Global Biogeochemical Cycles最新文献

{"title":"Faster Soil Carbon Aging With Depth at Higher Elevations in a Subtropical Forest","authors":"Wanshu Li,&nbsp;Jing Wang,&nbsp;Huanfa Sun,&nbsp;Ning Wei,&nbsp;Liming Yan,&nbsp;Jian Zhang,&nbsp;Jianyang Xia","doi":"10.1029/2025GB008633","DOIUrl":"https://doi.org/10.1029/2025GB008633","url":null,"abstract":"<p>Earth system models are increasingly adopting multi-layer soil frameworks to improve simulations of vertical carbon distribution. A critical parameter in these models is the <i>e</i>-folding depth (<i>z</i>_<i>τ</i>), which quantifies the rate at which soil organic carbon (SOC) ages with depth. Specifically, <i>z</i>_<i>τ</i> represents the soil depth at which carbon becomes <i>e</i>-times older (≈2.7 times older) than surface carbon. Despite its importance, most models assume constant <i>z</i>_<i>τ</i> within biomes, leaving its spatial variability largely unclear. To test this assumption, we collected multi-layer soil samples across eight forest plots spanning a subtropical montane elevational gradient (427–1,474 m) and employed radiocarbon dating to quantify vertical SOC aging patterns. Our results revealed a robust exponential increase in SOC age with depth at all elevations, alongside a 66% decline in <i>z</i>_<i>τ</i> from 78.6 cm at the base to 26.4 cm at the summit. This indicated that a 1-m increase in soil depth approximately amplified SOC age by 4-fold at the lowest elevation and 44-fold at the highest position. Despite significant changes in vegetation along the elevational gradient, vegetation type did not play an essential role in controlling <i>z</i>_<i>τ</i> variability. Instead, this elevational dependence of <i>z</i>_<i>τ</i> was primarily driven by soil water content (22.2% of variability explained), mean annual temperature (19.7%), and soil carbon-to-nitrogen ratio (19.0%). These findings suggest <i>z</i>_<i>τ</i> as an elevation-sensitive sentinel of soil carbon dynamics, urging models to incorporate its variability for projections of soil carbon persistence under climate change.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317424","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":"Compound Marine Heatwaves and Acidity Extremes in the Southern Ocean","authors":"Joel Wong,&nbsp;Matthias Münnich,&nbsp;Nicolas Gruber","doi":"10.1029/2025GB008630","DOIUrl":"https://doi.org/10.1029/2025GB008630","url":null,"abstract":"<p>Compound extremes of temperature and acidity that extend over substantial fractions of the water column can be particularly damaging to marine organisms, as they experience not only additional stress by the potentially synergistic effects of these two stressors, but also a reduction in habitable vertical space. Here, we detect and analyze such column-compound extremes (CCX) in the Southern Ocean between 1980 and 2019, and characterize their duration, intensity, and spatial extent. To this end, we use daily output from a hindcast simulation of the Regional Ocean Modeling System (ROMS), coupled with the Biological Elemental Cycling (BEC) model. We first detect extremes in temperature and acidity ([<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>H</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{H}}^{+}$</annotation>\u0000 </semantics></math>]) within the top 300 m using a relative threshold of 95% and then identify CCX where conditions are extreme for both stressors for at least 50 m of the water column. When analyzed on a fixed baseline, positive trends in ocean warming and acidification caused CCX to last longer, intensify, and expand throughout the Southern Ocean. In the Antarctic zone, CCX expanded between 1980 and 2019 more than ten times in volume, lasted up to 120 days longer, and doubled in anomaly. Some of the largest and longest events occurred in Antarctic Marine Protected Areas (MPAs), covering more than 200,000 km² and persisting for over 500 days. CCX in the Subantarctic and Northern zones quadrupled in volume and increased by more than 30% in anomaly. Across the Southern Ocean, the increasing occurrence of CCX exacerbates the risks to marine ecosystems from warming and acidification.