Journal of Geophysical Research-Oceans最新文献

{"title":"Cold Spells, Fresh Waves, and the Biogeochemical Response in the North Atlantic Cold Anomaly Region","authors":"Fatma Jebri,&nbsp;Zoe L. Jacobs,&nbsp;Meric Srokosz,&nbsp;Ekaterina Popova,&nbsp;Susan E. Hartman,&nbsp;Simon A. Josey","doi":"10.1029/2024JC022001","DOIUrl":"https://doi.org/10.1029/2024JC022001","url":null,"abstract":"<p>Regional effects of marine cold spells (MCS, periods of anomalous cooling), their impact on ecosystem biogeochemistry, and link to salinity extremes remain underexplored. A case in point is North Atlantic's Cold Anomaly (CA) region (known as the “cold blob”), which hits record low temperatures during 2014–16 while most of the global ocean warmed. Using up to 42 years of observations, we characterize the CA as a manifestation of both MCS and Fresh Waves (FW, low salinity extremes) and analyze the surface biogeochemical response. We observe a quasiperiodic pattern of MCS from the 1980s and FW (at least) from the 1990s to early 2020s in the CA region with alternations from cool and freshwater to warm and saline conditions. Since 1990s, the CA region appears to be potentially undergoing MCS and FW compound events that are more frequent and prolonged but less intense than other North Atlantic areas. The 2014-16 CA was among the most widespread and prolonged MCS and FW events associated with a deeper mixed layer and distinct biogeochemical signature, including elevated nutrients and oxygen, an overall increased chlorophyll-a and intensified ocean acidification. These results suggest that MCS could mitigate certain climate change effects through cooling and enhanced productivity, while exacerbating others such as ocean acidification. We compare 2014–16 CA region effects with those of Pacific's warm blob, identifying contrasting behaviors from physical processes to biogeochemical impacts and discussing a common atmospheric driver. Our findings emphasize the need to further study ecological responses to MCS in the North Atlantic.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC022001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822088","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":"Mooring-Observed Cross Equator Propagation of Kelvin Waves Through the Makassar Strait","authors":"Tengfei Xu,&nbsp;Shujiang Li,&nbsp;Yingyi Yang,&nbsp;Yaohua Zhu,&nbsp;A. Kuswardani,&nbsp;Yonggang Wang,&nbsp;Guanlin Wang,&nbsp;Xiaoqing Xu,&nbsp;Fei Teng,&nbsp;Agus Setiawan,&nbsp;Priyadi Dwi Santoso,&nbsp;Teguh Agustiadi,&nbsp;Mukti Trenggono,&nbsp;R. Dwi Susanto,&nbsp;Zexun Wei","doi":"10.1029/2024JC022310","DOIUrl":"https://doi.org/10.1029/2024JC022310","url":null,"abstract":"<p>The propagation of intraseasonal Kelvin waves in the Indonesian seas significantly modulates the Indonesian Throughflow (ITF) transport. However, their northward propagation across the equator within the main ITF route, particularly through the Makassar Strait, has remained unverified due to a lack of in situ observations. This study presents simultaneous mooring observations of current velocity profiles at the choke points in the ITF's main pathway, from the Lombok Strait to the northern Makassar Strait. Our results confirm the propagation of intraseasonal Kelvin waves cross the equator reaching the northern Makassar Strait, primarily along the 100-m isobath. During the propagation, the dominant modes are the first and second baroclinic modes in the Indian Ocean, the second and third baroclinic modes between the Lombok and southern Makassar Straits, and the third to fifth baroclinic modes between the southern and northern Makassar Straits. Vertical mode decomposition reveals that the intraseasonal velocity anomaly in the northern Makassar Strait comprises the first five baroclinic modes, with the first two modes dominant in the upper 400 m and the third to fifth modes dominant at depths of 400–800 m. Our finding establishes the Makassar Strait as a definite pathway for the cross-equator propagation of Kelvin waves, linking wave dynamics between the Pacific and Indian Oceans.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822117","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":"Comparing the Role of Floe Breakage and Melt on Summer Sea Ice Loss","authors":"Rigoberto Moncada,&nbsp;Mukund Gupta,&nbsp;Andrew F. Thompson,&nbsp;Jose E. Andrade","doi":"10.1029/2024JC021223","DOIUrl":"https://doi.org/10.1029/2024JC021223","url":null,"abstract":"<p>Marginal ice zones are composed of individual sea ice floes, whose breakage and melt influence its dynamical behavior. These processes are not well represented by global or regional climate models due to the continuum approximations and uncertainties regarding forcing, data resolution and parameterizations used for sea ice. Here, we use a Discrete Element Model (DEM) coupled to a slab thermodynamic ocean to investigate how breakage and melt processes impact the decay of summer sea ice. The DEM is calibrated using MODIS satellite imagery and reanalysis data within the Arctic Ocean's Baffin Bay during June–July 2018. The sensitivity of the sea ice decay is evaluated by varying the solar heating, the ice/ocean heat exchange parameter, and a prescribed floe breakage rate. For the parameter regime that best fits observations, the ratio of mass loss of resolved floes (diameter <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math>2 km) due to breakage versus melt is 0.47, and oceanic versus solar melt is 0.46. The rate at which resolved floes lose mass is most sensitive to the breakage rate, as compared to the solar and oceanic melt parameters. The number decay of the largest floes (<i>D</i> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math>21 km) is controlled by breakage, whereas the decay of smaller floes (<i>D</i> = 2–21 km) depends strongly on lateral and basal melt. Inferences from this exploration of the parameter space may help motivate more accurate parameterizations of the floe size distribution evolution in climate models.