Global Biogeochemical Cycles最新文献

{"title":"Dissolved Organic Carbon in Coastal Waters: Global Patterns, Stocks and Environmental Physical Controls","authors":"Christian Lønborg,&nbsp;Isabel Fuentes-Santos,&nbsp;Cátia Carreira,&nbsp;Valentina Amaral,&nbsp;Javier Arístegui,&nbsp;Punyasloke Bhadury,&nbsp;Mariana Bernardi Bif,&nbsp;Maria Ll. Calleja,&nbsp;Qi Chen,&nbsp;Luiz C. Cotovicz Jr.,&nbsp;Stefano Cozzi,&nbsp;Bradley D. Eyre,&nbsp;E. Elena García-Martín,&nbsp;Michele Giani,&nbsp;Rafael Gonçalves-Araujo,&nbsp;Renee Gruber,&nbsp;Dennis A. Hansell,&nbsp;Johnna M. Holding,&nbsp;William Hunter,&nbsp;J. Severino P. Ibánhez,&nbsp;Valeria Ibello,&nbsp;Piotr Kowalczuk,&nbsp;Federica Maggioni,&nbsp;Paolo Magni,&nbsp;Patrick Martin,&nbsp;S. Leigh McCallister,&nbsp;Xosé Anxelu G. Morán,&nbsp;Joanne M. Oakes,&nbsp;Helena Osterholz,&nbsp;Hyekyung Park,&nbsp;Digna Rueda-Roa,&nbsp;Jiang Shan,&nbsp;Eva Teira,&nbsp;Nicholas Ward,&nbsp;Youhei Yamashita,&nbsp;Liyang Yang,&nbsp;Qiang Zheng,&nbsp;Xosé Antón Álvarez-Salgado","doi":"10.1029/2024GB008407","DOIUrl":"https://doi.org/10.1029/2024GB008407","url":null,"abstract":"<p>Dissolved organic carbon (DOC) in coastal waters is integral to biogeochemical cycling, but global and regional drivers of DOC are still uncertain. In this study we explored spatial and temporal differences in DOC concentrations and stocks across the global coastal ocean, and how these relate to temperature and salinity. We estimated a global median coastal DOC stock of 3.15 Pg C (interquartile range (IQR) = 0.85 Pg C), with median DOC concentrations being 2.2 times higher than in open ocean surface waters. Globally and seasonally, salinity was the main driver of DOC with concentrations correlated negatively with salinity, without a clear relationship to temperature. DOC concentrations and stocks varied with region and season and this pattern is likely driven by riverine inputs of DOC and nutrients that stimulate coastal phytoplankton production. Temporally, high DOC concentrations occurred mainly in months with high freshwater input, with some exceptions such as in Eastern Boundary Current margins where peaks are related to primary production stimulated by nutrients upwelled from the adjacent ocean. No spatial trend between DOC and temperature was apparent, but many regions (19 out of 25) had aligned peaks of seasonal temperature and DOC, related to increased phytoplankton production and vertical stratification at high temperatures. Links of coastal DOC with salinity and temperature highlight the potential for anthropogenic impacts to alter coastal DOC concentration and composition, and thereby ecosystem status.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008407","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143900965","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":"Offset Between Profiling Float and Shipboard Oxygen Observations at Depth Imparts Bias on Float pH and Derived pCO2","authors":"Seth M. Bushinsky,&nbsp;Zachary Nachod,&nbsp;Andrea J. Fassbender,&nbsp;Veronica Tamsitt,&nbsp;Yuichiro Takeshita,&nbsp;Nancy Williams","doi":"10.1029/2024GB008185","DOIUrl":"https://doi.org/10.1029/2024GB008185","url":null,"abstract":"<p>Profiles of oxygen measurements from Argo profiling floats now vastly outnumber shipboard profiles. To correct for drift, float oxygen data are often initially adjusted to deployment casts, ship-based climatologies, or, recently, measurements of atmospheric oxygen for in situ calibration. Air calibration enables accurate measurements in the upper ocean but may not provide similar accuracy at depth. Using a quality controlled shipboard data set, we find that the entire Argo oxygen data set is offset relative to shipboard measurements (float minus ship) at pressures of 1,450–2,000 db by a median of −1.9 μmol kg⁻¹ (mean ± SD of −1.9 ± 3.9, 95% confidence interval around the mean of {−2.2, −1.6}) and air-calibrated floats are offset by −2.7 μmol kg⁻¹ (−3.0 ± 3.4 (CI_95%{−3.7, −2.4}). The difference between float and shipboard oxygen is likely due to offsets in the float oxygen data and not oxygen changes at depth or biases in the shipboard data set. In addition to complicating the calculation of long-term ocean oxygen changes, these float oxygen offsets impact the adjustment of float nitrate and pH measurements, therefore biasing important derived quantities such as the partial pressure of CO₂ (<i>p</i>CO₂) and dissolved inorganic carbon. Correcting floats with air-calibrated oxygen sensors for the float-ship oxygen offsets alters float pH by a median of 3.0 mpH (3.1 ± 3.7) and float-derived surface <i>p</i>CO₂ by −3.2 μatm (−3.2 ± 3.9). This adjustment to float <i>p</i>CO₂ represents half, or more, of the bias in float-derived <i>p</i>CO₂ reported in studies comparing float <i>p</i>CO₂ to shipboard <i>p</i>CO₂ measurements.