Global Biogeochemical Cycles最新文献

{"title":"Surface and Subsurface Compound Marine Heatwave and Biogeochemical Extremes Under Climate Change","authors":"Natacha Le Grix,&nbsp;Friedrich A. Burger,&nbsp;Thomas L. Frölicher","doi":"10.1029/2025GB008514","DOIUrl":"https://doi.org/10.1029/2025GB008514","url":null,"abstract":"<p>Marine species are increasingly threatened by extreme and compound events, as warming, deoxygenation, and acidification unfold. Yet, the surface and especially the subsurface distribution and evolution of such compound events remain poorly understood. We present the current and projected distributions of compound marine heatwave (MHW), low oxygen (LOX), and high acidity (OAX) events throughout the water column, using observation-based data from 2004 to 2019 and large ensemble Earth system model simulations from 1890 to 2100. Our findings reveal that compound MHW-OAX and OAX-LOX events are prevalent in the low to mid latitudes at the ocean surface. At 200 and 600 m, MHW-OAX and MHW-LOX events are frequent in the high latitudes and parts of the tropics, while OAX-LOX events occur globally. Subsurface compound events are often associated with vertical displacements of water masses, with the climatological vertical gradients of ecosystem stressors typically explaining their occurrence patterns. Projections show a strong rise in compound event frequency over the historical period and under continued global warming, primarily driven by shifts in mean oceanic conditions. The portion of the top 2,000 m affected by extreme or compound events rises from 20<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $%$</annotation>\u0000 </semantics></math> to 98<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $%$</annotation>\u0000 </semantics></math> under 2°C of global warming in a high emissions scenario using a preindustrial baseline, and to 30<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $%$</annotation>\u0000 </semantics></math> using a shifting-mean baseline. However, physical and biogeochemical changes may also lead to regional decreases in subsurface events, highlighting complexities in how warming, deoxygenation, and acidification unfold in the ocean interior. Increasing compound event frequency poses a major threat to marine ecosystems, potentially disrupting food webs and biodiversity.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008514","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143883917","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":"Southern Ocean Carbon Export Revealed by Backscatter and Oxygen Measurements From BGC-Argo Floats","authors":"Guillaume Liniger,&nbsp;Sébastien Moreau,&nbsp;Delphine Lannuzel,&nbsp;Magdalena M. Carranza,&nbsp;Peter G. Strutton","doi":"10.1029/2024GB008193","DOIUrl":"https://doi.org/10.1029/2024GB008193","url":null,"abstract":"<p>The Southern Ocean (south of 30°S) contributes significantly to global ocean carbon uptake through the solubility, physical and biological pumps. Many studies have estimated carbon export to the deep ocean, but very few have attempted a basin-scale perspective, or accounted for the sea-ice zone (SIZ). In this study, we use an extensive array of BGC-Argo floats to improve previous estimates of carbon export across basins and frontal zones, specifically including the SIZ. Using a new method involving changes in particulate organic carbon and dissolved oxygen along the mesopelagic layer, we find that the total Southern Ocean carbon export from 2014 to 2022 is 2.69 ± 1.23 PgC y⁻¹. The polar Antarctic zone contributes the most (41%) with 1.09 ± 0.46 PgC y⁻¹. Conversely, the SIZ contributes the least (8%) with 0.21 ± 0.09 PgC y⁻¹ and displays a strong shallow respiration in the upper 200 m. However, the SIZ contribution can increase up to 14% depending on the depth range investigated. We also consider vertical turbulent fluxes, which can be neglected at depth but are important near the surface. Our work provides a complementary approach to previous studies and is relevant for work that focuses on evaluating the biogeochemical impacts of changes in Antarctic sea-ice extent. Refining estimates of carbon export and understanding its drivers ultimately impacts our comprehension of climate variability at the global ocean scale.