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822316","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":"Role of Midwater Mixed Waves in the Loop Current Separation Events From a Coupled Ocean-Atmosphere Regional Model and In Situ Observations","authors":"Xiao Ge,&nbsp;Steven F. DiMarco,&nbsp;Yun Liu,&nbsp;Ping Chang,&nbsp;Dan Fu,&nbsp;Jaison Kurian,&nbsp;Chuan-Yuan Hsu,&nbsp;Anthony H. Knap","doi":"10.1029/2024JC021330","DOIUrl":"https://doi.org/10.1029/2024JC021330","url":null,"abstract":"<p>A previously uninvestigated necking-down region in the Gulf of Mexico, associated with the Loop Current eddy (LCE) separations is defined by the 8–16 days variance below the Loop Current system (LCS) around 88.5°W, using an Ocean-Atmosphere Coupled Regional-Community Earth System Model (R-CESM) 9-year nature run, which reveals the mechanisms of Loop Current (LC) deep dynamics. Scaled wavelet analysis of flow fields in five regions at the 27.5 kg/m³ potential density layer under the LCS shows that the 8–16 days variance is reproduced by the R-CESM model dynamics, aligning with in situ observations. This weather band deep variance, identified as the mixed waves located between the mixed Rossby-gravity waves and Rossby waves in the ocean wave dispersion relationship, is stimulated by the interaction between the penetrating LC and steep topography. Then, these waves are released from the constraints of the topography and become free wave trains. There are three critical regions for the propagating wave trains: the Mississippi Fan, the Yucatan Shelf, and the Florida Escapement. The various wave trains define five distinct scenarios: East Yucatan Shelf (EYSS), West Yucatan Shelf (WYSS), west Florida escarpment (WFES), Mississippi Fan (MFS), and quiescent (QS) scenarios. The scenarios passing through the west necking-down region can be used to indicate the LCE separations. After the separations, the retracted LC may encounter interference from either the EYSS or the WFES, preventing the reattachments. These 8–16-day waves offer insights into describing the LC shedding events from the lower layer of the LCS, enhancing the understanding of LCS dynamics.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021330","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818372","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":"Weakened Eddy Activities in the South Pacific Subtropical Countercurrents Under Global Warming","authors":"Ningyuan Xiao,&nbsp;Shengpeng Wang,&nbsp;Chen Yang,&nbsp;Fengfei Song,&nbsp;Zhao Jing,&nbsp;Lixin Wu","doi":"10.1029/2024JC022128","DOIUrl":"https://doi.org/10.1029/2024JC022128","url":null,"abstract":"<p>The subtropical countercurrent (STCC), located near the South Pacific boundary, exhibits a band of high eddy activities. These eddies have significant implications on the exchanges of heat, salt, volume, and biogeochemical properties. Yet their response to greenhouse warming change remains unknown. Using an ensemble of long-term high-resolution climate simulations under a high carbon emission, we show that eddy kinetic energy (EKE) in the STCC is projected to be significantly reduced in a warming climate. This reduction primarily stems from weakened baroclinic instability of the STCC-South Equatorial Current (SEC) system, which is associated with a projected decrease in vertical velocity shear and an increase in upper ocean stratification. The former majorly results from an enhanced meridional salinity gradient due to the reduction in subtropical precipitation, whereas the latter is caused by an enhanced thermal stratification associated with a faster surface warming in a warming climate. The findings of this study will contribute to a better understanding of the impact of climate change on ocean motions as well as their climate impact near the western boundary.