Global Biogeochemical Cycles最新文献

{"title":"High-Resolution Spatiotemporal Analysis of Nitrogen Balance and Use Efficiency in Chinese Annually Planted Cropland (1980–2020)","authors":"Xingxing Duan,&nbsp;Kaikui Cai,&nbsp;Jincheng Li,&nbsp;Man Zhang,&nbsp;Qingsong Jiang,&nbsp;Guozhu Mao,&nbsp;Yue Qin,&nbsp;Zhen Wu,&nbsp;Yong Liu","doi":"10.1029/2026GB009165","DOIUrl":"https://doi.org/10.1029/2026GB009165","url":null,"abstract":"<p>Nitrogen (N) plays a critical role in sustaining global food production and maintaining ecosystem stability. However, the rapid increase in fertilizer use over recent decades has led to excessive N input that surpasses the N uptake capacity of annually planted cropland, thereby imposing substantial environmental pressures. Optimizing annually planted cropland N utilization has thus become an urgent global challenge. In this study, we quantified the spatiotemporal dynamics of N fluxes in Chinese annually planted cropland at a 5-arc-minute resolution from 1980 to 2020 and investigated the factors influencing nitrogen use efficiency (NUE). The results showed that total N input to Chinese annually planted cropland increased markedly during this period, with chemical fertilizer being the dominant source. Concurrently, N output also rose substantially, mainly driven by crop harvests, although its growth rate lagged behind that of N input, resulting in a persistent N accumulation. Spatially, both N input and output were concentrated in intensively cultivated agricultural regions such as North China and the Huang-Huai-Hai Plain, whereas lower values were observed in Northwest and Southwest China. The XGBoost model identified soil thickness, soil organic carbon, and temperature as key determinants of NUE, although their relative importance varied across regions. By employing high-resolution data, this study provides a refined depiction of regional variations in cropland N fluxes and efficiency, overcoming the limitations of previous analyses conducted at administrative scales. The findings offer a robust scientific foundation for improving cropland N management practices and NUE in China, with implications for sustainable agricultural management.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 9","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148860106","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":"Substrate-Specific Potential N2O Production and Hybrid Isotopic Signatures in the Epipelagic Eastern Indian Ocean","authors":"Ting Gu,&nbsp;Zhuo Chen,&nbsp;Jun Sun","doi":"10.1029/2026GB009149","DOIUrl":"https://doi.org/10.1029/2026GB009149","url":null,"abstract":"<p>Nitrous oxide (N₂O) production in epipelagic oligotrophic oceans remains poorly constrained because multiple microbial pathways can co-occur under predominantly oxic conditions and may respond differently to oxygen and substrate availability. Here, we combined multi-substrate ¹⁵N tracer incubations (¹⁵NH₄⁺, ¹⁵N-urea, ¹⁵NO₂⁻, and ¹⁵NO₃⁻), isotopocule-based partitioning of labeled N₂O, and microbial community and genome analyses to investigate pathway-specific potential N₂O production in the epipelagic eastern Indian Ocean. Substrate-specific potential N₂O production exhibited distinct vertical distributions and oxygen responses. Ammonium-, urea-, and nitrite-driven N₂O production generally increased from well-oxygenated waters (&gt;100 μmol L⁻¹ O₂) toward oxycline waters (&lt;100 μmol L⁻¹ O₂), whereas nitrate-driven production showed a non-monotonic response with a maximum at intermediate low-O₂ concentrations of ∼20–50 μmol L⁻¹. Isotopic labeling further revealed widespread hybrid N₂O production, indicating that labeled substrates were coupled with nitrogen intermediates during N₂O production in epipelagic waters. Microbial community patterns and regional genomic potential were consistent with ammonia-oxidizing archaea as candidate contributors to hybrid N₂O production in oxic waters, denitrification-associated taxa near the oxycline, and <i>nosZ</i>-bearing lineages as candidate groups with potential for N₂O reduction. Depth-integrated potential N₂O production was positively related to primary productivity, suggesting that carbon fixation, particle export, and nitrogen remineralization may jointly enhance epipelagic N₂O production. Together, these results provide process-level constraints on oxygen-dependent pathway partitioning of epipelagic N₂O production and highlight a potential carbon-nitrogen linkage whose climatic effect depends on sea-air exchange, water-column transport, and biological N₂O consumption.