Global Biogeochemical Cycles最新文献

{"title":"Climate and Vegetation-Driven Increase of Soil Heterotrophic and Autotrophic Respiration in China's Subtropical Forests Over 2000–2020","authors":"Yibo Yan,&nbsp;Wohlfahrt Georg,&nbsp;Ni Huang,&nbsp;Mengmeng Cao,&nbsp;Xiujun Wang","doi":"10.1029/2024GB008363","DOIUrl":"https://doi.org/10.1029/2024GB008363","url":null,"abstract":"<p>Soil respiration significantly counteracts the carbon sequestration of forest ecosystems, but large uncertainties remain in quantifying its components including heterotrophic (HR) and autotrophic respiration (AR). We used previously collected field data from subtropical forests of southern China, and developed independent models for HR and AR. The HR model incorporated the regulation of substrate quantity and quality and co-limitations of soil temperature and moisture on microbe activity. The AR model considered fine root biomass and productivity as substrates and temperature effects on root activity. Using high-quality forcing data and new models, we estimated HR and AR in this region over 2000–2020 with 8-day timescale and 1 km spatial resolution. Validation with independent data showed improved accuracy compared with previous estimates. We estimated annual HR at 523 ± 381 g C m⁻² yr⁻¹ and AR at 254 ± 112 g C m⁻² yr⁻¹ (values represent mean ± SD). While previous HR estimates align well with our results, previous AR estimates are generally higher. Our estimates exhibited more detailed spatial patterns than existing data sets, particularly along altitudinal gradients, and showed significant increasing trends in both HR and AR driven by warming and greening, especially in high-rate region and during summer season. Soil temperature was the main driver for the interannual variation of HR especially in cold environments, while leaf area index mainly contributed to that of AR in most regions. Our results provide critical constraints on the estimates of HR and AR in subtropical forests and enhance our understanding of their contributions and spatiotemporal patterns under a changing climate.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770100","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":"Insect Herbivory Releases More Nutrients in Warmer and Drier Forests","authors":"Bernice C. Hwang,&nbsp;Christian P. Giardina,&nbsp;M. Noelia Barrios-Garcia,&nbsp;Haoyu Diao,&nbsp;Virginia Gisela Duboscq-Carra,&nbsp;Andreas Hemp,&nbsp;Claudia Hemp,&nbsp;Mylthon Jiménez-Castillo,&nbsp;Paulina Lobos-Catalán,&nbsp;Levan Mumladze,&nbsp;Ana C. Palma,&nbsp;Ion Catalin Petritan,&nbsp;Mariano A. Rodriguez-Cabal,&nbsp;Tommi Andersson,&nbsp;Kainana S. Francisco,&nbsp;Shelley A. Gage,&nbsp;Giorgi Iankoshvili,&nbsp;Seana K. Walsh,&nbsp;Daniel B. Metcalfe","doi":"10.1029/2024GB008367","DOIUrl":"https://doi.org/10.1029/2024GB008367","url":null,"abstract":"<p>Climate, forest successional stage, and soil substrate age can alter herbivore communities and their effects on biogeochemical cycling, but the size and spatial variability of these effects are poorly quantified. To address this knowledge gap, we established a globally distributed network of 50 broadleaved old-growth forests across six continents, encompassing well-constrained local-scale gradients in mean annual temperature (MAT), mean annual precipitation (MAP), succession, and soil substrate age. We used this network to investigate how these variables impact insect foliar herbivory and the associated carbon, nitrogen, phosphorus, and silica fluxes in forest ecosystems. Over 1 to 2 years, we measured stand-level foliar biomass production, leaf-level herbivory, and foliar element concentrations. At the global scale, insect herbivores liberated higher amounts of elements from the canopies of warmer and drier sites than those of cooler and wetter sites with patterns for phosphorus being most pronounced. MAT exerted a stronger influence over insect-mediated element fluxes than MAP. Foliar biomass production and leaf-level herbivory responses to MAT and MAP were mainly responsible for the observed changes in insect-mediated element fluxes; we also observed minor effects of foliar phosphorus concentration on phosphorus fluxes. Local-scale trends were mixed and successional stage or soil substrate age did not appear to influence insect herbivore-mediated element fluxes. These results demonstrate that climate effects on plant-herbivore interactions are stronger at large than small scales, at which herbivory rates and nutrient fluxes appear to be more strongly affected by a diversity of non-climate factors.