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008630","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317454","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":"Regulation of Mesoscale Eddies on Oceanic Methane Production, Oxidation, and Emissions","authors":"Xiao-Jun Li,&nbsp;Shuang Li,&nbsp;Xu-Xu Gao,&nbsp;Jian-Long Li,&nbsp;Feng Xu,&nbsp;Chun Zhou,&nbsp;Hong-Hai Zhang,&nbsp;Guang-Chao Zhuang","doi":"10.1029/2025GB008500","DOIUrl":"https://doi.org/10.1029/2025GB008500","url":null,"abstract":"<p>The ocean is a source of atmospheric methane (CH₄), yet the impact of mesoscale processes on CH₄ cycling remains largely unconstrained. In this study, we combined high-resolution underway observations and site-specific geochemical analyses conducted in September 2020, with methane oxidation (MOx) rates measurements and molecular analysis in September 2022, to investigate the regulation of mesoscale eddies on CH₄ production, methanotrophic activity, and emission fluxes in the South China Sea (SCS). Underway observation revealed that cyclonic eddies (CEs) increased surface CH₄ concentrations, while anticyclonic eddies (AEs) generally exhibited lower CH₄ levels. CEs observed in September 2020 after summer, enhanced CH₄ production associated with phytoplankton by transporting coastal nitrate-rich waters into the eddy core. Particulate dimethylsulfoniopropionate (DMSP_p) produced by phytoplankton was identified as a significant source of CH₄ within the mixed layer based on the significant correlations between DMSP and CH₄ (<i>r</i> = 0.79<i>; p</i> &lt; 0.01). In contrast, elevated MOx rates and <i>pmoA</i> gene abundance were observed in the AEs, driven by convergence and stratification of surface seawater caused by downwelling of water masses. Compared to reference sites, the CH₄ air–sea fluxes in CEs increased by 204%, whereas the CH₄ emission flux in AEs was reduced by 25.1%. Collectively, mesoscale eddies significantly influence CH₄ cycle by altering phytoplankton composition, nutrient dynamics and microbial communities, ultimately leading to the divergent CH₄ emissions. Our results illustrated the control of mesoscale eddies on CH₄ production and oxidation and highlighted the importance of physical processes on biogeochemical cycling and greenhouse gas emissions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317503","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":"Temporal Decoupling Between Total Organic Carbon and Iron in Lakes Linked to Interannual Changes in Precipitation","authors":"Aleksey Paltsev,&nbsp;Irena F. Creed,&nbsp;Dag O. Hessen,&nbsp;Stina Drakare,&nbsp;Danny C. P. Lau,&nbsp;Tobias Vrede,&nbsp;Pirkko Kortelainen,&nbsp;Kristiina Vuorio,&nbsp;Kimmo K. Kahilainen,&nbsp;Heleen A. de Wit,&nbsp;Peter D. F. Isles,&nbsp;Anders Jonsson,&nbsp;Erik Geibrink,&nbsp;Jussi Vuorenmaa,&nbsp;Ann-Kristin Bergström","doi":"10.1029/2025GB008520","DOIUrl":"https://doi.org/10.1029/2025GB008520","url":null,"abstract":"<p>Widespread increases in lake browning, which affects primary production, have been observed in northern lakes. While lake browning is attributed to increases in terrestrially derived total organic carbon (TOC) and total iron (Fe), Fe does not consistently correlate with increasing TOC over time. This temporal mismatch between TOC and Fe indicates that we still do not fully understand the causes of lake browning, especially in the context of gradually changing climatic conditions. In this study, we utilized Fennoscandian 30-year (1990–2020) time series data for 102 lakes to describe possible reasons for the temporal decoupling between TOC and Fe. Using Bayesian mixed-effects models and wavelet coherence analysis, we found evidence for differential responses of TOC and Fe concentrations to changes in precipitation, temperature, and sulfur deposition. While TOC appeared more sensitive to the effects of precipitation, temperature and sulfur deposition in individual lakes, Fe concentrations were impacted by complex interactions among these environmental variables. Although TOC and Fe increased in most lakes in response to increased temperature and precipitation, 41% of the lakes—typically with larger catchment-to-lake area ratios and shorter water residence times—exhibited a declining trend in Fe. This analysis encompasses lakes of both significant and non-significant changes over time. This decline in Fe was associated with short-timescale (2–4 years) increases in precipitation, leading to a temporal decoupling between Fe and TOC. Our findings suggest that Fe concentrations do not increase uniformly with rising temperatures and increased precipitation, especially in regions where sulfur deposition has declined due to atmospheric recovery