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143901070","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":"Glacial-Interglacial and Millennial-Scale Changes in Nitrous Oxide Emissions Pathways and Source Regions","authors":"J. A. Menking,&nbsp;J. E. Lee,&nbsp;E. J. Brook,&nbsp;J. Schmitt,&nbsp;L. Soussaintjean,&nbsp;H. Fischer,&nbsp;J. Kaiser,&nbsp;A. Rice","doi":"10.1029/2024GB008287","DOIUrl":"https://doi.org/10.1029/2024GB008287","url":null,"abstract":"<p>During the transition from the Last Glacial Maximum (LGM) to the Holocene, the atmospheric N₂O mole fraction increased by 80 nmol mol⁻¹. Using ice core measurements of N₂O isotopomer ratios, we show that this increase was driven by increases in both nitrification and denitrification, with the relative partitioning between both production pathways depending on the assumed isotopic end-member source signatures. Similarly, we also attribute a 35 nmol mol⁻¹ N₂O mole fraction increase during the Heinrich Stadial 4/Dansgaard Oeschger 8 (HS4/DO8) millennial-scale event to increases in both N₂O production pathways. In contrast, the 25 nmol mol⁻¹ N₂O mole fraction decrease during the Younger Dryas was driven almost exclusively by a decrease in nitrification. The deglacial and HS4/DO8 increases in N₂O production occurred in both marine and terrestrial environments, with the terrestrial source responding faster to warming by about two centuries. Constraints on <i>changes</i> in nitrification and denitrification emissions are robust and consistent with previous studies showing the sensitivity of N₂O emissions to abrupt Northern Hemisphere warming. This study demonstrates for the first time the importance of both denitrification and nitrification pathways in driving source changes. Absolute emissions are more uncertain due to uncertainty about source isotopomer signatures. For instance, the contribution of denitrification to emissions at the LGM shifts from (65 ± 10) % to (91 ± 6) % when factoring in isotope enrichment due to partial reduction of N₂O to N₂ during denitrification. Reducing uncertainty in source signatures will increase the power of ice core N₂O isotope records in deducing environmental change.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008287","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143901009","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":"CO2 Uptake in the Pacific From 1985 to 2018: A Comparative Assessment of Observation- and Model-Based Estimates","authors":"Masao Ishii,&nbsp;Brendan R. Carter,&nbsp;Katsuya Toyama,&nbsp;Keith B. Rodgers,&nbsp;Richard A. Feely,&nbsp;Thi-Tuyet-Trang Chau,&nbsp;Frédéric Chevallier,&nbsp;Flora Desmet,&nbsp;Luke Gregor,&nbsp;Yosuke Iida,&nbsp;Yoshiteru Kitamura,&nbsp;Jens Daniel Müller,&nbsp;Hiroyuki Tsujino","doi":"10.1029/2024GB008355","DOIUrl":"https://doi.org/10.1029/2024GB008355","url":null,"abstract":"<p>As a contribution to the second REgional Carbon Cycle Assessment and Processes effort, we compare net and anthropogenic sea-air CO₂ fluxes, CO₂ accumulation rates in the ocean interior and their trends in the Pacific Ocean by analyzing results from state-of-the-art observation-based estimates and global ocean biogeochemistry models (GOBMs) over the period 1985–2018. The ensemble-mean net CO₂ fluxes integrated over the Pacific (44°S–62°N) are −0.41 ± 0.12 PgC yr⁻¹ from <i>p</i>CO₂ products and −0.51 ± 0.16 PgC yr⁻¹ from GOBMs. The anthropogenic CO₂ flux from GOBMs (−0.71 ± 0.10 PgC yr⁻¹) is 1.4 times as large as the net CO₂ flux, with particularly large anthropogenic uptake in the equatorial region (−0.34 ± 0.03 PgC yr⁻¹) significantly offsetting the large natural CO₂ outgassing there (+0.72 ± 0.06 PgC yr⁻¹). The basin-wide net CO₂ uptake has increased at similar mean rates of −0.09 ± 0.06 and −0.08 ± 0.02 PgC yr⁻¹ decade⁻¹ in <i>p</i>CO₂ products and GOBMs, respectively, comparable with the increase in anthropogenic CO₂ uptake of −0.10 ± 0.01 PgC yr⁻¹ decade⁻¹ in GOBMs. However, a notable mismatch in the trend of the net CO₂ flux change that exists between <i>p</i>CO₂ products (+0.00 ± 0.02 PgC yr⁻¹ decade⁻¹) and GOBMs (−0.04 ± 0.01 PgC yr⁻¹ decade⁻¹) in the equatorial region is yet to be resolved. The rate of anthropogenic CO₂ accumulation from GOBMs is +0.76 ± 0.17 PgC yr⁻¹. This is nearly balanced with the anthropogenic CO₂ flux and is also encompassed by the previous observation-based estimates.