Deep-sea Research Part Ii-topical Studies in Oceanography最新文献

{"title":"Compositional variation and genesis of ferromanganese crusts in the central segment of Emperor Chain Guyots, Pacific Ocean","authors":"Pavel E. Mikhailik ,&nbsp;Irina A. Vishnevskaya ,&nbsp;Liang Yi ,&nbsp;Evgeniy V. Mikhailik","doi":"10.1016/j.dsr2.2025.105507","DOIUrl":"10.1016/j.dsr2.2025.105507","url":null,"abstract":"<div><div>We studied the morphology, mineral composition, and chemical composition of ferromanganese (Fe-Mn) crusts from the central segment of the Emperor Chain Guyots (Jingū, Ōjin, and Nintoku). These Fe-Mn crusts are characterized by a 10 Å manganese phase, amalgamated with vernadite (δ-MnO₂), exhibiting significant variation in their mineralogical composition when compared to those associated with other Pacific seamounts. Notably, these Co-rich crusts are highly enriched in lead, with concentrations reaching up to 5303 ppm and an average of 3029 ppm. They show elevated levels of molybdenum (up to 1429 ppm, with an average of 879 ppm) and tungsten (up to 287 ppm), approximately double those found in other global ocean regions. A remarkable enrichment of rare earth elements and yttrium (REY) was also observed, with a cumulative level of 5431 ppm. The concentrations of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), and nickel (Ni), in combination with the REY distribution patterns, suggest that these Fe-Mn crusts are primarily of hydrogenic origin. Nonetheless, there is evidence of a hydrothermal contribution, particularly linked to the Late Pliocene volcanic rejuvenation phase (3.97–3.21 million years ago) of the Pacific Plate.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105507"},"PeriodicalIF":2.3,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144632665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 behavior of particulate matter in the Persian Gulf: biogeochemical proxies for source identification","authors":"Hamid Ershadifar,&nbsp;Abolfazl Saleh,&nbsp;Kamalodin Kor","doi":"10.1016/j.dsr2.2025.105505","DOIUrl":"10.1016/j.dsr2.2025.105505","url":null,"abstract":"<div><div>The present research study is intended to assess the probable sources of suspended particulate matter (SPM) in the Persian Gulf. SPM was collected at three to four depth resolutions: surface, 10 and/or 25 m, and 2–3 m above the seabed over three research cruises: PGE1901 (May 2019), PGE1902 (November 2019), and PGE2101 (March 2021). The SPM concentration exhibits several maxima along the northern coastline and is higher in winter than spring and autumn. SPM consisted of calcium carbonate (CaCO₃), opaline silica (SiO₂), organic matter, detrital matter from the upper continental crust (UCC), and contaminants derived from industrial activities (e.g., leaking or combustion of fossil fuels). Particulate organic matter (POM) is the major fraction in offshore samples, accounting for up to 84 % of the particulate mass, while the contribution of MnO₂ is lower than 0.1 % during the three seasons. The particulate CaCO₃ content varied more than other major components, being lowest in the northern Strait of Hormuz and up to 40 % in the region near the southern carbonate shelf. Strong coupling among the biochemical parameters Chl-a, bSi, TPP, and TPN was observed during the winter, likely reflecting higher autotrophic contributions to the particulate organic matter (POM). The decrease in TPN from autumn to winter, along with increases in Chl-a and TPP, resulted in three- and two-fold drops in N:Chl-a and N:P ratios, respectively. The concentrations of metal elements decrease in the general order of Ca &gt; Fe &gt; Al &gt; Zn &gt; Ti &gt; Mn &gt; Cr &gt; Cu &gt; Ni &gt; Pb &gt; V &gt; Mo &gt; Cd. Most of the elements exhibit enrichment levels ranging from 50 to 5000 times higher than the values found in the upper continental crust, with notable exceptions for titanium (Ti) and manganese (Mn). Except for cadmium, with a Me/P ratio close to the reported intracellular values, phytoplankton's contribution to the particulate pool of other bioactive trace elements barely exceeds 15 %. The predominant fraction of particulate Pb, Zn, Cu, and Ni is beyond the dust and phytoplankton contribution, possibly from the long-term accumulation of these elements, with some signs of local anthropogenic input.