Global Biogeochemical Cycles最新文献

{"title":"Global Patterns of Leaf Litter C:N:P Stoichiometry Under Current and Future Climate Scenarios","authors":"Ji Yuan,&nbsp;Qiqian Wu,&nbsp;Zimin Li,&nbsp;Josep Peñuelas,&nbsp;Jordi Sardans,&nbsp;Changhui Peng,&nbsp;Yan Peng,&nbsp;Yuexin Fan,&nbsp;Petr Heděnec,&nbsp;Chaoxiang Yuan,&nbsp;Nannan An,&nbsp;Fuzhong Wu,&nbsp;Kai Yue","doi":"10.1029/2024GB008431","DOIUrl":"https://doi.org/10.1029/2024GB008431","url":null,"abstract":"<p>Plant litter carbon (C), nitrogen (N), and phosphorus (P) stoichiometry can indicate ecosystem nutrient use efficiency and limitation. Yet, a comprehensive quantification of plant litter C:N:P ratios at the global scale remains elusive, limiting our understanding of how their variation responds to future climate change. We constructed a database comprising 11,807 records of leaf litter C:N:P ratios, quantifying their global patterns under current and future (2041–2100) climate scenarios using the random forest method. We found that global mean leaf litter C:N, C:P and N:P ratios were 46.5, 669.4 and 16, respectively, while they were dependent on mycorrhizal association, taxonomic division, and/or plant functional type. Leaf litter C:N and N:P ratios showed opposite latitudinal patterns, being larger in high and low latitude regions, respectively, while the C:P ratio remained relatively stable in low latitude regions but increased significantly toward the poles. Our simulations further revealed that increasing climate warming decreased the leaf litter C:N ratio but increased the C:P and N:P ratios in terrestrial plants, despite the fact that their variations were largely dependent on ecosystem type. These findings clearly benefit us to understand the role of leaf litter in regulating the cycling of C and nutrients, responding to ecosystem plant development with climate change.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085303","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":"Stable Iron Isotopes Constrain the Sedimentary Input of Dissolved Iron to the Ocean","authors":"Ying Ye,&nbsp;Christoph Völker","doi":"10.1029/2024GB008373","DOIUrl":"https://doi.org/10.1029/2024GB008373","url":null,"abstract":"<p>Iron is a key micronutrient for marine biota and potentially one of the main drivers of ocean feedback to changing climate. There is however no consensus on the relative role of different external iron sources to the ocean, hampering our ability to predict how the oceanic iron cycle and biological carbon pump will react to climate change. For the last two decades, stable iron isotopes have been increasingly used in field studies to track contributions of different iron sources and modeling studies started to help interpreting isotope observations. However, measured isotopic compositions of iron sources can vary substantially, and the isotopic signatures of different sources can overlap, leading to high uncertainty in constraining the magnitude of the sources. This study aims to examine the sensitivity of seawater iron isotopes to the uncertainty in the sedimentary source. An existing box model of the marine carbon cycle is extended with a description of the cycle of iron and its stable isotopes. Experiments have been done with variable isotopic end-member signature and strength of the sedimentary source, and fractionation through biological uptake and binding to organic ligands. The model results reveal the necessity to consider spatially distinct isotopic end-member signatures for the sedimentary source and fractionations so as to reproduce observed spatial gradients of seawater iron isotopic composition. By assuming a sedimentary input of 7.5–15 Gmol Fe <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mtext>yr</mtext>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${text{yr}}^{-1}$</annotation>\u0000 </semantics></math>, the model is able to reproduce observed concentrations of dissolved iron and its isotopes in large ocean regions, providing useful constraints for complex global biogeochemistry models.