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143900964","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":"Midwestern N2O Emissions Linked at Regional Scales to Remotely Sensed Soil Moisture in a North American Inversion","authors":"Cynthia Nevison,&nbsp;Lei Hu,&nbsp;Stephen M. Ogle,&nbsp;Alisa Keyser,&nbsp;Xin Lan,&nbsp;Kathryn McKain","doi":"10.1029/2024GB008418","DOIUrl":"https://doi.org/10.1029/2024GB008418","url":null,"abstract":"<p>The interactions between soil moisture (SM), agricultural practices, and microbially driven N₂O emissions have been described in detail at the field scale. The relationships among those variables are investigated here at larger scales using Soil Moisture Active-Passive remote sensing data and a regional atmospheric inversion. In the atmospheric N₂O data set used in the inversion, 13 large pulse events were observed during the crop growing season from 2015 to 2021 in the U.S. Midwest, mainly in Iowa. These events were linked to rapid changes in SM, either increasing from dry to wet conditions, or vice versa, within a week preceding the N₂O pulse. However, no significant correlations were found between SM or soil temperature and posterior N₂O fluxes from the inversion integrated over Iowa across the peak emission months of May–June. Analysis over the full growing season suggested compensating emissions, for example, higher than normal N₂O fluxes in July following a dry June. These results suggest a relatively consistent ∼4% yield of N₂O from anthropogenic N inputs to croplands in Iowa regardless of short-term variability in soil conditions. Net growing season N₂O emissions in the DayCent biogeochemistry model were also not correlated to SM or temperature, although the model tended to underestimate interannual variability relative to the inversion. An expanded atmospheric observation network, together with an extended SM time series, would allow a better understanding of the relationship between variability in SM and N₂O emissions at regional scales.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888930","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":"Controls on Dissolved Cu Concentrations and Isotopes in the North Atlantic: The Importance of Continental Margins","authors":"Nolwenn Lemaitre,&nbsp;Marion Lagarde,&nbsp;Derek Vance","doi":"10.1029/2024GB008453","DOIUrl":"https://doi.org/10.1029/2024GB008453","url":null,"abstract":"<p>Copper (Cu) is a marine micronutrient whose distribution and budget remain incompletely understood. Here, we present a section of dissolved Cu isotope compositions (δ⁶⁵Cu) across the North Atlantic (GEOVIDE cruise, GEOTRACES GA01). High δ⁶⁵Cu are observed in surface waters and co-vary with carbon uptake rates, indicating light Cu removal by biological activity or complexation of heavy Cu by organic ligands. Beneath the surface, low δ⁶⁵Cu may be partially caused by remineralization. Below 1,500 m, an increase in δ⁶⁵Cu points to removal by particulate scavenging. At greater depths, reversible scavenging, driven by high vertical particulate exports, could explain the increase in Cu concentrations between the surface and deep ocean, mostly in the eastern part of the transect. Investigation of external sources and sinks reveals that anthropogenic aerosols and benthic processes locally supply isotopically light Cu to the ocean, whilst hydrothermal activity above the Reykjanes ridge does not seem to represent a significant source. A striking feature is the low δ⁶⁵Cu observed between 300 and 1,500 m from the Iberian margin to the Icelandic basin, which coincides with elevated non-conservative dissolved neodymium fractions (Nd_xs). This comparison suggests that margin inputs are a source of light Cu to the ocean, and that this Cu can be transported over long distances. The Iberian margin is a hotspot of internal tides and their energy triggers sediment resuspension, leading to particle dissolution and Cu release. These results suggest that continental margins contribute significantly to the missing source of light Cu in the ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008453","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888929","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":"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}