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105505"},"PeriodicalIF":2.3,"publicationDate":"2025-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hard-bottom communities in the deep Fram Strait: patterns, processes, and looming questions","authors":"Kirstin S. Meyer-Kaiser ,&nbsp;Kharis Schrage ,&nbsp;Melanie Bergmann","doi":"10.1016/j.dsr2.2025.105506","DOIUrl":"10.1016/j.dsr2.2025.105506","url":null,"abstract":"<div><div>Hard-bottom habitats, including dropstones and rocky reefs, increase habitat heterogeneity and host unique communities in the Fram Strait. This manuscript synthesizes research on the composition and dynamics of hard-bottom communities over HAUSGARTEN's 25 years, combining known patterns with previously unpublished data. Our research reveals that hard-bottom communities have high biodiversity, including taxa that have not yet been identified or described. Research on reproduction in hard-bottom taxa has been limited. For the most common hard-bottom species, which include sponges, soft corals, and anemones, larvae tend to settle near their parents. Hydroids have much broader-range dispersal and serve as pioneer species in the deep Fram Strait. Results from two novel recruitment experiments (2015–2024, 2019–2024), combined with results from two previous studies, show the process of succession in hard-bottom communities. Initial recruitment of hydroids was followed by tube worms, sponges, and cnidarians, leading to a strong increase in rarefied species richness and differences in species composition over time. Tracking of the hard-bottom fauna on marked stones showed negligible growth and 0–23 % mortality over 5 years (2019–2024). In summary, our research indicates that hard-bottom taxa in the deep Fram Strait have short-range larval dispersal, low recruitment, and slow growth. These characteristics suggest that hard-bottom communities have limited resilience to anthropogenic disturbance.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105506"},"PeriodicalIF":2.3,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biogeochemical float deployment strategy in the Southwestern Indian ocean","authors":"Wilhem Riom ,&nbsp;Vincent Taillandier ,&nbsp;Céline Dimier ,&nbsp;Fabrizio D'Ortenzio ,&nbsp;Hervé Claustre","doi":"10.1016/j.dsr2.2025.105504","DOIUrl":"10.1016/j.dsr2.2025.105504","url":null,"abstract":"<div><div>The recent roadmap <em>IndOOS-2</em> has stressed the need to expand the biogeochemical-Argo observing system in the Indian Ocean. The Monaco Explorations Indian Ocean expedition offered a unique opportunity to meet this goal in the southwestern sector which was, in this regard and at that time, one of the least covered oceanic regions. We designed a deployment strategy for the biogeochemical float array grounded on past experiences, existing knowledge, and the analysis of historical datasets to cover the contrasting biophysical regimes from the Seychelles Chagos Thermocline Ridge to the subtropical gyre. Aligning with IndOOS-2 recommendations, a denser float distribution was set in the tropical band to enhance biogeochemical observations in upwelling zones. Following this strategy, a fleet of seventeen biogeochemical floats was successfully deployed during the expedition in October–November 2022. After two years of operations, the spatio-temporal distribution covered by the fleet confirmed that the goals of the deployment strategy have been reached, revealing seasonal modulations of the meridional trophic gradient with respect to phytoplankton biomass from tropical mesotrophy to subtropical oligotrophy.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105504"},"PeriodicalIF":2.3,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prediction of sardine and anchovy catches by double-boat purse seiners in the northern Persian Gulf using machine learning models","authors":"Elyas Soleimani ,&nbsp;Moslem Daliri ,&nbsp;Ali Salarpouri ,&nbsp;Hossein Zamani","doi":"10.1016/j.dsr2.2025.105502","DOIUrl":"10.1016/j.dsr2.2025.105502","url":null,"abstract":"<div><div>Enhancing the efficiency of small pelagic purse-seine fisheries is essential for promoting responsible fisheries management in the Persian Gulf. Therefore, this study forecasts the spatiotemporal catch variations of Sind sardinella (<em>Sardinella sindensis</em>) and Buccaneer anchovy (<em>Encrasicholina punctifer</em>) caught by double-boat purse seiners in the northern Persian Gulf, Qeshm Island. To achieve this, a dataset comprising fishing records from 314 purse seine operations, along with associated environmental parameters obtained from satellite imagery—including sea surface temperature (SST), chlorophyll-a concentration, photosynthetically active radiation (PAR), wind speed, wind direction, depth, and distance—was compiled and analyzed using an advanced machine learning methodology covering the period from September 2014 to October 2023. The evaluation of the regression models used to predict sardine and anchovy catches—including Random Forest (RF), Boosting, and Support Vector Regression (SVR)—revealed varying levels of predictive performance across both species and model types. In the case of sardine, the Boosting Regression model yielded the highest predictive accuracy, characterized by a relatively low error (RMSE = 395.5) and moderate explanatory power (R² = 0.41). Conversely, for anchovies, the SVR model with a radial basis function (RBF) kernel demonstrated superior performance relative to the other models, with an RMSE of 437 and an R² of 0.35. The results suggest that anchovy catch prediction was more challenging and potentially influenced by additional unmodeled variables. The CPUE of sardine increases with rising chlorophyll-a concentrations up to approximately 2 mg/m³, but declines beyond this point. The optimal SST range was between 22 °C and 26 °C, whereas sardine catches declined at temperatures exceeding 30 °C. Because anchovy was consistently present across all sampling sets, distance from the shoreline emerged as the most influential parameter contributing to successful net captures. A negative relationship was observed between this factor and anchovy CPUE. As the second most important variable, the optimal SST range for anchovy was similar to that of sardine. Given the substantial fishing effort in the northern Persian Gulf, the findings of this study may help enhance regional fishing strategies by promoting the integration of climate change considerations into operational planning.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105502"},"PeriodicalIF":2.3,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144312892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Brachyuran and anomuran Decapoda of the Emperor Seamounts","authors":"Evgeniia Egorova,&nbsp;Tatiana Dautova","doi":"10.1016/j.dsr2.2025.105501","DOIUrl":"10.1016/j.dsr2.2025.105501","url":null,"abstract":"<div><div>The bathyal areas in the Emperor Seamount Chain (North Pacific) were investigated during two expeditions of the RV <em>Akademik M.A. Lavrentyev</em> in 2019 and 2021. Over 60 crustacean specimens, including true crabs, king crabs, and squat lobsters, were collected and more than 70 h of video data recorded. We present first information on the composition and distribution of deep-sea decapods (Brachyura and Anomura) of the Emperor Chain obtained with a remote operated vehicle. First data on the squat lobster (Chirostyloidea, Galatheoidea) fauna from the Emperor Seamounts are provided. The known geographic range of <em>Macroregonia macrochira</em> is broadened. The depth range of <em>Chaceon imperialis</em> was expanded and found to be bimodal. We have identified a species of king crab (<em>Neolithodes bronwynae</em>) previously unknown in the North Pacific. Overall, the diversity in the Emperor Seamount Chain region shows a relatively high level of endemism and a presence of species previously known from distant regions, suggesting that further biogeographical studies of the region and surrounding areas may elucidate migration routes.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105501"},"PeriodicalIF":2.3,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of oceanographic characteristics and water mass exchange in the Persian Gulf and Gulf of Oman","authors":"Siamak Jamshidi,&nbsp;Samad Hamzei","doi":"10.1016/j.dsr2.2025.105503","DOIUrl":"10.1016/j.dsr2.2025.105503","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Physical oceanography of the Persian Gulf (PG), Strait of Hormuz (SH), and Gulf of Oman (GO) waters is poorly understood, necessitating more extensive and long-term studies. The main goal of this research is to comprehend the oceanographic properties and water mass exchange in this region. The study evaluates the range and patterns of the changes in physical characteristics (salinity (S), temperature (T), and depth (D or pressure, P)) and structure, mixing and stratification, and circulation of water in the PG, SH and GO. The findings revealed that the maximum recorded sea surface temperature in the PG exceeded than that in the GO during the summer. Seawater temperature in the PG