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008193","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143879904","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":"Ocean Carbon Export Flux Projections in CMIP6 Earth System Models Across Multiple Export Depth Horizons","authors":"Stevie L. Walker,&nbsp;Hilary I. Palevsky","doi":"10.1029/2024GB008329","DOIUrl":"https://doi.org/10.1029/2024GB008329","url":null,"abstract":"<p>The ocean's biological carbon pump (BCP) plays a key role in global carbon cycling by transporting biologically fixed carbon from the surface to the deep ocean. Prior analyses of the BCP in Earth System Model (ESM) simulations have typically evaluated particulate organic carbon (POC) flux at a fixed export depth horizon of 100 m. However, this overlooks spatial and temporal variations in the depth that sinking POC must penetrate to reach the mesopelagic or to sequester carbon from the atmosphere on climate-relevant timescales. We use depth-resolved POC flux output from eight Coupled Model Intercomparison Project Phase 6 (CMIP6) ESMs to compare global and regional changes in POC flux at five export depth horizons −100 m, the base of the euphotic zone (EZ depth), the particle compensation depth (PCD), the maximum annual mixed layer depth (MLD_max), and 1,000 m—under the high-emissions scenario SSP5-8.5. We also examine the relationship among net primary production, export efficiency from the surface ocean, and transfer efficiency to depth in key regions of the ocean, identifying model- and region-specific variations in the mechanistic drivers of POC flux changes in the deep ocean. Globally and spatially, trends in POC flux magnitude and decline are similar at the four surface export depth horizons, and multimodel variability in POC flux change by 2100 is greatest at the 1,000 m export depth horizon (+4% to −55%). This indicates the importance of improving model parameterizations of transfer efficiency and POC flux to the deep ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008329","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143849156","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":"Impacts of Permafrost Degradation on N2O Emissions From Natural Terrestrial Ecosystems in Northern High Latitudes: A Process-Based Biogeochemistry Model Analysis","authors":"Ye Yuan,&nbsp;Qianlai Zhuang,&nbsp;Bailu Zhao,&nbsp;Narasinha Shurpali","doi":"10.1029/2024GB008439","DOIUrl":"https://doi.org/10.1029/2024GB008439","url":null,"abstract":"<p>Nitrous oxide (N₂O) is a potent greenhouse gas with its radiative forcing 265–298 times stronger than that of carbon dioxide (CO₂). Recent field studies show N₂O emissions from northern high latitude (north of 45°N) ecosystems have increased due to warming. However, spatiotemporal quantification of N₂O emissions remains inadequate in this region. Here we revise the Terrestrial Ecosystem Model to incorporate more detailed processes of soil nitrogen (N) biogeochemical cycling, permafrost thawing effects, and atmospheric N deposition. Terrestrial Ecosystem Model is then used to analyze N₂O emissions from natural terrestrial ecosystems in the region. Our study reveals that regional N₂O production and net emissions increased from 1969 to 2019. Production rose from 1.12 (0.82–1.46) to 1.18 (0.84–1.51) Tg N yr⁻¹, while net emissions increased from 0.98 (0.7–1.34) to 1.05 (0.72–1.39) Tg N yr⁻¹, considering permafrost thawing. Emissions from permafrost regions grew from 0.37 (0.2–0.57) to 0.41 (0.21–0.6) Tg N yr⁻¹. Soil N₂O uptake from the atmosphere remained relatively stable at 0.12 (0.1–0.15) Tg N yr ⁻¹. Atmospheric N deposition significantly increased N₂O emission by 37.2 ± 2.9%. Spatially, natural terrestrial ecosystems act as net sources or sinks of −12 to 900 mg N m⁻² yr⁻¹ depending on changing temperature, precipitation, soil characteristics, and vegetation types. Our findings underscore the critical need for more observational studies to reduce the uncertainty in N₂O budget.