Global Biogeochemical Cycles最新文献

{"title":"The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling","authors":"Justine Ramage,&nbsp;McKenzie Kuhn,&nbsp;Anna-Maria Virkkala,&nbsp;Carolina Voigt,&nbsp;Maija E. Marushchak,&nbsp;Ana Bastos,&nbsp;Christina Biasi,&nbsp;Josep G. Canadell,&nbsp;Philippe Ciais,&nbsp;Efrèn López-Blanco,&nbsp;Susan M. Natali,&nbsp;David Olefeldt,&nbsp;Stefano Potter,&nbsp;Benjamin Poulter,&nbsp;Brendan M. Rogers,&nbsp;Edward A. G. Schuur,&nbsp;Claire Treat,&nbsp;Merritt R. Turetsky,&nbsp;Jennifer Watts,&nbsp;Gustaf Hugelius","doi":"10.1029/2023GB007953","DOIUrl":"https://doi.org/10.1029/2023GB007953","url":null,"abstract":"<p>The northern permafrost region has been projected to shift from a net sink to a net source of carbon under global warming. However, estimates of the contemporary net greenhouse gas (GHG) balance and budgets of the permafrost region remain highly uncertain. Here, we construct the first comprehensive bottom-up budgets of CO₂, CH₄, and N₂O across the terrestrial permafrost region using databases of more than 1000 in situ flux measurements and a land cover-based ecosystem flux upscaling approach for the period 2000–2020. Estimates indicate that the permafrost region emitted a mean annual flux of 12 (−606, 661) Tg CO₂–C yr⁻¹, 38 (22, 53) Tg CH₄–C yr⁻¹, and 0.67 (0.07, 1.3) Tg N₂O–N yr⁻¹ to the atmosphere throughout the period. Thus, the region was a net source of CH₄ and N₂O, while the CO₂ balance was near neutral within its large uncertainties. Undisturbed terrestrial ecosystems had a CO₂ sink of −340 (−836, 156) Tg CO₂–C yr⁻¹. Vertical emissions from fire disturbances and inland waters largely offset the sink in vegetated ecosystems. When including lateral fluxes for a complete GHG budget, the permafrost region was a net source of C and N, releasing 144 (−506, 826) Tg C yr⁻¹ and 3 (2, 5) Tg N yr⁻¹. Large uncertainty ranges in these estimates point to a need for further expansion of monitoring networks, continued data synthesis efforts, and better integration of field observations, remote sensing data, and ecosystem models to constrain the contemporary net GHG budgets of the permafrost region and track their future trajectory.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007953","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345761","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":"Relationships Between Plankton Size Spectra, Net Primary Production, and the Biological Carbon Pump","authors":"Michael R. Stukel,&nbsp;Moira Décima,&nbsp;Thomas B. Kelly,&nbsp;Michael R. Landry,&nbsp;Scott D. Nodder,&nbsp;Mark D. Ohman,&nbsp;Karen E. Selph,&nbsp;Natalia Yingling","doi":"10.1029/2023GB007994","DOIUrl":"https://doi.org/10.1029/2023GB007994","url":null,"abstract":"<p>Photosynthesis in the surface ocean and subsequent export of a fraction of this fixed carbon leads to carbon dioxide sequestration in the deep ocean. Ecological relationships among plankton functional groups and theoretical relationships between particle size and sinking rate suggest that carbon export from the euphotic zone is more efficient when communities are dominated by large organisms. However, this hypothesis has never been tested against measured size spectra spanning the &gt;5 orders of magnitude found in plankton communities. Using data from five ocean regions (California Current Ecosystem, North Pacific subtropical gyre, Costa Rica Dome, Gulf of Mexico, and Southern Ocean subtropical front), we quantified carbon-based plankton size spectra from heterotrophic bacteria to metazoan zooplankton (size class cutoffs varied slightly between regions) and their relationship to net primary production and sinking particle flux. Slopes of the normalized biomass size spectra (NBSS) varied from −1.6 to −1.2 (median slope of −1.4 equates to large 1–10 mm organisms having a biomass equal to only 7.6% of the biomass in small 1–10 μm organisms). Net primary production was positively correlated with the NBSS slope, with a particularly strong relationship in the microbial portion of the size spectra. While organic carbon export co-varied with NBSS slope, we found only weak evidence that export efficiency is related to plankton community size spectra. Multi-variate statistical analysis suggested that properties of the NBSS added no explanatory power over chlorophyll, primary production, and temperature. Rather, the results suggest that both plankton size spectra and carbon export increase with increasing system productivity.