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 9","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148860062","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":"Beyond the Martin Curve: A Mechanistic Yet Simple Model for Dynamic Ocean Particulate Organic Carbon Fluxes","authors":"Hengdi Liang,&nbsp;Emily J. Zakem,&nbsp;Jonathan M. Lauderdale,&nbsp;Raffaele Ferrari","doi":"10.1029/2026GB009184","DOIUrl":"https://doi.org/10.1029/2026GB009184","url":null,"abstract":"<p>Biological processes contribute to ocean carbon storage, playing a critical role in the global carbon cycle by maintaining lower atmospheric <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>CO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${text{CO}}_{2}$</annotation>\u0000 </semantics></math> levels. A major pathway is the gravitational sinking of particulate organic carbon (POC), yet how POC fluxes change in a warming ocean remains uncertain due, in part, to high spatiotemporal variability in observations. Observed POC fluxes, when averaged, typically exhibit a power-law decrease with depth (the “Martin curve”), yet prognostic models require structural complexity or poorly constrained, empirically tuned parameters to reproduce this behavior. Here, we propose considering the Martin curve as an asymptotic equilibrium benchmark that process-based models should converge to in their long-term, time-averaged behavior. We introduce a simple model for oceanic POC fluxes applicable to the entire water column, grounded in the theory that organic matter remineralization rate scales inversely with its age. We derive an analytical formula linking temporal and vertical variability and evaluate the scheme in an idealized 2D Atlantic Meridional Overturning Circulation model with oscillating surface productivity, which generates time-lagged vertical POC fluxes and dynamic water-column responses while converging to the power-law attenuation in the long term. The results demonstrate that much of the POC flux spatiotemporal variability, including its lack of synchronization with surface productivity and between different depths, can result solely from local surface variability, without invoking complex microbial shifts or lateral advection by ocean currents. This POC flux model enables simulations of ocean carbon cycling across diverse timescales and facilitates model-data comparisons, enhancing our mechanistic understanding of ocean carbon dynamics.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GB009184","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148848725","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":"Influence of Deep-Sea Carbonate Sediments on the Long-Term Durability of Carbon Storage From Ocean Alkalinity Enhancement","authors":"Sina Acksen,&nbsp;Wolfgang Koeve,&nbsp;Markus Pahlow,&nbsp;Christopher J. Somes,&nbsp;Andreas Oschlies","doi":"10.1029/2026GB009203","DOIUrl":"https://doi.org/10.1029/2026GB009203","url":null,"abstract":"&lt;p&gt;Ocean Alkalinity Enhancement (OAE) is a marine carbon dioxide removal (CDR) strategy with a theoretical sequestration potential of several Gt &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{C}mathrm{O}}_{2}$&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;mrow&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;mi&gt;r&lt;/mi&gt;\u0000 &lt;/mrow&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; ${mathrm{y}mathrm{r}}^{-1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. The long-term durability of OAE-induced carbon storage depends on the persistence of the added alkalinity in the ocean, which is influenced by sedimentary processes and biogeochemical and physical feedbacks. Using the University of Victoria v2.10 Earth System Model of intermediate complexity, we investigated the millennial-scale durability of OAE-induced extra alkalinity and associated additional carbon storage and, specifically, the role of deep-sea calcium carbonate sediments in limiting the durability. We conducted 10,000-year simulations for four emissions scenarios, each combined with a global alkalinity addition experiment (0.135 Pmol &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; for 50 years) with and without interactive carbonate sediments. Neither the added alkalinity nor the associated oceanic carbon storage remained fully stable on millennial timescales compared to a baseline simulation. By year 10,000, 35%–59% of the initial alkalinity increase through OAE is lost due to &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;CaCO&lt;/mtext&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CaCO}}_{3}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; dynamics in deep-sea sediments, resulting in a reduction of the OAE-induced carbon storage by 14%–27% compared to simulations without &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 ","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GB009203","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783639","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":"Magnitude and Drivers of Nitrous Oxide Emission Pulses Over the Seasonal Transition: A Synthesis","authors":"Yunyao Zhong,&nbsp;Yanzhong Yao,&nbsp;Bingbing Han,&nbsp;Xunzhuo Dong,&nbsp;Mengfei Li,&nbsp;Shuli Niu,&nbsp;Zhaolei Li","doi":"10.1029/2026GB009249","DOIUrl":"https://doi.org/10.1029/2026GB009249","url":null,"abstract":"<p>The magnitude of nitrous oxide (N₂O) emission pulses during the winter-to-spring seasonal transition (ST) can exceed summer peaks, but this component remains poorly constrained in the global N₂O budget. Here, we conducted a synthesis of 182 observations without fertilizer applications using machine-learning, hierarchical mixed-effects models, and structural equation modeling to compare ST-N₂O pulse magnitude and identify its dominant drivers. The average rate of ST-N₂O pulse was 63.2 μg m⁻² hr⁻¹, approximately 3.5 times higher than that during the growing season. Moreover, the average ST-N₂O pulse was 108.2 mg m⁻² in non-croplands, which is 2.4 times greater than that in croplands without nitrogen fertilizer (46 mg m⁻²). ST-N₂O pulse was influenced by the microbial vernal dam (MVD, defined as the seasonal release of microbial biomass nitrogen), microbial biomass carbon, soil respiration rate, and ammonium content. Soil MVD emerged as the dominant driver of ST-N₂O pulse across ecosystem types, accounting for 21% of the observed variation. Cumulative ST-N₂O pulses accounted for 2.9% of the nitrogen derived from MVD. These results highlight a ubiquitous hot moment in terrestrial N₂O emissions and provide a mechanistic basis for improving annual N₂O budgets and model parameterization.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783640","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":"Drivers and Patterns of Sediment Organic Carbon in European Regional Seas","authors":"Christian Lønborg,&nbsp;Anna Elizabeth Løvgren Graversen,&nbsp;Anna Maria Addamo,&nbsp;Jorge Assis,&nbsp;Michael Timothy Burrows,&nbsp;Eleanor Stewart,&nbsp;Helen Lillis,&nbsp;Mark John Costello,&nbsp;Dorte Krause-Jensen","doi":"10.1029/2026GB009100","DOIUrl":"https://doi.org/10.1029/2026GB009100","url":null,"abstract":"<p>Mapping organic carbon (OC) stores in marine sediments is a management priority to potentially minimize the anthropogenic release of organic carbon from the seabed. Sediment OC content shows high regional variability, shaped by a complex interplay of physical, chemical, biological and anthropogenic factors. In this study, we present an assessment of the drivers and patterns of sediment OC across European regional seas, with a particular focus on the role of large-scale habitats, substratum characteristics, and environmental conditions. To investigate these relationships, we integrated data sets encompassing sediment OC, benthic habitats, sediment substrata and 11 environmental variables. Applying machine learning techniques, we identified wave exposure (estimated from wave fetch), light availability, seafloor geomorphic features, and maximum bottom water temperature as the most important environmental predictors of sediment OC content across European regional seas. While the model captured broad spatial patterns in sediment OC, it did not resolve local scale variability, making it better suited for regional assessments than for site-specific predictions. Overall, the highest OC contents were found in sediments underlying vegetated habitats such as <i>Posidonia</i> <i>oceanica</i> and other seagrass meadows as well as in mud, and mixed sediment substrata. OC hotspots were generally located in inshore areas with low wave fetch and temperature; these include areas of the Baltic Sea, North Sea, Adriatic Sea, Barents Sea, and the Black Sea. Our data-driven approach provides a robust foundation for identifying OC-rich sediments, which are critical for conservation planning and assessing anthropogenic impacts on marine OC.