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008367","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143762240","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":"Quantifying Soil Gaseous Nitrogen Losses From Nitrification and Denitrification Based on Nitrogen Isotope Model","authors":"Haoming Yu,&nbsp;Wenxin Ba,&nbsp;Peter Dörsch,&nbsp;Wulahati Adalibieke,&nbsp;Yunting Fang,&nbsp;Longfei Yu,&nbsp;Chao Wang,&nbsp;Yihang Duan,&nbsp;Huayan Zhang,&nbsp;Benjamin Z. Houlton,&nbsp;Yan Bo,&nbsp;Yi Wei Jian,&nbsp;Xiao Qing Cui,&nbsp;Edith Bai,&nbsp;Feng Zhou","doi":"10.1029/2024GB008376","DOIUrl":"https://doi.org/10.1029/2024GB008376","url":null,"abstract":"<p>Gaseous nitrogen (N) losses from nitrification and denitrification (NO + N₂O + N₂) pathways contribute a significant fraction of the total N losses from cropland ecosystems. The N mass balance and process-based models are commonly applied to estimate the NO + N₂O + N₂ losses but have suffered from systematic error accumulations or model over-parameterization, leading to a large uncertainty in estimation, hindering effective management of the global N budget. Here, we proposed a novel N isotope model, which considers fertilizer, ammonia volatilization and harvest after testing steady-state assumption of soil δ¹⁵N and N pool for croplands, and justified if it could be successfully applied to constrain NO + N₂O + N₂ losses from cropland ecosystems. We compiled the first bulk-soil δ¹⁵N data set of 0–30 cm soils (<i>n</i> = 738) from croplands and produced a global map of cropland soil δ¹⁵N, which is crucial input data for an isotope model to quantify NO + N₂O + N₂ losses. The results show that the cropland soil δ¹⁵N ranges from 3.5 to 9.0‰, with a mean value of 6.6 ± 0.8‰ (mean ± standard deviation). The estimated NO + N₂O + N₂ losses accounted for an average of 17 ± 9% of N outputs and were 35.86 ± 24.17 kg N ha⁻¹ yr⁻¹ in China's rice paddies, with an increasing trend from Central China to South or North China. The estimations were comparable with the results from observation-constrained denitrification-decomposition modeling (38.9 ± 4.8 kg N ha⁻¹ yr⁻¹) and in good agreement with experimental observations at site scale (<i>R</i>² = 0.58). Our results suggest that soil N isotopes, as a quantitative tracer, provide a valuable alternative approach to constrain the NO + N₂O + N₂ losses in croplands at large geographic scales.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770235","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":"Hydrothermal Plumes Act as a Regional Boundary Sink of 230Th in the Equatorial Pacific","authors":"N. A. Redmond,&nbsp;C. T. Hayes,&nbsp;R. F. Anderson,&nbsp;E. E. Black,&nbsp;R. L. Edwards,&nbsp;M. Q. Fleisher,&nbsp;X. Li,&nbsp;P. J. Lam,&nbsp;K. C. Mateos","doi":"10.1029/2024GB008219","DOIUrl":"https://doi.org/10.1029/2024GB008219","url":null,"abstract":"<p>An important role in the cycling of marine trace elements is scavenging, their adsorption and removal from the water column by sinking particles. Boundary scavenging occurs when areas of strong particle flux drive preferential removal of the trace metals at locations of enhanced scavenging. Due to its uniform production and quick burial via scavenging, ²³⁰Th is used to assess sedimentary mass fluxes; however, these calculations are potentially biased near regions where net lateral transport of dissolved ²³⁰Th violates the assumption that the flux of particulate ²³⁰Th to the seabed equals its rate of production in the water column. Here, we