policies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008520","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317272","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":"High Lithogenic and Micro-Nutrient Fluxes From the West Greenland Margin Traced by Thorium in Seawater and Sediments","authors":"George H. Rowland,&nbsp;Katharine R. Hendry,&nbsp;Amber L. Annett,&nbsp;Hong Chin Ng,&nbsp;Laura F. Robinson,&nbsp;Robert M. Sherrell,&nbsp;Yuxin Zhou,&nbsp;Jerry F. McManus,&nbsp;J. Alexander Brearley,&nbsp;Tao Li","doi":"10.1029/2025GB008531","DOIUrl":"https://doi.org/10.1029/2025GB008531","url":null,"abstract":"<p>The flux of nutrients from continents to the oceans sustains oceanic primary productivity and is a fundamental component of the carbon cycle. In most regions of the world's oceans primary productivity is limited by the supply of nutrients. In particular, iron can become limiting in the open-ocean due to its low solubility. Glaciated continents have been suggested as an underappreciated source of iron to the high-latitude oceans. Yet, uncertainty remains regarding the magnitude and spatial variability of glacially derived nutrient fluxes, and the extent to which these nutrients impact open-ocean ecosystems. To quantify lithogenic fluxes at the West Greenland margin, we measured ²³²Th and ²³⁰Th in seawater and core-top sediments across the shelf and slope. Our results highlight a negative correlation between low-salinity waters and dissolved and particulate ²³²Th, suggesting a glacial source for this lithogenic isotope. We calculated dissolved ²³²Th fluxes 5–24 μg m⁻² yr⁻¹ (100–500 m depth), and sedimentary ²³²Th fluxes 105–711 μg m⁻² yr⁻¹, higher than typical open-ocean settings and similar to margin sites influenced by large inputs from aeolian dust and rivers. A sampling transect shows that dissolved ²³²Th fluxes increase toward Greenland, confirming that lithogenic inputs are sourced laterally from the margin. Using our ²³²Th fluxes, we estimate an elevated supply of dissolved Fe which extends over the continental slope toward the open ocean. This Fe flux is large enough to support much of the local primary productivity, highlighting the importance of lithogenic fluxes in supporting the marine ecosystem in high-latitude oceans.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008531","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316712","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":"Methane and Nitrous Oxide Budgets for Australasia: A Regional Assessment of Natural and Anthropogenic Sources and Sinks","authors":"Yohanna Villalobos,&nbsp;Josep G. Canadell,&nbsp;Elizabeth D. Keller,&nbsp;Peter R. Briggs,&nbsp;Phillip Ford,&nbsp;Ian N. Harman,&nbsp;Timothy W. Hilton,&nbsp;Allison Hogikyan,&nbsp;Ronny Lauerwald,&nbsp;Damien T. Maher,&nbsp;Adrien Martinez,&nbsp;Naiqing Pan,&nbsp;Benjamin Poulter,&nbsp;Laure Resplandy,&nbsp;Judith A. Rosentreter,&nbsp;Marielle Saunois,&nbsp;Hanqin Tian,&nbsp;Jacob Yeo,&nbsp;Zhen Zhang","doi":"10.1029/2024GB008484","DOIUrl":"https://doi.org/10.1029/2024GB008484","url":null,"abstract":"<p>We present the CH₄ and N₂O budgets for anthropogenic and natural sources and sinks of Australasia (Australia and New Zealand) from 2010 to 2019 using bottom-up and top-down methods, in line with the RECCAP-2 initiative, with extensions to 2022. We show that the bottom-up CH₄ budget for Australasia (2010–2019) was a net source of 14.1 ± 5.5 Tg CH₄ yr⁻¹, with Australia and New Zealand contributing 84% and 16%, respectively. Anthropogenic sources contributed 55% of all CH₄ emissions, the rest coming from natural sources, primarily wetlands. The bottom-up N₂O budget was a net source of 0.5 ± 0.3 Tg N₂O yr⁻¹, with Australia contributing the majority (92%), mainly from natural sources (82%). Australasia top-down CH₄ (10.4 ± 0.5 Tg CH₄ yr⁻¹) and N₂O budgets (0.8 ± 0.5 Tg N₂O yr⁻¹) differ in magnitude from the bottom-up budgets but remain consistent within their uncertainties. Similar consistency is observed for Australia, while New Zealand shows significant discrepancies, particularly for N₂O, where the bottom-up estimate is 71% higher than the top-down estimate. In terms of trends, bottom-up natural wetland CH₄ emissions increased in both countries between 2010 and 2019. CH₄ emissions from enteric fermentation slightly declined in Australia but increased in New Zealand. Soil N₂O emissions from nitrogen additions increased in both countries, with a significant rise in New Zealand driving the overall positive trend in anthropogenic emissions. These findings highlight critical sectors with large mitigation potential and the significance of monitoring natural sources for possible biogeochemical-climate feedback.