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC022128","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818431","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":"Trends and Variability in Depth and Spiciness of Subsurface Isopycnals on the Vancouver Island Continental Shelf and Slope","authors":"M. Maier,&nbsp;D. Ianson,&nbsp;R. C. Hamme","doi":"10.1029/2024JC020992","DOIUrl":"https://doi.org/10.1029/2024JC020992","url":null,"abstract":"<p>The waters over the southern Vancouver Island shelf and slope are productive, economically important regions. The circulation is highly dynamic through variable mixing of both younger subarctic and older southern water masses, and significant local upwelling and downwelling regimes. We take advantage of three time series that cover more than three decades: the La-Perouse, Line-P, and CalCOFI time series, each covering at least 37 years (1984–2021). We investigate subsurface salinity, temperature, and depth observations to study seasonal and interannual variability in isopycnal heave and spiciness, and evaluate possible trends. The 26.6 kg m⁻³ isopycnal is the deepest isopycnal that is regularly upwelled onto the Vancouver Island shelf (above 200 m), shoaling over 100 m seasonally. Spiciness on the 26.6 isopycnal is highest in winter, but seasonal variability is much smaller than the interannual variability, which itself is two to three times smaller than the variability in adjacent subarctic waters and in the California Undercurrent further south, prior to their arrival in our study region. Spiciness in subsurface shelf waters appears to have been increasing over the past 37 years, by about half the magnitude of the increase in spiciness observed in the California Undercurrent water. In contrast, the subsurface slope shows no trend in spiciness but appears to be experiencing physical convergence, specifically an increase in the volume of water with a density of around 26.6 kg m⁻³, which has also been observed in the subarctic northeast Pacific, at Ocean Station Papa.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC020992","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818373","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":"Vertical Transport by Frontal Subduction Alleviating Hypoxia in a Highly Stratified Estuary","authors":"Keyan Liu,&nbsp;Jiaxue Wu,&nbsp;Yongsheng Cui,&nbsp;Chao Li","doi":"10.1029/2024JC021932","DOIUrl":"https://doi.org/10.1029/2024JC021932","url":null,"abstract":"<p>Coastal hypoxia often develops in stratified estuaries, primarily caused by the coexistence of river plume expansion and shelf seawater intrusion. Surface fronts generated by tidal plumes are associated with enhanced vertical transport. While previous studies have explored the near-bed impacts of plume fronts, the frontal processes in influencing hypoxic zones caused by the barrier layer are not straightforward. Here, we use remote sensing, shipboard, and mooring observations, aiming to explore the physical dynamics of frontal subduction for alleviating bottom hypoxia. In situ observations were conducted in the highly stratified Pearl River Estuary, a region where surface fronts frequently occur, and significant bottom hypoxia appears during summer. We show that bottom hypoxia can be temporarily alleviated by the rapid water transport driven by frontal subductions. Specifically, the critical mid-field front, trapped by tidal flow reversal, leads to the convergence in the surface layer. A downwelling process is driven by this convergence at the front, subducting surface river-born buoyant material to the bottom. Both dissolved oxygen (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mtext>DO</mtext>\u0000 </mrow>\u0000 <annotation> $text{DO}$</annotation>\u0000 </semantics></math>) and large particles from the river plume are transported to the bottom layer through this subduction, effectively increasing bottom <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mtext>DO</mtext>\u0000 </mrow>\u0000 <annotation> $text{DO}$</annotation>\u0000 </semantics></math> concentrations. This bottom-attached subduction, characterized by weak mixing, moves downward along the sloping isopycnals, a pathway supported by local weak stratification and weak advective forcing during the low tide. Our findings reveal a unique mechanism of the subduction at mid-field fronts, and the specific tidal conditions support this slantwise vertical transport, which further impact coastal hypoxia and particle transport.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818374","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":"Extreme Heatwave Affects the Saltwater Intrusion and River Plume Extension in the Changjiang River Estuary","authors":"Yaoting Lin,&nbsp;Yihe Wang,&nbsp;Jianrong Zhu,&nbsp;Cheng Qiu,&nbsp;Hui Wu","doi":"10.1029/2024JC022287","DOIUrl":"https://doi.org/10.1029/2024JC022287","url":null,"abstract":"<p>In 2022, China experienced an extreme hot summer accompanied by record-breaking droughts. Although extensive attentions have been paid on its influences on the urban and watershed systems, how the heatwave affects the hydrodynamics in marginal seas, which is essential for the environment and security in the coastal area, remains unclear. Here in this study, we examined effects of the heatwave on the Changjiang River Estuary and adjacent shelf seas with a numerical model. The results indicated that direct heating over the sea has dual effects on both saltwater intrusion into the estuary and river plume extension. First, strong heating causes intensified stratification, increasing the potential energy anomaly (PEA) value by approximately 7%. This weakens the vertical mixing, thus maintains a low-salinity in the surface. Second, on the contrary, extreme heating induces strong evaporation, which increases the sea surface salinity. In the estuary area, the heating-induced stratification and evaporation-induced salinization are both in favor of a stronger estuarine circulation, and therefore increase the salinity in the estuary. This worsened the already severe situation of freshwater supplement in that year. In the river plume area, the heating-induced stratification resulted a stronger plume extension, but was overwhelmed by the evaporation-induced salinization. Consequently, the plume area decreased by 8.52%. In contrast, in normal years, precipitation dominates in summer due to the heavy rainfall, and thus the co-work of heating-induced stratification and precipitation-induced freshening further enhances the plume extension. This study contributes to understanding of the interlinked effects of extreme climate events on shelf and estuarine systems.