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140333213","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":"Nitrogen Cycling Feedback on Carbon Dynamics Leads to Greater CH4 Emissions and Weaker Cooling Effect of Northern Peatlands","authors":"Bailu Zhao,&nbsp;Qianlai Zhuang","doi":"10.1029/2023GB007978","DOIUrl":"https://doi.org/10.1029/2023GB007978","url":null,"abstract":"<p>Northern peatlands have been a carbon sink since their initiation. This has been simulated by existing process-based models. However, most of these models are limited by lacking sufficient processes of the N cycle in peatlands. Here, we use a peatland biogeochemistry model incorporated with N-related processes of fixation, deposition, gas emission, loss through water flow, net mineralization, plant uptake and litterfall to project the role of the peatlands in future radiative forcing (RF). Simulations from 15-ka BP to 2100 are conducted driven by CMIP5 climate forcing data of IPSL-CM5A-LR and bcc-csm1-1, including warming scenarios of RCP 2.6, RCP 4.5 and RCP 8.5. During the Holocene, northern peatlands have an increasing cooling effect with RF up to −0.57 W m⁻². By 1990, these peatlands accumulate 408 Pg C and 7.8 Pg N. Under warming, increasing mineral N content enhances plant net primary productivity; the cooling effect persists. However, RF increases by 0.1–0.5 W m⁻² during the 21st century, mainly due to the stimulated CH₄ emissions. Northern peatlands could switch from a C sink to a source when the annual temperature exceeds −2.2 to −0.5°C. This study highlights that the improved N cycle causes higher CO₂-C sink capacity in northern peatlands. However, it also causes a significant increase in CH₄ emissions, which weakens the cooling effect of northern peatlands in future climate.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007978","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297279","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 Importance of Riverine Nutrient Supply for the Marine Silica Pump of Arctic Shelves: Evidence From the Laptev Sea","authors":"M. C. F. Debyser,&nbsp;L. Pichevin,&nbsp;R. E. Tuerena,&nbsp;A. Doncila,&nbsp;I. Semiletov,&nbsp;R. S. Ganeshram","doi":"10.1029/2023GB007828","DOIUrl":"https://doi.org/10.1029/2023GB007828","url":null,"abstract":"<p>Arctic shelves receive a large load of nutrients from Arctic rivers, which play a major role in the biogeochemical cycles of the Arctic Ocean. In this study, we present measurements of dissolved silicon isotopes (δ³⁰Si(OH)₄) around the Laptev Sea and surface waters of the Eurasian shelves collected in October 2018 to document terrestrial silicon modifications on shelves and their contribution to the Arctic basin. Nitrogen was found to be depleted in surface waters and the limiting nutrient to primary production in the Laptev Sea, allowing excess silicon export to the central Arctic Ocean. Heavy δ³⁰Si(OH)₄ in the water column was linked to the strong biological removal of DSi on shelves, enabled by vigorous N recycling. From isotopically constrained processes, we estimate that &gt;50% of the silicon from riverine inputs is removed within the Lena River delta and on the Laptev Sea shelf. Extrapolating this to major Siberian rivers, this leads to an export of 2.5 ± 0.8 kmol/s of riverine silicon through the Transpolar Drift. An updated isotopic budget of the Arctic Ocean reproduces the observed δ³⁰Si(OH)₄ signatures out of the Arctic Ocean and underlines the importance of biological processes in modulating silicon export. Given that opal burial fluxes on Artic shelves are controlled by denitrification and N-limitation, these processes are sensitive to ongoing climate change. As a consequence of higher riverine DSi inputs and shelf denitrification responding to productivity, it is inferred that silicon export from the Arctic Ocean could increase in the future, accompanied by lighter δ³⁰Si(OH)₄ signatures.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007828","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297242","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":"Characterizing the Atmospheric Mn Cycle and Its Impact on Terrestrial Biogeochemistry","authors":"Louis Lu,&nbsp;Longlei Li,&nbsp;Sagar Rathod,&nbsp;Peter Hess,&nbsp;Carmen Martínez,&nbsp;Nicole Fernandez,&nbsp;Christine Goodale,&nbsp;Janice Thies,&nbsp;Michelle Y. Wong,&nbsp;Maria Grazia Alaimo,&nbsp;Paulo Artaxo,&nbsp;Francisco Barraza,&nbsp;Africa Barreto,&nbsp;David Beddows,&nbsp;Shankarararman Chellam,&nbsp;Ying Chen,&nbsp;Patrick Chuang,&nbsp;David D. Cohen,&nbsp;Gaetano Dongarrà,&nbsp;Cassandra Gaston,&nbsp;Darío Gómez,&nbsp;Yasser