decreased from east to west in the winter. The maximum sound speed values were in the surface layer during the summer (approximately 1557.5 m/s). The maximum salinity gradient and winter halocline were found between depths of 40 and 60 m. The vertical structure of seawater indicates the formation of strong thermal and density stratifications in the summer. The Richardson Number (R&lt;sub&gt;i&lt;/sub&gt; No.) in the SH ranged from &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mn&gt;0.5&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/msub&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mi&gt;o&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;0.65&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in the summer and it varied between &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mn&gt;0.03&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/msub&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mi&gt;o&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;0.15&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; during the winter. A dense water mass with a salinity more than 40 psμ (originating from the PG) was found below 150 m depth in the southwestern part of the GO. The stability and layering of the water column in the SH are under effect of the two-layer currents and the movement of water masses between the PG and GO. The static stability number (E) of the water column in the eastern part of the PG varied in the range of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;E&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; during the winter, and between &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;12&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;E&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;16&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in the summer. The maximum amount of the density anomaly occurs in the deep areas of the PG during the summer. During the winter, a two-layered water structure forms in the central areas of the SH. Horizontal and vertical gradients of the salinity and density facilitate the exchange of water masses between the PG and the GO through the SH. The average flushing time (Residence Time, T&lt;sub&gt;Residence&lt;/sub&gt;) of the PG is 1.82 years. The findings of the study offer an observational evaluation of the water mass exchange, seawater parameters, stratification, ","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105503"},"PeriodicalIF":2.3,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144510991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New insights in benthic biodiversity of the saya de Malha Bank","authors":"L. Corbari ,&nbsp;P. Bouchet ,&nbsp;L. Le Gall ,&nbsp;S. Hourdez ,&nbsp;I. Frutos ,&nbsp;B. Gouillieux ,&nbsp;E. Vassard ,&nbsp;G. Moutardier ,&nbsp;W.-J. Chen ,&nbsp;S.-L. Ng ,&nbsp;R. Bhagooli ,&nbsp;S. Ramah ,&nbsp;D. Kaullysing ,&nbsp;V. Munbodhe ,&nbsp;C. Labonte ,&nbsp;R. Boone ,&nbsp;S. Bender","doi":"10.1016/j.dsr2.2025.105500","DOIUrl":"10.1016/j.dsr2.2025.105500","url":null,"abstract":"<div><div>In the South West Indian Ocean, a unique, remote and atypical geomorphological structure, the Saya de Malha Bank, is considered as an underwater 'island' that plays a key role in understanding benthic biodiversity and connectivity processes in the Indian Ocean. In 2022, the Saya de Malha Bank has been explored during the Indian Ocean expedition led by Monaco Explorations. A team of the Muséum national d’Histoire Naturelle (Paris) and collaborators have explored the benthic diversity of the bank by deploying a combination of sampling methods, such as towed gears (dredge, trawl, and sledge) or by scuba-diving (on-sight, brushing and suction device samplings). A total of 81 stations have been sampled, comprising 35 shallow stations on the summit of the bank (19–58 m depth) and 46 stations gaining depth on the flanks of the bank (73–1141 m depth). From these sampling events, a large collection of marine invertebrates, fish and algae has been preserved for taxonomic (morphological and molecular) studies. The inventory of the benthic biodiversity of Saya de Malha is underway, but it is a long-term process. We propose here to focus on the most represented taxonomic groups (algae, molluscs, crustaceans, annelids and fish) by compiling the primary taxonomic data for the diversity metrics and highlighting some discoveries and potential species new to science. Although the inventory is far from complete, these first results emphasize the endemicity of the fauna and flora of the Saya de Malha Bank.