Journal of Geophysical Research-Oceans最新文献

{"title":"Basal Melt Rate Variability and Tidal Current Vertical Structure From Observations Beneath Ronne Ice Shelf, Antarctica","authors":"J. Anselin,&nbsp;K. W. Nicholls,&nbsp;P. R. Holland,&nbsp;J. R. Taylor,&nbsp;S. Østerhus,&nbsp;K. Makinson","doi":"10.1029/2025JC022524","DOIUrl":"10.1029/2025JC022524","url":null,"abstract":"<p>This study examines the interplay between water column structure, tidal currents, and basal melting at a site beneath Ronne Ice Shelf, using a 3-year data set of oceanographic measurements, and a collocated year-long time series of radar-derived melt rate estimates. Currents at the site are characterized by mixed semidiurnal tides with strong spring-neap variability, superimposed on a nontidal flow. The product of current speed and thermal driving, both measured approximately 19 m from the ice base, explains 88% of the melt rate variability. Although current speed is the dominant driver of this variability, thermal driving also contributes non-negligibly on spring-neap and longer timescales. The semidiurnal tidal ellipses feature marked vertical variations, transitioning from nearly rectilinear in the mid-water column to more circular and clockwise (CW)-rotating near the ice. This depth-dependence of the semidiurnal tide is attributed to the differential influence of boundary friction on the CW and anticlockwise (ACW) rotary components near the critical latitude (where the tidal frequency equals the Coriolis frequency). A theoretical model, which assumes depth-independent eddy viscosity, successfully reproduces the observed 3-year mean vertical structure of the tidal ellipses. Considering the total tidal current rather than individual constituents, ice base friction damps both the time-mean flow speed and the tidal fluctuations, with attenuation varying over the spring-neap cycle, peaking during spring tides. The observed latitude- and time-dependent effects of ice base friction on the barotropic tide are not captured in parameterizations that estimate tide-induced friction velocity by scaling the time-averaged barotropic tidal speed with a constant drag coefficient.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JC022524","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144782668","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":"Estuarine Exchange Flow in the Albemarle-Pamlico Estuarine System","authors":"Dongxiao Yin,&nbsp;Courtney K. Harris,&nbsp;John C. Warner","doi":"10.1029/2024JC021919","DOIUrl":"10.1029/2024JC021919","url":null,"abstract":"<p>Estuarine exchange flow controls the salt balance and regulates biogeochemistry in an estuary. The Albemarle-Pamlico estuarine system (APES) is the largest coastal lagoon in the U.S. and historically susceptible to a series of environmental issues including salt water intrusion and eutrophication, yet its estuarine exchange flow is poorly understood. Here, we investigate the estuarine exchange flow in the APES, its tributary estuaries (Pamlico and Neuse), and sub-basin Albemarle Sound using the total exchange flow analysis framework based on results from a deterministic numerical model. We find the following: (a) Dynamics controlling estuarine exchange flow in the APES vary spatially and depend on timescales considered. At inlets, estuarine exchange flows respond to both tidal prism and residual water levels at weather-to-spring/neap timescales. At a long quasi-steady timescale represented as annual means, estuarine exchange flow is dominated by barotropic flow. Within the tributary estuaries, estuarine exchange flows at timescales of wind periods are controlled by wind-induced straining, whereas the quasi-steady state condition is dominated by gravitational circulation. At Albemarle Sound, exchange flow is dominated by the residual water levels at weather-to-spring/neap timescales, while at quasi-steady state it is controlled by barotropic flow. (b) At the quasi-steady annual timescale, the salt content decreases with river discharge. At the weather-to-spring/neap timescales, salt content is insensitive to variations in estuarine exchange flow, except for within Albemarle Sound. (c) Estuarine exchange flow likely influences the biogeochemistry of the APES by playing a key role in regulating the flushing efficiency and material exchange, a role that has been previously overlooked.