present a water column transect of dissolved ²³⁰Th along 152° W between Alaska and Tahiti (GEOTRACES GP15), where we examine ²³⁰Th profiles across multiple biogeochemical provinces and, novelly, the lateral transport of ²³⁰Th to distal East Pacific Rise hydrothermal plumes. We observed a strong relationship between the slope of dissolved ²³⁰Th concentration-depth profiles and suspended particle matter inventory in the upper-mid water column, reinforcing the view that biogenic particle mass flux sets the background ²³⁰Th distribution in open ocean settings. We find that, instead of the region of enhanced particle flux around the equator, hydrothermal plumes act as a regional boundary sink of ²³⁰Th. At 152° W, we found that the flux-to-production ratio, and thereby error in ²³⁰Th-normalized sediment flux, is between 0.80 and 1.50 for hydrothermal water, but the error is likely larger approaching the East Pacific Rise.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143717292","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":"Modeling Terrestrial Dissolved Organic Carbon and Its Effect on the Carbonate System in the Sunda Shelf Seas, Southeast Asia","authors":"Bernhard Mayer,&nbsp;Stefan Hagemann,&nbsp;Yongli Zhou,&nbsp;Yuan Chen,&nbsp;Shawn Bing Hong Ang,&nbsp;Johannes Pätsch,&nbsp;Patrick Martin","doi":"10.1029/2024GB008433","DOIUrl":"https://doi.org/10.1029/2024GB008433","url":null,"abstract":"&lt;p&gt;The flux of dissolved organic carbon (DOC) from land to sea is an important transfer within the global carbon cycle. The biogeochemical fate of this terrestrial DOC (tDOC) remains poorly understood and is usually neglected in ocean models. Southeast Asia accounts for around 10% of global tDOC flux, mostly from tropical peatland-draining rivers discharging onto the Sunda Shelf. We developed a new light-driven parameterization of tDOC remineralization that accounts for photochemical, microbial, and interactive photochemical–microbial degradation, and simulated the transport and remineralization of tDOC through the Sunda Shelf seas using the regional 3D hydrodynamical HAMSOM and biogeochemical ECOHAM models (only for the carbonate system). Our realistic hindcast simulations for 1958–2022 show that about 50% of riverine tDOC is remineralized before leaving the shelf. This lowers seawater pH across the entire inner Sunda Shelf by an average of 0.005 (by up to 0.05 in the Malacca Strait). Correspondingly, seawater &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;pCO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{pCO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is raised, increasing yearly &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; outgassing from the shelf by 19% (3.1 Tg C &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;yr&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; ${text{yr}}^{-1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, 0.14 mol &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;yr&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","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008433","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143717221","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":"Tracing Pan-Canadian Arctic Water Masses and Dissolved Inorganic Carbon Cycling Using Stable and Radiocarbon Isotopes","authors":"L. Jasperse,&nbsp;B. G. T. Else,&nbsp;L. A. Miller,&nbsp;G. Nickoloff,&nbsp;J. Walker,&nbsp;A. E. Fox,&nbsp;B. D. Walker","doi":"10.1029/2024GB008179","DOIUrl":"https://doi.org/10.1029/2024GB008179","url":null,"abstract":"<p>The Canadian Arctic is warming four times faster than the global average, yet the impact of this perturbation on the marine carbon cycle remains unknown. Dissolved inorganic carbon (DIC) stable isotope (δ¹³C) and radiocarbon (Δ¹⁴C) values are powerful tools for tracing water mass transport, residence times and carbon cycling. While the hydrography of the Canadian Arctic Archipelago (CAA) is well documented, few DIC δ¹³C and Δ¹⁴C values exist for the region. Here, we present