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008484","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316689","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":"The Contribution of Deep Chlorophyll Maxima to Net Primary Production in the Southern Ocean","authors":"Clara R. Vives,&nbsp;Christina Schallenberg,&nbsp;Peter G. Strutton,&nbsp;Jørgen Bendtsen,&nbsp;Katherine Richardson,&nbsp;Philip W. Boyd","doi":"10.1029/2024GB008327","DOIUrl":"https://doi.org/10.1029/2024GB008327","url":null,"abstract":"<p>Deep chlorophyll maxima (DCMs) have long been studied in the northern hemisphere but have received less attention in the Southern Ocean. Their contribution to phytoplankton biomass and net primary productivity (NPP) is poorly resolved. Recently, the application of satellite NPP algorithms to biogeochemical (BGC)-Argo float data has improved vertically resolved NPP estimates. Using this approach on 12,700 BGC-Argo profiles south of 30°S, we report (1) subsurface (below the mixed layer) estimates of NPP, (2) the contribution of subsurface NPP to total NPP, and (3) the influence of DCMs and deep biomass maxima (DBMs) on (1) and (2). When DCMs are present (<i>n</i> = 2,119 profiles), subsurface NPP is 217 ± 106 mg C m⁻² day⁻¹ compared to 82 ± 92 mg C m⁻² day⁻¹ for all profiles. We further compare observations across seasons in four water masses from nitrate-limited oligotrophic waters north of the subtropical front to iron-limited regions further south, including the sea ice zone. Low-latitude DCMs (i.e., 30–44°S), show the highest contribution to column-integrated NPP. However, DCMs occur across all frontal zones and contribute significantly to total NPP when present. Rather than missing subsurface NPP associated with DCMs, the satellite Carbon-based Productivity Model (CbPM) tends to mistakenly assume DCMs below the mixed layer, overestimating NPP. This situation is somewhat ameliorated in the ferricline version of the CbPM due to better nutricline-euphotic depth alignment. Our results highlight the importance of understanding the vertical structure of phytoplankton stocks and productivity, with direct impacts on global NPP estimates and, ultimately, climate model projections.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008327","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145272190","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":"Global “Climate Opportunity Benefit” of Forest Regeneration: Meta-Analysis Shows Warming From Soil CH4 and N2O Is Small Relative to Agriculture","authors":"Savannah S. Cooley,&nbsp;Elisabeth Moore,&nbsp;Jianna Martinez,&nbsp;Jocelyn Fahlen,&nbsp;Erin Maybach,&nbsp;Maya Gollerkeri,&nbsp;Anjali Rao Vasa,&nbsp;Sian Kou-Giesbrecht,&nbsp;Alexandra M. Huddell,&nbsp;Linnea Norton,&nbsp;Kerry Cawse-Nicholson,&nbsp;Ruth DeFries,&nbsp;Maria Uriarte,&nbsp;Duncan N. L. Menge","doi":"10.1029/2024GB008446","DOIUrl":"https://doi.org/10.1029/2024GB008446","url":null,"abstract":"<p>Global assessments of ecosystem regeneration as a climate mitigation strategy have traditionally focused on CO₂, despite the acknowledgment that methane (CH₄) and nitrous oxide (N₂O) are also important greenhouse gases (GHGs). We conducted a meta-analysis of studies that measured soil CH₄ and N₂O fluxes in unmanaged, regenerating forested and savanna ecosystems, with a focus on understanding biome-specific differences in these GHG fluxes compared to a counterfactual of agricultural land use. We expected most regenerating ecosystems to act as small CH₄ sinks and relatively larger N₂O sources, with a net warming combined CH₄-N₂O effect. Three of the five forested biomes we studied followed this pattern: subtropical/tropical forest, subtropical/tropical savanna and temperate conifer forest (0.60 ± 0.30, 0.15 ± 0.06, and 0.83 ± 0.24 Mg CO₂e ha⁻¹ yr⁻¹, respectively). Results suggest that even after 100 years of regeneration, the radiative cooling of the climate from CO₂ sequestration in aboveground biomass exceeds the radiative warming driven by the net CH₄-N₂O effect among all ecosystems on average globally. We also found that the “climate opportunity benefit” of ecosystem regeneration—the difference in the net CH₄-N₂O effects of agriculture versus regeneration—yields a net cooling effect for all biomes. However, because the CH₄-N₂O effect