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008439","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143845950","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":"Decoupling of N2O Production and Emissions in the Northern Indian Ocean","authors":"Yangyang Zhao,&nbsp;Laure Resplandy,&nbsp;Xianhui Sean Wan,&nbsp;Fan Yang,&nbsp;Enhui Liao,&nbsp;Bess Ward","doi":"10.1029/2024GB008481","DOIUrl":"https://doi.org/10.1029/2024GB008481","url":null,"abstract":"&lt;p&gt;The northern Indian Ocean is a hotspot of nitrous oxide (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O) emission to the atmosphere. Yet, the direct link between production and emission of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O in this region is still poorly constrained, in particular the relative contributions of denitrification, nitrification and ocean transport to the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O efflux. Here, we implemented a mechanistically based &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O cycling module into a regional ocean model of the Indian Ocean to examine how the biological production and transport of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O control the spatial variation of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O emissions in the basin. The model captures the upper ocean physical and biogeochemical dynamics of the northern Indian Ocean, including vertical and horizontal &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O distribution observed in situ and regionally integrated &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 ","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008481","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143840744","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":"South Asia's Ecosystems Are a Net Carbon Sink, But the Region Is a Major Net GHG Source to the Atmosphere","authors":"Atul K. Jain,&nbsp;Seetharaman Seshadri,&nbsp;Jatin Anand,&nbsp;Naveen Chandra,&nbsp;Prabir K. Patra,&nbsp;Josep G. Canadell,&nbsp;Abha Chhabra,&nbsp;Philippe Ciais,&nbsp;Hammad Gilani,&nbsp;Murali K. Gumma,&nbsp;Masayuki Kondo,&nbsp;Erandathie Lokupitiya,&nbsp;Naiqing Pan,&nbsp;Him Lal Shrestha,&nbsp;Baktiar N. Siddiqui,&nbsp;Hanqin Tian,&nbsp;Yogesh K. Tiwari","doi":"10.1029/2024GB008261","DOIUrl":"https://doi.org/10.1029/2024GB008261","url":null,"abstract":"<p>As part of the REgional Carbon Cycle Assessment and Processes-2 (RECCAP-2) project of the Global Carbon Project, here we estimate the GHG budgets (anthropogenic and natural sources and sinks) for the South Asia (SA) region as a whole and each country (Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka) for the decade of 2010–2019 (2010s). Countries in the region are experiencing a rapid rise in fossil fuel consumption and demand for agricultural land, leading to increased deforestation and higher greenhouse gas emissions. This study synthesizes top-down (TD) and bottom-up (BU) dynamic global vegetation model results, BU GHG inventories, ground-based observation upscaling, and direct emissions for major GHGs. The fluxes for carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) analyzed include fossil fuel emissions, net biome productivity, land use change, inland waters, wetlands, and upland and submerged soils. Our analysis shows that the overall total GHG emissions contributed to a net increase of 34%–43% during the 2010s compared to the 2000s, primarily driven by industrial activities. However, terrestrial ecosystems acted as a notable exception by serving as a CO₂ sink in the 2010s, effectively sequestering atmospheric carbon. The sink was significantly smaller than overall carbon emissions. Overall, the 2010s GHG emissions based on BU and TD were 4,517 ± 639.8 and 4,532 ± 807.5 Tg CO₂ eq, with CO₂, CH₄, and N₂O emissions of 2165.2 ± 297.1, 1,404 ± 95.9, and 712 ± 466 Tg CO₂ eq based on BU models 2,125 ± 515.1, 1,531 ± 205.2, and 876 ± 446.0 Tg CO₂ eq based on TD models. Total emissions from SA in the 2010s accounted for approximately 8% of the global share. The terrestrial CO₂ sinks estimated by the BU and TD models were 462.9 ± 195.5 and 210.0 ± 630.4 Tg CO₂, respectively. Among the SA countries, India was the largest emitter contributing to 80% of the region's total GHG emissions, followed by Pakistan (10%) and Bangladesh (7%).