new DIC δ¹³C and Δ¹⁴C depth profiles from 19 stations across the CAA sampled in 2021 and place them into the context of five recently published Baffin Bay values. CAA DIC δ¹³C and Δ¹⁴C values ranged from −0.68‰ to +1.86‰, and −90.7 to +49.5‰, respectively. Several negative DIC Δ¹⁴C values (−44.7‰ and −51.9‰) were observed near the Mackenzie River, indicating riverine permafrost carbon is actively incorporated into the nearshore DIC pool. “Bomb” DIC Δ¹⁴C values in the Kitikmeot Sea were attributed to enhanced tidal mixing and heterotrophy together with high regional water mass residence times. A comparison of historical DIC Δ¹⁴C depth profiles from 2009 to 2021 reveals significant dilution of “bomb” ¹⁴C and minor contributions (2.1%–4.4%) of fossil anthropogenic CO₂ within Pacific Summer Water (PSW), Pacific Winter Water (PWW) and Atlantic Fram Strait Water (ATL_FS) in the Beaufort Sea. Finally, the contrast between deep Beaufort Sea and Baffin Bay DIC δ¹³C and Δ¹⁴C values reveal differences in residence time and carbon sources in the two regions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008179","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143707360","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":"Appreciating GBC 2024 Reviewers","authors":"Isaac Santos,&nbsp;Katsumi Matsumoto,&nbsp;Zanna Chase","doi":"10.1029/2025GB008574","DOIUrl":"https://doi.org/10.1029/2025GB008574","url":null,"abstract":"<p>The Editors of the <i>Global Biogeochemical Cycles</i> express their appreciation to those who served as peer reviewers for the journal in 2024.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008574","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698773","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":"Water Column Structure and Nutrient Supply on the Northwest Atlantic Shelf: A Nitrate Isotope Study","authors":"N. Lehmann,&nbsp;M. Kienast,&nbsp;C. Normandeau,&nbsp;P. Thamer,&nbsp;B. Dempsey,&nbsp;B. Thibodeau,&nbsp;C. Buchwald","doi":"10.1029/2024GB008409","DOIUrl":"https://doi.org/10.1029/2024GB008409","url":null,"abstract":"<p>The Northwest Atlantic continental shelf is a highly productive marine region with major uncertainties regarding the supply mechanisms of nutrients fueling productivity. This study uses nitrate isotopes (δ¹⁵N_NO3 and δ¹⁸O_NO3) from the Atlantic Zone Monitoring Program 2020 fall mission and an Optimum Multiparameter Analysis to evaluate on-shelf nutrient transport versus biological supply pathways across three transects from the Laurentian Channel to the central Scotian Shelf. Surface waters showed an imprint of remineralized production, with partial nitrification creating an isotopically light (δ¹⁵N_NO3 ≥2.7‰) surface lens extending from Cabot Strait across the coastal Scotian Shelf. A concurrent enrichment in δ¹⁵N_NO3 and δ¹⁸O_NO3 (&lt;8.5‰, &lt;7.4‰) alongside decreasing nitrate concentrations further indicated phytoplankton assimilation over the deep central shelf (overlying Emerald Basin), a process not observed across Cabot Strait or coastal shelf stations. Subsurface nutrients in Cabot Strait are highly regenerated (&lt;43%), with increased bottom water δ¹⁵N_NO3 signaling sedimentary denitrification in the deep Laurentian Channel. Conversely, subsurface nutrients on the Scotian Shelf were predominantly preformed (&lt;86%), sustained by Cold Intermediate Water from the Gulf of St. Lawrence and warm North Atlantic Central Water (NACW) from offshore. Derived water mass contributions and a distinct isotopically light subsurface layer offshore (δ¹⁵N_NO3 of &gt;4.2‰)−characteristic of N₂ fixation in shallow NACW−indicate a stronger NACW imprint on the central Scotian Shelf compared to the Laurentian Channel and eastern shelf. Our results confirm the importance of slope water advection in supplying subsurface nutrients to the shelf while highlighting the seasonal imprint of recycled production on near-shore surface waters during fall.