Morera-Gómez,&nbsp;Hannele Hakola,&nbsp;Jenny Hand,&nbsp;Roy Harrison,&nbsp;Philip Hopke,&nbsp;Christoph Hueglin,&nbsp;Yuan-Wen Kuang,&nbsp;Katriina Kyllönen,&nbsp;Fabrice Lambert,&nbsp;Willy Maenhaut,&nbsp;Randall Martin,&nbsp;Adina Paytan,&nbsp;Joseph Prospero,&nbsp;Yenny González,&nbsp;Sergio Rodriguez,&nbsp;Patricia Smichowski,&nbsp;Daniela Varrica,&nbsp;Brenna Walsh,&nbsp;Crystal Weagle,&nbsp;Yi-Hua Xiao,&nbsp;Natalie Mahowald","doi":"10.1029/2023GB007967","DOIUrl":"https://doi.org/10.1029/2023GB007967","url":null,"abstract":"<p>The role of manganese (Mn) in ecosystem carbon (C) biogeochemical cycling is gaining increasing attention. While soil Mn is mainly derived from bedrock, atmospheric deposition could be a major source of Mn to surface soils, with implications for soil C cycling. However, quantification of the atmospheric Mn cycle, which comprises emissions from natural (desert dust, sea salts, volcanoes, primary biogenic particles, and wildfires) and anthropogenic sources (e.g., industrialization and land-use change due to agriculture), transport, and deposition, remains uncertain. Here, we use compiled emission data sets for each identified source to model and quantify the atmospheric Mn cycle by combining an atmospheric model and in situ atmospheric concentration measurements. We estimated global emissions of atmospheric Mn in aerosols (&lt;10 μm in aerodynamic diameter) to be 1,400 Gg Mn year⁻¹. Approximately 31% of the emissions come from anthropogenic sources. Deposition of the anthropogenic Mn shortened Mn “pseudo” turnover times in 1-m-thick surface soils (ranging from 1,000 to over 10,000,000 years) by 1–2 orders of magnitude in industrialized regions. Such anthropogenic Mn inputs boosted the Mn-to-N ratio of the atmospheric deposition in non-desert dominated regions (between 5 × 10⁻⁵ and 0.02) across industrialized areas, but that was still lower than soil Mn-to-N ratio by 1–3 orders of magnitude. Correlation analysis revealed a negative relationship between Mn deposition and topsoil C density across temperate and (sub)tropical forests, consisting with atmospheric Mn deposition enhancing carbon respiration as seen in in situ biogeochemical studies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007967","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140310320","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":"Overwinter and Spring Thaw Nitrous Oxide Fluxes in a Northern Prairie Cropland Are Limited but a Significant Proportion of Annual Emissions","authors":"Claudia Wagner-Riddle,&nbsp;Kate A. Congreves,&nbsp;Shannon E. Brown,&nbsp;Warren D. Helgason,&nbsp;Richard E. Farrell","doi":"10.1029/2023GB008051","DOIUrl":"https://doi.org/10.1029/2023GB008051","url":null,"abstract":"<p>Croplands that experience seasonal soil freezing and thawing have been shown to be significant sources of N₂O emissions. Yet, there is a paucity of year-round N₂O emission data for one of the most significant crop production regions that seasonally freeze, the Prairies. Here, we present micrometeorological N₂O fluxes measured over 4 years in Saskatchewan, Canada, to evaluate the magnitude of freeze-thaw N₂O emissions and investigate its driving factors. Significant thaw related emissions occurred in 2 of the 4 years and were associated with relatively higher fall nitrate levels and a more gradual soil thawing period. Overall, fall soil nitrate levels were a strong explanatory variable for the differences in non-growing season (NGS) N₂O emission (<i>r</i>² = 0.485). Measured cumulative N₂O emissions for the NGS were 123–938 g N ha⁻¹ and were much smaller than those obtained at other cold climate sites but amounted to 52% of annual totals on average. The November to April period contributed 30% of the annual total emissions in years without major thaw events, but 70% in years with significant thaws. NGS N₂O emissions were not explained by cumulative freezing degree days unlike most other cold climate sites. We propose that NGS N₂O emissions are more strongly influenced by thaw dynamics during freezing-thawing conditions in dry regions, whereas freezing intensity is the dominant factor for wetter regions. Our results indicate that even for a semi-arid region freeze-thaw is an important source of N₂O emissions and must be considered for more accurate reporting and development of mitigation strategies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297241","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":"Mycorrhizal Types Modulate Responses of Global Soil Microbial Biomass to Environments Across Varied Land Use