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GB009100","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148784036","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-Resolution Particle Imaging Reveals the Importance of Phytodetrital Aggregate Flux and Mesopelagic Grazing for Carbon Storage in the Southern Ocean","authors":"S. H. O’Daly,&nbsp;G. M. M. Hennon,&nbsp;T. B. Kelly,&nbsp;R. Kiko,&nbsp;R. M. Lekanoff,&nbsp;J. L. Pretty,&nbsp;S.-M. Schröder,&nbsp;A. M. P. McDonnell","doi":"10.1029/2025GB008685","DOIUrl":"https://doi.org/10.1029/2025GB008685","url":null,"abstract":"<p>The biological, chemical, and physical processes in the mesopelagic zone that impact carbon flux to the deep ocean are poorly understood, particularly in the Southern Ocean, despite their importance to deep ocean carbon storage. Using a CTD-mounted underwater imaging system, the Underwater Vision Profiler 5, we observed distributions of large marine particles across two basin-scale global ocean ship-based hydrographic investigations program repeat hydrography transects in the Pacific and African sectors of the Southern Ocean. Utilizing deep learning features and unsupervised clustering, 2.6 million images of particles were classified by type into 46 detrital categories within four supercategories (e.g., fluffy aggregates, dense aggregates, fibers, feces) and 61 living categories within four supercategories (e.g., crustaceans, rhizarians, gelatinous zooplankton, <i>Trichodesmium</i>). Different frontal zones generally have distinct patterns in particles, which illuminate different flux pathways. We observed a “Fluffy Aggregate Flux Pathway”, where high fluffy aggregate abundance was observed from the surface to 3,000 m at the same time as elevated surface chlorophyll <i>a</i>. We also observed a “Zooplankton Mediated Flux Pathway,” where grazers were located primarily in the lower mesopelagic zone, and feces and dense aggregates were in high abundance in the abyssopelagic zone. These results highlight two export pathways in the Southern Ocean, both of which contribute to long-term carbon storage at depth.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008685","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753867","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":"Declining Contribution of Nitrogen Deposition to the Interannual Variability of Terrestrial Gross Primary Productivity","authors":"Shiliang Chen,&nbsp;Bin Chen,&nbsp;Shaoqiang Wang,&nbsp;Li Zhang,&nbsp;Jiageng Ma,&nbsp;Zhenhai Liu,&nbsp;Jinghua Chen","doi":"10.1029/2026GB009129","DOIUrl":"https://doi.org/10.1029/2026GB009129","url":null,"abstract":"<p>Global nitrogen deposition has steadily increased since the 1980s, peaking around 2015 before stabilizing. However, atmospheric chemical transport models often underestimate its magnitude, limiting accurate assessments of its impacts on terrestrial gross primary productivity (GPP). In this study, we elucidated the drivers of interannual GPP variability and quantified the contribution of nitrogen deposition from 1980 to 2020 using the latest global nitrogen deposition data set, the TRENDY GPP products, and an interpretable machine learning framework (SHAP). Our findings revealed a consistent expansion in global GPP over the past four decades, averaging 156.95 ± 6.4 Pg C yr⁻¹. As nitrogen deposition has recently stabilized, its contribution to global GPP has shifted from a stimulatory effect to a source of negative fluctuations. This transition is attributable to the declining sensitivity of GPP to nitrogen deposition, potentially driven by increasing vegetation water stress. Climatic factors, primarily temperature and precipitation, dominate interannual GPP fluctuations across plant functional types (PFTs), and nitrogen deposition explains 8.7 ± 2.9% of global variability. Notably, nitrogen enrichment stimulated GPP in grasslands and croplands but had an inhibitory effect on tropical forests. Moreover, the nonlinear response of GPP to nitrogen deposition exhibited distinct optimal thresholds across PFTs, with the global vegetation optimum identified at 12.5 kg N ha⁻¹ yr⁻¹. Crucially, the direct effect of nitrogen deposition on GPP outweighed its synergistic interactions with climate and CO₂ concentrations, suggesting that nitrogen availability independently modulates terrestrial carbon sinks. This study underscores the biome-specific sensitivities to nitrogen loading and highlights the necessity of incorporating nitrogen-saturation thresholds into predictions of ecosystem feedback to global change.