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008409","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689958","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":"Biological Responses to Ocean Acidification Are Changing the Global Ocean Carbon Cycle","authors":"R. C. Barrett,&nbsp;B. R. Carter,&nbsp;A. J. Fassbender,&nbsp;B. Tilbrook,&nbsp;R. J. Woosley,&nbsp;K. Azetsu-Scott,&nbsp;R. A. Feely,&nbsp;C. Goyet,&nbsp;M. Ishii,&nbsp;A. Murata,&nbsp;F. F. Pérez","doi":"10.1029/2024GB008358","DOIUrl":"https://doi.org/10.1029/2024GB008358","url":null,"abstract":"<p>Increased oceanic uptake of CO₂ due to rising anthropogenic emissions has caused lowered pH levels (ocean acidification) that are hypothesized to diminish biotic calcification and reduce the export of total alkalinity (<i>A</i>_T) as carbonate minerals from the surface ocean or their burial in coastal sediments. This “CO₂-biotic calcification feedback” is a negative feedback on atmospheric CO₂, as elevated levels of surface <i>A</i>_T increase the ocean's capacity to uptake CO₂. We detect signatures of this feedback in the global ocean for the first time using repeat hydrographic measurements and seawater property prediction algorithms. Over the course of the past 30 years, we find an increase in global surface <i>A</i>_T of 0.072 ± 0.023 μmol kg⁻¹ yr⁻¹, which would have caused approximately 20 Tmol of additional <i>A</i>_T to accumulate in the surface ocean. This finding suggests that anthropogenic CO₂ emissions are measurably perturbing the cycling of carbon on a planetary scale by disrupting biological patterns. More observations of <i>A</i>_T would be required to understand the effects of this feedback on a regional basis and to fully characterize its potential to reduce the efficiency of marine carbon dioxide removal technology.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008358","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689955","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":"Chemical Weathering Rates, C-Q Relationships, Fluxes, Dam Impact and pCO2 Potential in the Ganga Headwaters: Insights From Weekly Time-Series Data","authors":"Shaifullah,&nbsp;Indra S. Sen","doi":"10.1029/2024GB008320","DOIUrl":"https://doi.org/10.1029/2024GB008320","url":null,"abstract":"<p>Predicted alterations to the hydrological cycle due to higher temperatures at the end of this century will impact riverine processes such as weathering, erosion, and sediment transport. The Himalayan River basins, with their steep slopes, heavy rainfall, and increasing river engineering projects, are excellent sentinels for monitoring climate change and human impacts on rivers. However, few attempts have been made to capture the river mountainous catchment interaction over shorter time scales (weeks to months) to capture pulses of enhanced chemical weathering rates and other riverine processes. Here, we present a weekly time-series record of dissolved inorganic constituents near the mouth of the Alaknanda and Bhagirathi rivers—the two headwater rivers of the Ganga River—with a weekly resolution during 2018–2019. We report new estimates of discharge-weighted concentrations and fluxes. We found chemical weathering rates of 98.2 ± 54.0 and 32.2 ± 20.4 t/km²/year and CO₂ consumption yields by silicate weathering of 3.7 ± 1.5 × 10⁵ and 1.8 ± 1.2 × 10⁵ mol CO₂/km²/year for the Alaknanda and Bhagirathi basins, respectively, which are significantly higher compared to the global chemical weathering rate and CO₂ consumption yield of ∼24 t/km²/year and ∼1 × 10⁵ mol CO₂/km²/year, respectively. We find that the concentration-discharge relationship shows both chemostatic and dilution trends, with the Tehri dam strongly influencing the hydrology of the Bhagirathi River. The alkalinity-DIC framework reveals that the Himalayan weathering acts as a net source of atmospheric pCO₂ over a timescale of 10⁵–10⁷ years. Further, we show that a sampling campaign spreaded well throughout the year is imperative in reducing uncertainties in flux estimation.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689237","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}