</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008261","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836241","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":"Centennial-Scale Storage of DOC Within Arctic Ocean Deep Waters Controlled by Subzero Temperatures","authors":"Robert T. Letscher,&nbsp;William M. Smethie,&nbsp;Dennis A. Hansell","doi":"10.1029/2024GB008428","DOIUrl":"https://doi.org/10.1029/2024GB008428","url":null,"abstract":"<p>Refractory dissolved organic carbon (RDOC) represents the second largest reservoir for ocean carbon storage, the bulk of which is held in the deep ocean, out of contact with the atmosphere on decadal to millennial timescales. Thus, understanding the mechanisms governing its production, delivery, and storage within the deep ocean is crucial for fully elucidating the oceanic carbon cycle and its impacts on global climate dynamics. Here we report observations of marine DOC across the Arctic, finding that the Eurasian Basin deep waters (&gt;1,700 m) harbor the global maxima in deep water DOC concentrations. Given the basin's relatively long residence time (&gt;150 years) and the absence of known RDOC delivery pathways into the ocean interior, we attempt to describe how the elevated Arctic Ocean deep water DOC is maintained. Using box model simulations, we find a significant role for brine rejection from continental shelf surface waters in delivering DOC to the abyss, which simultaneously ventilates Arctic Ocean deep waters. Comparison of kinetic loss rates for DOC consumption estimated as a function of subsurface temperatures demonstrates an elevated temperature sensitivity for Arctic RDOC relative to other ocean basins, possibly linked to its elevated terrigenous and/or “fresh” content, with the subzero temperatures of the Arctic currently suppressing DOC remineralization, helping to explain the deep water maxima. The Arctic Ocean currently stores ∼5.3 Pg C as DOC over the multi-centennial scale residence times of its deep waters, which may be reduced by ∼1%–4% over the next century of warming.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822172","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":"Differences in Sinking Processes and Biological Pump Contribution Among Phytoplankton Groups in the Mesopelagic Layer","authors":"T. Shimonaka,&nbsp;T. Kodama,&nbsp;S. Otosaka,&nbsp;J. Hirai,&nbsp;T. Wagawa,&nbsp;M. Nakae,&nbsp;K. Sakuma,&nbsp;K. Takahashi","doi":"10.1029/2024GB008476","DOIUrl":"https://doi.org/10.1029/2024GB008476","url":null,"abstract":"<p>The differing contributions of phytoplankton groups to biological pump have been insufficiently explored. We evaluated the sinking of phytoplankton in the mesopelagic layer using 16S rRNA gene amplicon sequencing. Sinking particles were collected from June to August 2022 in the Sea of Japan using sediment traps moored at depths of 387 and 890 m. Morphologically categorized fecal pellets—ellipsoidal, cylindrical, spherical, and tabular types—were analyzed for their carbon content and phytoplankton assemblages as well as the bulk and non-fecal particles. Fecal pellets contributed ≤4.1% and ≤8.0% of the total particulate organic carbon (POC) flux at 387 and 890 m depths, respectively. Ellipsoidal pellets, likely of appendicularian origin, accounted for 59.3%–78.5% of the fecal pellets' carbon fluxes. Diatoms, particularly Chaetocerotales, were the dominant phytoplankton group across all sinking types and depths, as indicated by eukaryotic chloroplast and cyanobacteria gene proportions. Cyanobacteria Synechococcales were most prevalent in ellipsoidal and cylindrical fecal pellets at 890 m depth. Amplicon sequence variant richness positively correlated with fecal pellet's POC content, with Synechococcales and Chaetocerotales exhibiting the highest diversity in ellipsoidal fecal pellets at both depths. Non-Chaetocerotales diatoms showed comparable or lower diversity levels than the non-fecal particles. These findings suggest that Chaetocerotales and Synechococcales were the most effectively transported phytoplankton groups into the mesopelagic layer through zooplankton grazing and repackaging, particularly by appendicularians. In contrast, other phytoplankton groups, including non-Chaetocerotales diatoms, played a less significant role in this process.