Types","authors":"Mingli Yuan,&nbsp;Zhaoyong Shi,&nbsp;Fayuan Wang,&nbsp;Menghan Zhang,&nbsp;Shuang Yang","doi":"10.1029/2023GB008044","DOIUrl":"https://doi.org/10.1029/2023GB008044","url":null,"abstract":"<p>Soil microbial biomass (SMB) is a fundamental contributor to soil ecosystem services. Mycorrhizal fungi, a significant group of soil microbes, play essential roles in regulating carbon allocation and nutrient cycles. Acknowledging the profound importance of SMB and mycorrhizal symbiosis, our objective was to explore how mycorrhizal types modulate the global patterns of SMB across varied land use types (LUTs). Using data from 329 independent studies, we categorized vegetation species with defined mycorrhizal types into arbuscular mycorrhizal (AM) type (with 958 observations) or mixed AM and ectomycorrhizal (AM + ECM) type (with 481 observations). This categorization served as the foundation for our investigation into the impacts of various LUTs and environmental conditions (mean annual temperature, and mean annual precipitation, MAP) on global SMB patterns associated with specific mycorrhizal associations. The overall mean value of SMB was remarkably higher under AM + ECM type (92.23 ± 4.73 nmol/g) compared with that under AM type (49.45 ± 1.87 nmol/g) at a global scale. The primary factor contributing to this difference was the natural system. Additionally, the AM + ECM type (0.19 ± 0.01) exhibited a higher F:B ratio (Fungi-to-bacteria ratio) than the AM type (0.16 ± 0.001), attributed to the cumulative effects of different LUTs. Furthermore, SMB was markedly positively affected by aridity index under AM type and negatively influenced by temperature under AM + ECM type. Besides, MAP had a pronounced positive impact on SMB under AM type, while exhibiting a negative impact under AM + ECM type. Our study presented evidence affirming the essential role of mycorrhizal associations in shaping global patterns of SMB in response to environmental factors across varied LUTs.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 3","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140209638","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":"Mechanisms Underpinning the Net Removal Rates of Dissolved Organic Carbon in the Global Ocean","authors":"Sinikka T. Lennartz,&nbsp;David P. Keller,&nbsp;Andreas Oschlies,&nbsp;Bernd Blasius,&nbsp;Thorsten Dittmar","doi":"10.1029/2023GB007912","DOIUrl":"https://doi.org/10.1029/2023GB007912","url":null,"abstract":"<p>With almost 700 Pg of carbon, marine dissolved organic carbon (DOC) stores more carbon than all living biomass on Earth combined. However, the controls behind the persistence and the spatial patterns of DOC concentrations on the basin scale remain largely unknown, precluding quantitative assessments of the fate of this large carbon pool in a changing climate. Net removal rates of DOC along the overturning circulation suggest lifetimes of millennia. These net removal rates are in stark contrast to the turnover times of days to weeks of heterotrophic microorganisms, which are the main consumers of organic carbon in the ocean. Here, we present a dynamic “MICrobial DOC” model (MICDOC) with an explicit representation of picoheterotrophs to test whether ecological mechanisms may lead to observed decadal to millennial net removal rates. MICDOC is in line with &gt;40,000 DOC observations. Contrary to other global models, the reactivity of DOC fractions is not prescribed, but emerges from a dynamic feedback between microbes and DOC governed by carbon and macronutrient availability. A colimitation of macronutrients and organic carbon on microbial DOC uptake explains &gt;70% of the global variation of DOC concentrations, and governs characteristic features of its distribution. Here, decadal to millennial net removal rates emerge from microbial processes acting on time scales of days to weeks, suggesting that the temporal variability of the marine DOC inventory may be larger than previously thought. With MICDOC, we provide a foundation for assessing global effects on DOC related to changes in heterotrophic microbial communities in a future ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 3","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007912","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140192263","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":"Controls on Polar Southern Ocean Deep Chlorophyll Maxima: Viewpoints From Multiple Observational Platforms","authors":"Philip W. Boyd,&nbsp;David Antoine,&nbsp;Kimberley Baldry,&nbsp;Marin Cornec,&nbsp;Michael