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021919","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144767418","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":"Wind-Driven Iron Supply by Ekman Buoyancy Flux Enhances Phytoplankton Bloom in the Antarctic Circumpolar Current","authors":"R. Mole,&nbsp;W. J. von Appen,&nbsp;H. Becker,&nbsp;F. A. Haumann,&nbsp;T. Kanzow,&nbsp;A. Piñango,&nbsp;J. Stimpfle,&nbsp;S. Trimborn,&nbsp;E. F. Young","doi":"10.1029/2025JC022530","DOIUrl":"10.1029/2025JC022530","url":null,"abstract":"&lt;p&gt;The Southern Ocean today is a globally relevant sink for atmospheric carbon dioxide (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;), where the biological uptake of carbon through primary productivity is largely controlled by widespread iron (Fe) limitation. We analyze observations from a submesoscale-resolving cross-section of the Antarctic Circumpolar Current (ACC) obtained around one thousand kilometers downstream of South Georgia in the Atlantic sector during austral spring 2022. Vertically integrated chlorophyll peaked in a strong (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;250 mgChl-a m&lt;sup&gt;−2&lt;/sup&gt;) phytoplankton bloom within the central portion of the jet associated with the Southern ACC Front. We infer that winds drove a northward Ekman transport of dense water across the front and that this destabilized the water column, leading to an Ekman Buoyancy Flux (EBF) and enhanced vertical mixing (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;mo&gt;×&lt;/mo&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $1times 10$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;&lt;sup&gt;−2&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt; s&lt;sup&gt;−1&lt;/sup&gt;) across the base of the mixed layer. Using in situ measurements of dissolved iron, we estimate a net flux to the bloom of up to 3 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;μ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${upmu }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;molFe m&lt;sup&gt;−2&lt;/sup&gt;d&lt;sup&gt;‒1&lt;/sup&gt; from a subsurface pool. This large flux can supply the same amount of Fe per unit area in one day as that supplied to the upstream Georgia Basin bloom through deep wintertime entrainment in 1 year. We calculate the bloom's daily Fe demand from in situ &lt;sup&gt;55&lt;/sup&gt;Fe uptake measurements by phytoplankton and find it to be of a similar order of magnitude as the EBF-driven supply. We conclude that the bloom's strength and compact latitudinal extent are explained by EBF. Thus, EBF represents a previously understudied mechanism, which contributes to bloom patchiness and modulates biologically mediated &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;ms","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JC022530","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144767876","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":"Direct Pathways From the Drake Passage to the South Atlantic Subtropical Gyre","authors":"Anna Olivé Abelló,&nbsp;Josep L. Pelegrí,&nbsp;Mariona Claret","doi":"10.1029/2024JC021494","DOIUrl":"10.1029/2024JC021494","url":null,"abstract":"<p>Lagrangian simulations based on 18 years (2002–2019) of high-resolution thermohaline and three-dimensional velocity fields allow revisiting the fate and thermohaline changes of the upper-ocean Antarctic Circumpolar Current (ACC) waters that enter directly the South Atlantic Ocean basin. An advection-diffusion scheme, applied to both climatological annual-mean and daily mean fields, allows estimating the mean pathways and seasonal variability, as well as recirculation volume transports, times, and depths in the South Atlantic subtropical gyre (SASG). The annual-mean diffusive simulation shows that 96.5 Sv of the upper-ocean waters (up to the 28.00 kg m⁻³) crossing the Drake Passage remain in the ACC, while 13.0 Sv join the eastern margin of the SASG. About 8.6 Sv of this eastern input, plus an additional 2.7 Sv that enter the SASG through the interior ocean, reach the North Brazil Current, yielding a total Drake contribution of 11.2 Sv to the upper returning-limb of the Atlantic Meridional Overturning Circulation. The upper-ocean waters that reach the eastern SASG undergo substantial water mass transformations, with a net transfer of 6.7 Sv from intermediate-deep to surface layers and an increase in heat transport by 0.39 PW and salt transport by 8.5 × 10⁶ kg s⁻¹, but remain largely unchanged as they drift westward toward the western boundary at 21°S. Most waters within the SASG (86%) recirculate once, taking a median of 9.1 years, although some complete as many as three loops after reaching 32°S-W. Regarding seasonality, the transit times and transport fraction of the upper-ocean waters flowing into the SASG show higher variability than those remaining in the ACC path.