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105500"},"PeriodicalIF":2.3,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144338555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diapycnal oxygen flux in the oxycline region of the core of the Arabian Sea Oxygen Minimum Zone","authors":"K. Ashin ,&nbsp;M.S. Girishkumar ,&nbsp;V.V.S.S. Sarma ,&nbsp;T.V.S. Udaya Bhaskar","doi":"10.1016/j.dsr2.2025.105499","DOIUrl":"10.1016/j.dsr2.2025.105499","url":null,"abstract":"<div><div>This study quantified the relative contributions of double diffusion and shear-driven mixing on the diapycnal oxygen flux in the oxycline region of the core of the Arabian Sea Oxygen Minimum Zone (OMZ), a critical oceanic region regulating the local ecosystem dynamics significantly. For that purpose, we used concurrent measurements of vertical profiles of dissolved oxygen and microstructure shear collected during the scientific cruise in May 2019. It was found that the presence of a moderately strong salt finger regime in the oxycline region enhanced the downward diapycnal oxygen flux (-7.0 ± 0.5x10^-2 μmol m^-2 s^-1) by an order of magnitude higher in contrast to traditionally considered shear-driven turbulence alone (-6.4 ± 0.7 x 10^-3 μmol m^-2 s^-1). This difference is solely attributable to the small magnitude of diapycnal diffusivity due to shear-driven turbulence (2.8 ± 1.1 x 10^-6 m² s^-1) compared to salt finger (10^-5 to 10^-4 m² s^-1). For the sake of comparison, the magnitude of lateral flux of oxygen due to horizontal circulation (3x10^-4 μmol m^-2 s^-1) and oxygen consumption rates due to biological processes estimated from observation (-3x10^-3 to -40 x 10^-3 μmol m^-2 s^-1) were much smaller than salt finger induced downward diapycnal oxygen flux in the oxycline region. As a result, there was a net downward oxygen flux from the oxycline into the OMZ. These findings highlighted the need to incorporate double diffusion processes in biogeochemical models to improve the accuracy of vertical oxygen distribution simulations in the Arabian Sea OMZ.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105499"},"PeriodicalIF":2.3,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144270946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the sensitivity of Optimum Multiparameter Analysis: a California Current System case study","authors":"Mercedes Pozo Buil ,&nbsp;Isaac Schroeder ,&nbsp;Steven J. Bograd ,&nbsp;Michael G. Jacox ,&nbsp;Elliott L. Hazen ,&nbsp;Dianne Deauna ,&nbsp;Emanuele Di Lorenzo ,&nbsp;Nicole S. Lovenduski ,&nbsp;Samuel Mogen ,&nbsp;Ryan R. Rykaczewski","doi":"10.1016/j.dsr2.2025.105498","DOIUrl":"10.1016/j.dsr2.2025.105498","url":null,"abstract":"<div><div>Eastern boundary upwelling systems, like the California Current System (CCS), represent a confluence and mixing of water masses whose variability and composition play a key role in modulating their high biological productivity and ecosystem variability. In the southern CCS, the relative contribution (i.e. proportion) and variability of its source water masses was quantified previously using an extended Optimum MultiParameter (eOMP) analysis, which is an inverse modeling technique that solves a set of linear mixing equations using quasi-conservative and non-conservative properties. However, there are several oceanographic decisions implicit in eOMP analysis that can generate uncertainties in the representation of the mixing and proportions of the source waters in a region. Here we quantify the sensitivity of these previous eOMP results in the southern CCS to varying oceanographic assumptions based on the uncertainty of the water mass properties, modified Redfield ratios, and alternate locations of the eastern tropical Pacific source waters. We show that the mean relative contributions of the main CCS source waters are more sensitive to the location of their selected source region (∼20–25 %) and the Redfield ratio (∼15–20 %) than to the uncertainty in the source water properties (∼2–5 %). Understanding the uncertainties of the eOMP assumptions benefits similar studies in other regions, especially in other eastern boundary upwelling systems (EBUS) where water masses characteristics and composition strongly impact the ecosystem.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105498"},"PeriodicalIF":2.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}