutler","doi":"10.1029/2024GB008188","DOIUrl":"https://doi.org/10.1029/2024GB008188","url":null,"abstract":"<p>Increasing anthropogenic CO₂ emissions to the atmosphere are partially sequestered into the global oceans through the air-sea exchange of CO₂ and its subsequent movement to depth, commonly referred to as the global ocean carbon sink. Quantifying this ocean carbon sink provides a key component for closing the global carbon budget, which is used to inform and guide policy decisions. These estimates are typically accompanied by an uncertainty budget built by selecting what are perceived as critical uncertainty components based on selective experimentation. However, there is a growing realization that these budgets are incomplete and may be underestimated, which limits their power as a constraint within global budgets. In this study, we present a methodology for quantifying spatially and temporally varying uncertainties in the air-sea CO₂ flux calculations for the <i>f</i>CO₂-product based assessments that allows an exhaustive assessment of all known sources of uncertainties, including decorrelation length scales between gridded measurements, and the approach follows standard uncertainty propagation methodologies. The resulting standard uncertainties are higher than previously suggested budgets, but the component contributions are largely consistent with previous work. The uncertainties presented in this study identify how the significance and importance of key components change in space and time. For an exemplar method (the UExP-FNN-U method), the work identifies that we can currently estimate the annual ocean carbon sink to a precision of ±0.70 Pg C yr⁻¹ (1σ uncertainty). Because this method has been built on established uncertainty propagation and approaches, it appears that applicable to all <i>f</i>CO₂-product assessments of the ocean carbon sink.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 11","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008188","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Setting Up Methane Mitigation Measures for Indian Rice Fields: Representative Emissions and New Interpretations","authors":"Fida Mohammad Sahil,&nbsp;Mukund Narayanan,&nbsp;Idhayachandhiran Ilampooranan","doi":"10.1029/2024GB008107","DOIUrl":"https://doi.org/10.1029/2024GB008107","url":null,"abstract":"<p>Rice cultivation produces methane (CH₄) due to anaerobic conditions induced by flood irrigation, significantly contributing to global warming. While most studies use national emission factors (EFs), our study synthesized 726 published measurements across India (the second largest methane emitter after China) to develop district-level water regime-specific EFs for estimating district-scale emissions and warming potential. CH₄ emissions from Indian rice fields increased from 3.7 (3.4–4.1) Tg to 4.8 (4.4–5.3) Tg during 1966–2017, driven by rice area and water-regime variations. Meanwhile, district-level emissions increased by ∼930%, influenced by management practices such as animal manure, fertilizer application, and water input, accurately reflecting regional variations compared to previous estimates. Employing a novel muti-output random forest mitigation model (<i>R</i>² ∼ 0.9), we found that a 25% warming reduction at the district-level requires curtailing animal manure, nitrogen fertilizer, and water input by 8.5%, 12.9%, and 10.9%, respectively. These curtailments nearly double for a 50% mitigation scenario. Comparing our emissions with previous bottom-up studies (used as inputs in global climate models) revealed discrepancies in prior national figures. With top-down estimates, our emissions correlated positively, suggesting higher reliability. Including our new regionally validated data in global climate models may provide more accurate climate projections at the Indian and global scales.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 11","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142541099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Permafrost Region Greenhouse Gas Budgets Suggest a Weak CO2 Sink and CH4 and N2O Sources, But Magnitudes Differ Between Top-Down and Bottom-Up Methods","authors":"G. Hugelius,&nbsp;J. Ramage,&nbsp;E. Burke,&nbsp;A. Chatterjee,&nbsp;T. L. Smallman,&nbsp;T. Aalto,&nbsp;A. Bastos,&nbsp;C. Biasi,&nbsp;J. G. Canadell,&nbsp;N. Chandra,&nbsp;F. Chevallier,&nbsp;P. Ciais,&nbsp;J. Chang,&nbsp;L. Feng,&nbsp;M. W. Jones,&nbsp;T. Kleinen,&nbsp;M. Kuhn,&nbsp;R. Lauerwald,&nbsp;J. Liu,&nbsp;E. López-Blanco,&nbsp;I. T. Luijkx,&nbsp;M. E. Marushchak,&nbsp;S. M. Natali,&nbsp;Y. Niwa,&nbsp;D. Olefeldt,&nbsp;P. I. Palmer,&nbsp;P. K. Patra,&nbsp;W. Peters,&nbsp;S. Potter,&nbsp;B. Poulter,&nbsp;B. M. Rogers,&nbsp;W. J. Riley,&nbsp;M. Saunois,&nbsp;E. A. G. Schuur,&nbsp;R. L. Thompson,&nbsp;C. Treat,&nbsp;A. Tsuruta,&nbsp;M. R. Turetsky,&nbsp;A.-M. Virkkala,&nbsp;C. Voigt,&nbsp;J. Watts,&nbsp;Q. Zhu,&nbsp;B. Zheng","doi":"10.1029/2023GB007969","DOIUrl":"https://doi.org/10.1029/2023GB007969","url":null,"abstract":"<p>Large stocks of soil carbon (C) and nitrogen (N) in northern permafrost soils are vulnerable to remobilization under climate change. However, there are large uncertainties in present-day greenhouse gas (GHG) budgets. We compare bottom-up (data-driven upscaling and process-based models) and top-down (atmospheric inversion models) budgets of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) as well as lateral fluxes of C and N across the region over 2000–2020. Bottom-up approaches estimate higher land-to-atmosphere fluxes for all GHGs. Both bottom-up and top-down approaches show a sink of CO₂ in natural ecosystems (bottom-up: −29 (−709, 455), top-down: −587 (−862, −312) Tg CO₂-C yr⁻¹) and sources of CH₄ (bottom-up: 38 (22, 53), top-down: 15 (11, 18) Tg CH₄-C yr⁻¹) and N₂O (bottom-up: 0.7 (0.1, 1.3), top-down: 0.09 (−0.19, 0.37) Tg N₂O-N yr⁻¹). The combined global warming potential of all three gases (GWP-100) cannot be distinguished from neutral. Over shorter timescales (GWP-20), the region is a net GHG source because CH₄ dominates the total forcing. The net CO₂ sink in Boreal forests and wetlands is largely offset by fires and inland water CO₂ emissions as well as CH₄ emissions from wetlands and inland waters, with a smaller contribution from N₂O emissions. Priorities for future research include the representation of inland waters in process-based models and the compilation of process-model ensembles for CH₄ and N₂O. Discrepancies between bottom-up and top-down methods call for analyses of how prior flux ensembles impact inversion budgets, more and well-distributed in situ GHG measurements and improved resolution in upscaling techniques.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 10","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007969","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142525538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}