diminishes the cooling effect of ecosystem regeneration, our results underscore that it is unsound to use ecosystem regeneration as a justification for continuing fossil fuel emissions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145271826","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":"Atmospheric Deposition, Shelf Sediment Supply, Riverine Input, and Redox Conditions Control Dissolved Manganese in the Indian Ocean","authors":"Nirmalya Malla,&nbsp;Sunil Kumar Singh","doi":"10.1029/2025GB008660","DOIUrl":"https://doi.org/10.1029/2025GB008660","url":null,"abstract":"<p>Dissolved manganese (dMn) is an essential bioactive element required for marine organisms. Redox condition determines its solubility and its solid phase removal from seawater. It displays a typical scavenging type profile in the Indian Ocean with an elevated concentration in the Oxygen Minimum Zone (OMZ) of the Bay of Bengal (BoB). The surface dMn decreases southward in the BoB, and its concentration gradient correlates well with salinity because of the enormous riverine influx. Reductive dissolution of Iron-manganese (Fe-Mn) oxyhydroxides-rich sediments brought by the Ganga-Brahmaputra rivers enriches dMn in the bottom waters of the shelf regions (∼25 nM), which gets advected to the open ocean through cross-shelf transport. The atmospheric input is the prominent source of dMn in the BoB. Transport of the Indonesian Through Flow waters supplies high dMn in the surface waters of the Central Indian Ocean Basin. Internal cycling seems to control the dMn distribution in the water column in addition to its external sources. Water column denitrification increases dMn in the OMZ waters of the BoB through the reductive dissolution of sinking Mn oxide particles under the prevailing suboxic conditions. The presence of two sub-surface peaks of dMn associated with nitrite maxima suggests active denitrification in the OMZ waters of the BoB, similar to the Arabian Sea. The interaction of circulating fluid with subducting Fe-Mn-rich crusts enriches the deep water dMn in the Java Sumatra region. Further, the hydrothermal activity over the Southeast and Central Indian Ridges contributes significantly to the dMn budget of the deeper waters.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145271825","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":"BGC-Argo Floats Reveal Nitrite and Thiosulfate Dynamics in the Oceans With High Spatiotemporal Resolution","authors":"Mariana B. Bif,&nbsp;Kenneth S. Johnson","doi":"10.1029/2024GB008473","DOIUrl":"https://doi.org/10.1029/2024GB008473","url":null,"abstract":"<p>Marine oxygen deficient zones (ODZs) play a major role in the Earth's biogeochemical cycles and are responsible for nitrogen and sulfur removal from the oceans. Microbial-reducing reaction processes generate nitrite (NO₂⁻) and sulfur compounds as intermediaries that may accumulate in these zones. Current assessments on microbial transformations inside ODZs are based on shipboard measurements, and there are no well-resolved seasonal to annual observations or high-resolution vertical sampling that would characterize variability. Here, we propose an alternative statistical approach to analyze the raw output of the nitrate sensor from BGC-Argo floats with the ability to detect NO₂⁻ and thiosulfate (S₂O₃²⁻) concentrations in addition to nitrate. The new approach provides data with great vertical and spatiotemporal resolution. The method can be applied to UV-spectrometer output data from SUNAs and ISUS nitrate sensors commonly deployed on various observing platforms. We validated the technique in the field by matching shipboard NO₂⁻ bottle data with float data from the Eastern Tropical North Pacific (ETNP) and Eastern Tropical South Pacific (ETSP) ODZs. We then show a complete time series of three floats as study cases. The ability to detect NO₂⁻ and S₂O₃²⁻ concomitantly with other key chemical variables (i.e., oxygen, pH, and bio-optics) at such fine scale allows for novel insights into the nitrogen and sulfur cycling of ODZs and processes driving these cycles. This new approach will enable fine-scale remote quantification of NO₂⁻ and S₂O₃²⁻ to support a better understanding of the biogeochemical transformations happening inside these already-expanding deoxygenated regions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008473","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145224125","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}