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148754092","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":"Interhemispheric Asymmetry in Air-Sea CO2 flux Trends Across Eastern Boundary Current Systems Under a High Warming Scenario","authors":"Priyanka Banerjee,&nbsp;S. Prasanna Kumar","doi":"10.1029/2025GB008860","DOIUrl":"https://doi.org/10.1029/2025GB008860","url":null,"abstract":"<p>Eastern boundary current systems (EBCSs) transport cold, carbon-rich polar waters toward the equator. Wind-driven coastal upwelling within EBCSs fuels intense biological activity, modulating upper ocean pH, middepth oxygen levels, and carbon cycling. While past studies have primarily examined upwelling dynamics and productivity responses to climate change, the future of carbon uptake in EBCSs remains poorly understood. Using results from multiple Earth system models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we show that during 2015–2100 the Southern Hemisphere EBCSs are projected to experience significantly greater positive trends in air-sea CO₂ flux (F_CO2), implying stronger uptake or reduced outgassing of CO₂, compared to their Northern Hemisphere counterparts. Such asymmetry arises from weakening of EBCSs owing to greater poleward shifts of the subtropical gyres over the Southern Hemisphere compared to the Northern Hemisphere. These changes enhance the poleward advection of warm tropical waters while suppressing the supply of carbon-rich waters from high latitudes by the EBCSs, thereby increasing (reducing) upper ocean CO₂ uptake (outgassing) in the EBCSs despite complex upwelling trends. Across the CMIP6 models, there exists a consistent link between the magnitude of poleward shifts of the subtropical gyres and the magnitude of positive F_CO2 trends in the EBCSs. Our findings reveal a robust interhemispheric contrast in carbon uptake, offering new insights into how large-scale circulation shifts influence both global and regional carbon budgets.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753625","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":"CbPM Estimates of Net Primary Production in the North Atlantic From Profiling Floats and Satellites Diverge Seasonally Due To Fluorescence and Vertical Extrapolation Effects","authors":"Nina Buzby,&nbsp;Andrea J. Fassbender,&nbsp;Alison R. Gray,&nbsp;Marin Cornec,&nbsp;Jacki Long,&nbsp;Ellen Park","doi":"10.1029/2025GB008952","DOIUrl":"https://doi.org/10.1029/2025GB008952","url":null,"abstract":"<p>Marine net primary production (NPP), defined as the difference between gross production and phytoplankton respiration, is often estimated using algorithms applied to remote sensing data. While assumptions are needed to extend surface satellite observations through depth, some NPP algorithms, like the Carbon-based Productivity Model (CbPM), have been adapted to vertically resolved data collected by autonomous profiling floats. Such applications eliminate the need for vertical extrapolation but introduce challenges related to float measurements of fluorescence rather than chlorophyll-<i>a</i> (Chl-<i>a</i>; required CbPM input). This study analyzes over a decade of float observations from the North Atlantic to estimate NPP using CbPM and quantify its sensitivity to different input parameters: (a) fluorescence versus Chl-<i>a</i>, (b) vertically extrapolated versus depth-resolved information, and (c) in situ versus remote observations of the first optical depth—the impacts of which vary seasonally and regionally. In higher latitude waters, converting float fluorescence to Chl-<i>a</i> using a novel correction based on satellite data produces significantly smaller NPP estimates at seasonal and annual timescales. In contrast, extrapolation and platform-related differences largely compensate when integrated vertically and annually, such that cumulative annual depth-integrated NPP (iNPP) estimates computed with fluorescence-corrected float measurements are statistically indistinguishable from those extrapolated from satellite observations. These effects are reversed in the subtropics: discrepancies due to fluorescence compensate vertically and annually, whereas annual iNPP estimates from depth-resolved float measurements significantly outweigh those of satellites. Seasonal changes to the sign, timing, and vertical structure of NPP discrepancies suggest persistent sub-seasonal disagreement between platforms, highlighting knowledge gaps in understanding NPP.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"40 8","pages":""},"PeriodicalIF":6.9,"publicationDate":"2026-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008952","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753177","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}