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021494","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144758560","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":"A Large-Eddy Simulation Study on Effects of Wave Shape and Phase-Lag in Oscillatory Sheet Flow","authors":"Antoine Mathieu,&nbsp;Julien Chauchat,&nbsp;Cyrille Bonamy,&nbsp;Tian-Jian Hsu","doi":"10.1029/2025JC022461","DOIUrl":"10.1029/2025JC022461","url":null,"abstract":"<p>The effect of wave shape on sediment transport in the sheet flow regime is investigated using a large-eddy simulation (LES) Eulerian two-phase flow model. The numerical model is first validated with measured data from oscillating water tunnel for medium and fine sand sheet flows driven by velocity-skewed and acceleration-skewed flows. Simulation results are used to explain observed distinct behaviors of a net positive (or negative) transport rate for medium (or fine) sand driven by velocity-skewed flows and an increase of positive transport rate in fine sand driven by acceleration-skewed flows relative to that of medium sand. Model results show that the phase-lag effect typically used to explain these behaviors not only depends on the magnitude of settling velocities but also correlated with sheet flow instabilities occurred at different instants, depending on wave shapes, which enhance sheet flow layer thickness and the importance of suspended load. The phase-lag effect also causes an imbalance of pickup and deposition flux between the crest and trough intervals and the resulting net transport is related to the phase when the deposition flux becomes dominant.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751449","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":"Quantification of Antarctic Bottom Water Pathways in the Australian-Antarctic Basin","authors":"P. Sholeninova,&nbsp;A. K. Morrison,&nbsp;A. McC. Hogg,&nbsp;A. Foppert","doi":"10.1029/2024JC022305","DOIUrl":"10.1029/2024JC022305","url":null,"abstract":"<p>Antarctic Bottom Water (AABW) formation drives the lower limb of the meridional overturning circulation, influencing the Earth's climate, carbon cycle, and marine biological productivity. Recent findings suggest that AABW across the Southern Ocean is changing, including freshening, warming and thinning. These changes motivate the need for process-based understanding of AABW circulation and variability. However, the harsh Antarctic environment limits in-situ observations, making high-resolution models an essential tool for investigating AABW. This study examines AABW varieties from the Ross Sea and the continental shelf adjacent to the Adélie Land coast in the Australian-Antarctic Basin. We explore their interactions and pathways using passive dye-like tracers in an ocean–sea ice model. Our findings reveal that, despite higher volume transport across the shelf break, RSBW contributes less to the basin's ventilation compared to ALBW. This is due to the presence of alternative pathways that divert RSBW eastward and its significant mixing with ambient waters along the continental slope. In contrast, ALBW plays a more prominent role in ventilating the abyssal waters of the basin, a conclusion supported by recent Deep Argo observations. We also found that when RSBW first encounters ALBW along the slope, it vertically overrides ALBW due to its relatively lower density at this stage.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC022305","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144740160","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":"Interannual Variability of the Polar Front Surface Thermohaline Properties in the Barents Sea","authors":"Nicolas Kolodziejczyk,&nbsp;Camille Lique,&nbsp;Jacqueline Boutin,&nbsp;Jean-Luc Vergely,&nbsp;Gilles Reverdin","doi":"10.1029/2024JC021962","DOIUrl":"10.1029/2024JC021962","url":null,"abstract":"<p>The Barents Sea (BS) is a hotspot of Atlantification of the Arctic Ocean, exhibiting a large sea ice decline and ocean warming over the past decades. In the northern BS, these changes may have strongly impacted the Polar Front (PF), the natural frontier between the hydrological, biogeochemical, ecological, and sea ice conditions of the Atlantic and Arctic Ocean. In summer, the sea surface salinity (SSS) gradient provides a better identification of the PF rather than the sea surface temperature gradient, but the interannual mechanisms driving the PF change remain unclear. In this study, taking advantage of the recent development of the CCI + SSS L-band satellite product, we can monitor, for the first time, the interannual variability of SSS signature of the PF during late summer over the period 2010–2022. Satellite measurements reveal that the interannual variability of the PF intensity in September is driven by a strong SSS variability (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math>1 pss) north of the front. The interannual SSS anomalies are mainly explained by the surface freshwater flux associated with the local melt of the imported sea ice. Moreover, the intensity of the PF has likely decreased over the past several decades as a result of the reduction of sea ice import into the northern BS. Since mid-2,000's, more intermittent surface melting may have been the main source of freshwater north of the PF during summer. This may help to preserve the lower SSS Arctic conditions of the northern BS in the context of the Atlantification.