Ellwood,&nbsp;Svenja Halfter,&nbsp;Leo Lacour,&nbsp;Pauline Latour,&nbsp;Robert F. Strzepek,&nbsp;Thomas W. Trull,&nbsp;Tyler Rohr","doi":"10.1029/2023GB008033","DOIUrl":"https://doi.org/10.1029/2023GB008033","url":null,"abstract":"<p>Deep Chlorophyll Maxima (DCMs) are ubiquitous in low-latitude oceans, and of recognized biogeochemical and ecological importance. DCMs have been observed in the Southern Ocean, initially from ships and recently from profiling robotic floats, but with less understanding of their onset, duration, underlying drivers, or whether they are associated with enhanced biomass features. We report the characteristics of a DCM and a Deep Biomass Maximum (DBM) in the Inter-Polar-Frontal-Zone (IPFZ) south of Australia derived from CTD profiles, shipboard-incubated samples, a towbody, and a BGC-ARGO float. The DCM and DBM were ∼20 m thick and co-located with the nutricline, in the vicinity of a subsurface ammonium maximum characteristic of the IPFZ, but ∼100 m shallower than the ferricline. Towbody transects demonstrated that the co-located DCM/DBM was broadly present across the IPFZ. Large healthy diatoms, with low iron requirements, resided within the DCM/DBM, and fixed up to 20 mmol C m⁻² d⁻¹. The BGC-ARGO float revealed that DCM/DBM persisted for &gt;3 months. We propose a dual environmental mechanism to drive DCM/DBM formation and persistence within the IPFZ: sustained supply of both recycled iron within the subsurface ammonium maxima, and upward silicate transport from depth. DCM/DBM cell-specific growth rates were considerably slower than those in the overlying mixed layer, implying that phytoplankton losses such as herbivory are also reduced, possibly because of heavily silicified diatom frustules. The light-limited seasonal termination of the observed DCM/DBM did not result in a “diatom dump”, rather ongoing diatom downward export occurred throughout its multi-month persistence.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 3","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008033","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140192264","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":"Mechanistic Constraints on the Drivers of Southern Ocean Meridional Iron Distributions Between Tasmania and Antarctica","authors":"Christopher D. Traill,&nbsp;Paula Conde-Pardo,&nbsp;Tyler Rohr,&nbsp;Pier van der Merwe,&nbsp;Ashley T. Townsend,&nbsp;Pauline Latour,&nbsp;Melanie Gault-Ringold,&nbsp;Kathrin Wuttig,&nbsp;Matthew Corkill,&nbsp;Thomas M. Holmes,&nbsp;Mark J. Warner,&nbsp;Elizabeth Shadwick,&nbsp;Andrew R. Bowie","doi":"10.1029/2023GB007856","DOIUrl":"https://doi.org/10.1029/2023GB007856","url":null,"abstract":"<p>While modeling efforts have furthered our understanding of marine iron biogeochemistry and its influence on carbon sequestration, observations of dissolved iron (dFe) and its relationship to physical, chemical and biological processes in the ocean are needed to both validate and inform model parameterization. Where iron comes from, how it is transported and recycled, and where iron removal takes place are critical mechanisms that need to be understood to assess the relationship between iron availability and primary production. To this end, hydrographic and trace metal observations across the GO-SHIP section SR3, south of Tasmania, Australia, have been analyzed in tandem with the novel application of an optimum multiparameter analysis. From the trace-metal distribution south of Australia, key differences in the drivers of dFe between oceanographic zones of the Southern Ocean were identified. In the subtropical zone, sources of dFe were attributed to waters advected off the continental shelf, and to recirculated modified mode and intermediate water-masses of the Tasman Outflow. In the subantarctic zone, the seasonal replenishment of dFe in Antarctic surface and mode waters appears to be sustained by iron recycling in the underlying mode and intermediate waters. In the southern zone, the dFe distribution is likely driven by dissolution and scavenging by high concentrations of particles along the Antarctic continental shelf and slope entrained in high salinity shelf water. This approach to trace metal analysis may prove useful in future transects for identifying key mechanisms driving marine dissolved trace metal distributions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 3","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007856","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140181619","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}