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818427","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":"Satellite-Estimation of the Global Ocean Primary Productivity via BGC-Argo Measurements","authors":"Yinxue Zhang,&nbsp;Xianqiang He,&nbsp;Yan Bai,&nbsp;Guifen Wang,&nbsp;Teng Li,&nbsp;Difeng Wang,&nbsp;Fang Gong,&nbsp;Qiankun Zhu","doi":"10.1029/2024JC021163","DOIUrl":"https://doi.org/10.1029/2024JC021163","url":null,"abstract":"<p>Monitoring the global ocean net primary productivity (NPP) has been the primary objective of satellite ocean color remote sensing since the launch of the world's first satellite ocean color sensor in 1978. However, considerable discrepancies persist in current satellite NPP estimations, and the use of limited in situ data is one of the key challenges for accurate NPP estimation. Here, a global depth-resolved NPP profile (NPP_re) data set was constructed on the basis of 10 years of biogeochemical Argo (BGC-Argo) measurements and a tuned carbon-based productivity model (BGC_CbPM). On the basis of this data set and the XGBoost machine learning model, a global oceanic NPP_re remote sensing inversion model (XGBoost_CbPM) was established for NPP estimation from Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua data. Validation with 14 independent samples revealed a coefficient of determination of 0.87 and a mean absolute percentage deviation of 12.52% between the model predictions and in situ measurements. In addition, the results obtained via the XGBoost_CbPM model suitably agreed with the in situ measurements at two time series stations, namely BATS and HOT. In particular, the time series changes in the NPP derived by the XGBoost_CbPM model at the BATS and HOT stations were better than those of the original satellite products based on the carbon-based productivity model. More importantly, as a depth-resolved model, the XGBoost_CbPM model can provide NPP profiles that are superior to those of traditional NPP models, which can be used to estimate only the water column-integrated NPP. This study underscores the significant contribution of BGC-Argo measurements in enhancing the satellite estimation of the global ocean NPP.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818430","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":"Tracing Macroalgal-Induced Changes in Carbon Dynamics of High-Arctic Fjords Using Biomarker Fingerprinting","authors":"Biswajit Roy,&nbsp;Archana Singh,&nbsp;Manish Tiwari","doi":"10.1029/2024JC021900","DOIUrl":"https://doi.org/10.1029/2024JC021900","url":null,"abstract":"<p>Due to rising seawater temperatures and reduced sea ice extent, the coastal Arctic region is witnessing an expansion of macroalgal forests. However, changes in carbon dynamics resulting from such extensive macroalgal growth are still unknown in the high-Arctic fjords. To trace the macroalgal signatures in Arctic fjords, bulk C-isotopic and compound-specific <i>n</i>-alkane distributions were studied in dominant macroalgae (brown, red, and green) (<i>n</i> = 20) and also surface sediments (<i>n</i> = 13) from the inner to outer regions of Kongsfjorden (Svalbard). The macroalgal species shows variable C-isotopic signature (−17.0‰ to −28.9‰) but similar distribution of long-chain <i>n</i>-alkanes (&gt;<i>n</i>-C₂₃) with no predominance in carbon homologs, supporting environmental induced <i>n</i>-alkyl lipid production compared to the bulk biomass. Despite similar grain size and mineral composition of the fjord sediments, differences in C-isotopic composition and <i>n</i>-alkanes distribution indicate contribution of organic matter from different sources. In the inner and middle fjord region, the C-isotopic distribution (−23.3 ± 1.1‰ to −23.4 ± 1.3‰) and short-to long-chain <i>n</i>-alkanes signatures highlight possible mixing of contribution from phytoplankton, macroalgal-debris, and terrestrial sources. While, in the outer fjord, significantly lower δ¹³C values (−25.6 ± 0.9‰) and <i>n</i>-alkane distribution similar to macroalgal communities suggest lipid accumulation possibly sourced from the reworking of macroalgal-debris. High sedimentation and microbial breakdown of macroalgal debris create a low-oxygen environment, as evidenced by higher cyclic octasulphur compounds in the inner and middle fjord region. Under future warming conditions, such oxygen-starved regions in Arctic fjords may become more common as macroalgal forests expand and sediment influx increases.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809443","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}