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008373","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085501","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":"Contrasting Drivers of Bacterial Metabolism in the Euphotic and Mesopelagic Zones of Tropical Oligotrophic Oceans","authors":"Wenxin Fan,&nbsp;Wupeng Xiao,&nbsp;Chao Xu,&nbsp;Zengchao Xu,&nbsp;Yao Liu,&nbsp;Weinan Li,&nbsp;Jiayu Guo,&nbsp;Chengwen Xue,&nbsp;Jixin Chen,&nbsp;Xin Liu,&nbsp;Bangqin Huang","doi":"10.1029/2024GB008388","DOIUrl":"https://doi.org/10.1029/2024GB008388","url":null,"abstract":"<p>Microbial metabolism plays a critical role in global carbon cycling; however, our understanding of bacterial metabolic processes across the full depth of tropical oligotrophic oceans remains incomplete. The South China Sea (SCS) and Western Pacific (WP), as contrasting oligotrophic environments, provide an ideal setting to investigate this unresolved issue. This study presented a comprehensive analysis of bacterial carbon demand (BCD) from the euphotic to the mesopelagic zone in both regions, revealing distinct drivers of bacterial metabolism at different depths. In the euphotic zone, BCD was closely linked to biotic factors such as bacterial abundance and net primary production, with the SCS exhibiting higher bacterial metabolic activity compared to the WP. Below the euphotic zone, dissolved organic carbon availability became the critical limiting factor, with the WP supporting stronger bacterial metabolism due to more efficient organic matter retention. These findings highlighted the regional variability in carbon sequestration efficiency between the SCS and WP, offering new insights into the marine biological carbon pump. As climate change intensifies, understanding how microbial metabolism modulates carbon export and long-term storage is increasingly critical for predicting shifts in the carbon sink capacity of marine ecosystems.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074268","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":"The Unaccounted Oceanic Sink of Anthropogenic Nitrous Oxide and Its Relationship With Anthropogenic Carbon Dioxide","authors":"Mercedes de la Paz,&nbsp;Antón Velo,&nbsp;Reiner Steinfeldt,&nbsp;Fiz F. Pérez","doi":"10.1029/2024GB008417","DOIUrl":"https://doi.org/10.1029/2024GB008417","url":null,"abstract":"<p>Since 1800, the concentration of greenhouse gases like nitrous oxide (N₂O) and carbon dioxide (CO₂) has significantly increased due to anthropogenic activities. Oceanic anthropogenic CO₂ (C_ant) uptake from the atmosphere has been quantified and periodically re-evaluated given the implications for climate change. However, the potential oceanic uptake of N₂O has been largely overlooked. This study quantifies the uptake of N₂O of anthropogenic origin (N₂O_ant) taken up by the global ocean and how it relates with the anthropogenic CO₂. The oceanic inventory of N₂O_ant has been quantified using two approaches which consider the anthropogenic perturbation of N₂O and CO₂ as conservative tracers: first, a direct approach using the Transient Time Distribution (TTD) method; and second, indirectly through a novel method, founded on the direct proportionality between the excess of both N₂O and CO₂ in the atmosphere since 1800. Our results show that the North Atlantic Ocean is a key region of maximum accumulation of N₂O_ant due to the confluence of cold and ventilated waters. The global oceanic uptake of N₂O_ant from the pre-industrial times to 2010 was estimated to be 11.5 ± 2.3 Tg-N, with an annual uptake rate of 0.23 ± 0.05 Tg-N yr⁻¹. The study shows that oceanic sequestration contributes to a small portion of global N₂O inventories, but it is comparable to other N₂O oceanic budget numbers derived from atmospheric nitrogen deposition. Furthermore, connecting the N₂O_ant and C_ant oceanic distributions is a valuable tool for linking the perturbation of the Anthropocene on the N and C cycles in the ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008417","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074270","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":"Deforestation Increases Vegetation Vulnerability to Drought Across Biomes","authors":"Chenwei Xiao,&nbsp;Sönke Zaehle,&nbsp;Stephen Sitch,&nbsp;Gregory Duveiller,&nbsp;Daniel E. Pabon-Moreno,&nbsp;Anthony P. Walker,&nbsp;Jürgen Knauer,&nbsp;Fabienne Maignan,&nbsp;Christiane Schmullius,&nbsp;Ana Bastos","doi":"10.1029/2024GB008378","DOIUrl":"https://doi.org/10.1029/2024GB008378","url":null,"abstract":"<p>Land use and land cover changes have altered terrestrial ecosystem carbon storage, but their impacts on ecosystem sensitivity to drought and temperature fluctuations have not been evaluated spatially over the globe. We estimate drought and temperature sensitivities of ecosystems using vegetation greenness from