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008476","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818622","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":"Widespread Black Carbon Deposition of Varied Origin Exported From Glaciers","authors":"Amy D. Holt,&nbsp;Riley Barton,&nbsp;Sasha Wagner,&nbsp;Amy M. McKenna,&nbsp;Jason Fellman,&nbsp;Eran Hood,&nbsp;Tom I. Battin,&nbsp;Hannes Peter,&nbsp;Vanishing Glaciers Field Team,&nbsp;Robert G. M. Spencer","doi":"10.1029/2024GB008359","DOIUrl":"https://doi.org/10.1029/2024GB008359","url":null,"abstract":"<p>Atmospheric deposition delivers carbon to glacier surfaces, including from fossil fuel and biomass combustion. Nonetheless, spatial variation in the sources of organic and black carbon deposited on glaciers is poorly understood, along with their role in driving glacier outflow dissolved organic matter (DOM) composition and fate. Here, we used bulk and compound-specific carbon isotopic analyses to constrain the sources of dissolved organic carbon (DOC) and dissolved black carbon (DBC) in 10 glacier outflows across four regions. To understand the relationships between glacier DOM composition and sources of DOC and DBC, isotopic data were used in conjunction with ultrahigh resolution molecular-level analyses. Globally, a substantial yet variable component of DOC was sourced from anthropogenic aerosols (12%–91%; median 50%), influencing regional DOM composition (aliphatics 26.9%–58.4% relative abundance; RA). Relatively older radiocarbon ages (i.e., larger fossil-derived component) of glacier DOC were correlated with more ¹³C depleted DOC and DBC signatures, where DOM had higher aromaticity, elevated RA of condensed aromatics, and a lower RA of aliphatic compounds. This study highlights that anthropogenic deposition is pervasive, but its extent varies spatially with ramifications for DOM composition, and thus reactivity and fate.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143801545","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":"Multi-Elemental Tracers in the Amerasian Basin Reveal Interlinked Biogeochemical and Physical Processes in the Arctic Ocean Upper Halocline","authors":"L. M. Whitmore,&nbsp;L. Jensen,&nbsp;J. Granger,&nbsp;Y. Xiang,&nbsp;L. Kipp,&nbsp;A. Pasqualini,&nbsp;R. Newton,&nbsp;A. M. Agather,&nbsp;R. F. Anderson,&nbsp;E. E. Black,&nbsp;K. L. Bowman,&nbsp;A. Bourbonnais,&nbsp;M. A. Brzezinski,&nbsp;R. M. Bundy,&nbsp;M. A. Charette,&nbsp;R. L. Edwards,&nbsp;J. N. Fitzsimmons,&nbsp;D. A. Hansell,&nbsp;P. J. Lam,&nbsp;P. Morton,&nbsp;M. A. Saito,&nbsp;P. Schlosser,&nbsp;A. M. Shiller,&nbsp;W. M. Smethie,&nbsp;B. S. Twining,&nbsp;R. J. Woosley,&nbsp;R. Zhang","doi":"10.1029/2024GB008342","DOIUrl":"https://doi.org/10.1029/2024GB008342","url":null,"abstract":"<p>The physical and biogeochemical properties of the western Arctic Ocean are rapidly changing, resulting in cascading shifts to the local ecosystems. The nutrient-rich Pacific water inflow to the Arctic through the Bering Strait is modified on the Chukchi and East Siberian shelves by brine rejection during sea ice formation, resulting in a strong halocline (called the Upper Halocline Layer (UHL)) that separates the cold and relatively fresh surface layer from the warmer and more saline (and nutrient-poor) Atlantic-derived water below. Biogeochemical signals entrained into the UHL result from Pacific Waters modified by sediment and river influence on the shelf. In this synthesis, we bring together data from the 2015 Arctic U.S. GEOTRACES program to implement a multi-tracer (dissolved and particulate trace elements, radioactive and stable isotopes, macronutrients, and dissolved gas/atmospheric tracers) approach to assess the relative influence of shelf sediments, rivers, and Pacific seawater contribution to the Amerasian Arctic halocline. For each element, we characterized their behavior as mixing dominated (e.g., dCu, dGa), shelf-influenced (e.g., dFe, dZn), or a combination of both (e.g., dBa, dNi). Leveraging this framework, we assessed sources and sinks contributing to elemental distributions: shelf sediments (e.g., dFe, dZn, dCd, dHg), riverine sources, (e.g., dCu, dBa, dissolved organic carbon), and scavenging by particles originating on the shelf (e.g., dFe, dMn, dV, etc.). Additionally, synthesized results from isotopic and atmospheric tracers yielded tracer age estimates for the Upper Halocline ranging between 1 and 2 decades on a spatial gradient consistent with cyclonic circulation.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008342","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143793519","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}