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021962","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144740436","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":"Satellite Observed Diurnal Internal Tide Beams in the Northwestern Pacific Ocean","authors":"P. Zhang,&nbsp;Z. Xu,&nbsp;J. You,&nbsp;B. Yin,&nbsp;X. Li","doi":"10.1029/2024JC021363","DOIUrl":"10.1029/2024JC021363","url":null,"abstract":"<p>Through a combination of plane wave analysis and two-dimensional band-pass spatial filtering, multisourced diurnal internal tide beams in the northwestern Pacific Ocean were identified and investigated using 27 years of multi-satellite altimeter data. Along the Pacific western boundary, both the strait-type and slope-type topographies were found to radiate mode-1 internal tides into the Philippine Sea basin. Satellite altimetry revealed that the Taiwan Island slope is a significant source for diurnal internal tides, which is distinct from the Luzon Strait. The diurnal internal tides in the basin exhibit a notable North-South asymmetry due to both propagation and interference. In the northern region, these tides display a long-range progressive nature, emanating mainly from the Luzon Strait and its vicinity. Conversely, in the southern region, the most significant source is the Miangas Ridge, with the secondary source at the northern sill of the Halmahera Sea. These tides converge around 600 km east of Mindanao, forming a nodal and anti-nodal interference pattern. This study presents an observed energy flux mapping for multisourced diurnal internal tides. It highlights slope-type sources along the ocean boundary in generating and shaping diurnal internal tide spatial pattern, a source topography type which is generally not favorable for semidiurnal internal tide generation among the global ocean.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144740474","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":"A Preface to the Special Collection on Regional Sea Level Change and Society","authors":"D. Stammer,&nbsp;Kathy McInnes,&nbsp;Natalya Gomez,&nbsp;Athanasios T. Vafeidis","doi":"10.1029/2025JC023124","DOIUrl":"10.1029/2025JC023124","url":null,"abstract":"<p>Sea-level rise is an existential threat to coastal residents around the world as it progressively raises water levels, promoting increased flooding, erosion, salinization, and ecosystem degradation and loss. Unmitigated climate change will lead to rapid acceleration, with a meter of rise by 2,100 appearing likely and larger rises possible. Although some coastal areas are already being inundated, many others will increasingly suffer from rising sea level and more intense extreme water levels during high tides, winter storms, and hurricanes in the future. Small islands, deltas, and coastal cities are particularly threatened.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JC023124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716922","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":"Zooplankton Size Structure and Energy Transfer Characteristics Under the Influence of Mesoscale Eddies in the Northern South China Sea During Spring: Insights From ZooScan Imaging","authors":"Shuo Wang,&nbsp;Fang Zhang,&nbsp;Xupeng Chi,&nbsp;Qiao Li,&nbsp;Wenxiao Zang,&nbsp;Song Sun","doi":"10.1029/2025JC022560","DOIUrl":"10.1029/2025JC022560","url":null,"abstract":"<p>Mesoscale eddies are key oceanographic features influencing zooplankton community structure and ecosystem function. However, the vertical impacts of cyclonic and anticyclonic eddies on zooplankton energy transfer efficiency remain unclear in the northern South China Sea (SCS). We conducted a field survey in April 2023, collecting zooplankton samples with a multi-net system and analyzing them via ZooScan imaging technology. Size-based and trophic indicators—including the normalized biovolume size spectrum (NBSS), size diversity, and average equivalent spherical diameter (ESD)—were used to assess energy transfer efficiency across depth layers and eddy types. Results indicated significantly higher zooplankton total abundance, biovolume, and carbon biomass within cyclonic eddies (mean ± SD: 93.2 ± 25.7 ind./m³, 45.4 ± 20.9 mm³/m³, 2.9 ± 1.5 mg C/m³) compared to anticyclonic eddies (mean ± SD: 82.2 ± 23.0 ind./m³, 37.8 ± 14.0 mm³/m³, 2.4 ± 0.9 mg C/m³) in the upper 300 m. Small copepods dominated all depth layers in both eddy types, comprising over 70% of the total abundance. Functional indicators, including the NBSS slope, size diversity, and average ESD, indicated higher energy transfer efficiency in cyclonic eddies within the upper 300 m. However, at the 0–25 m depth layers, anticyclonic eddies exhibited flatter NBSS slopes and higher size diversity than cyclonic eddies. Zooplankton productivity declined consistently with depth, while energy transfer efficiency to higher trophic levels showed a fluctuating vertical pattern and tended to rebound in deeper layers. Our findings highlight the crucial role of mesoscale eddy dynamics in structuring zooplankton communities and regulating energy flow in pelagic ecosystems of the northern SCS.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 8","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716925","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}