satellite observations and vegetation biomass from dynamic global vegetation model (DGVM) simulations. Using a space-for-time substitution with satellite data, we first illustrate the effects of vegetation cover changes on drought and temperature sensitivity and compare them with the effects estimated from DGVMs. We also compare simulations forced by scenarios with and without land cover changes to estimate the historical land cover change effects. Satellite data and vegetation models both show that converting forests to grasslands results in a more negative or decreased positive sensitivity of vegetation greenness or biomass to drought. Significant variability exists among models for other types of land cover transitions. We identify substantial effects of historical land cover changes on drought sensitivity from model simulations with a generally positive direction globally. Deforestation can lead to either an increased negative sensitivity, as drought-tolerant forests are replaced by grasslands based on model ensemble mean, or a decreased negative sensitivity, since forests under current land cover are predicted to exhibit greater drought resistance compared to those under pre-industrial land cover. Overall, our findings emphasize the critical role of forests in maintaining ecosystem stability and resistance to drought and temperature fluctuations, thereby implying their importance in stabilizing the carbon stock under increasingly extreme climate conditions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008378","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143950292","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 Role of Ballasting, Seawater Viscosity and Oxygen-Dependent Remineralization for Export and Transfer Efficiencies in the Global Ocean","authors":"Onur Karakuş,&nbsp;Cara Nissen,&nbsp;Christoph Völker,&nbsp;Wilhelm Hagen,&nbsp;Morten Iversen,&nbsp;Laurent Oziel,&nbsp;Özgür Gürses,&nbsp;Judith Hauck","doi":"10.1029/2024GB008403","DOIUrl":"https://doi.org/10.1029/2024GB008403","url":null,"abstract":"<p>The particulate organic carbon (POC) flux from the euphotic zone to the deep ocean is central to the biological carbon pump. It is typically evaluated using “export efficiency” and “transfer efficiency,” which reflect POC formation and sinking and carbon sequestration efficiency in the ocean's interior, respectively. Since observations of these metrics are limited, biogeochemical models can elucidate the controls of large-scale patterns. This study uses the global ocean-biogeochemical model FESOM-REcoM, with a new sinking routine that accounts for ballast minerals, seawater viscosity, and oxygen-dependent remineralization in POC sinking and remineralization, to identify the drivers of global export and transfer efficiency. We find that export efficiency is highest at high latitudes, where diatoms, mesozooplankton, and macrozooplankton dominate the plankton community, but that high export efficiency does not always imply high transfer efficiency. Omitting ballast minerals decreases export efficiency by 20% in the Southern Ocean, yet the globally integrated POC flux out of the euphotic zone (5.4–5.6 Pg C <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mtext>yr</mtext>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${text{yr}}^{-1}$</annotation>\u0000 </semantics></math>) and the global average export efficiency (14.7%–15.4%) are relatively insensitive to seawater viscosity, mineral ballasting, or oxygen-dependent remineralization. In contrast, global transfer efficiency is more sensitive to these processes and varies between 21% and 25% in the simulations, with the largest reduction by 23% observed when omitting ballasting in subtropical, low-productivity regions. Our findings suggest that assumptions about ballasting and background sinking speed could explain previous discrepancies in the literature regarding the highest transfer efficiencies in low or high latitudes. Notably, while plankton community structure determines export efficiency regimes, zooplankton fecal pellets drive high transfer efficiencies in regions with high export efficiency, like the Southern Ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 5","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008403","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143909024","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":"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}