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

{"title":"Tortonian silicoflagellates from the offshore of northeast Indian Ocean","authors":"Lopamudra Roy ,&nbsp;Kevin McCartney ,&nbsp;Amit K. Ghosh ,&nbsp;Ajoy Kumar Bhaumik ,&nbsp;Sarajit Sensarma","doi":"10.1016/j.dsr2.2023.105297","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105297","url":null,"abstract":"<div><p><span>Analysis of the Tortonian sediments in the northeast Indian Ocean from NGHP–01–17A drilled at Andaman Basin shows 22 silicoflagellate taxa belonging to the genera </span><em>Bachmannocena, Dictyocha, Distephanopsis, Paramesocena</em> and <em>Stephanocha</em>. This study records the first evidence of Tortonian silicoflagellates from the offshore of northeast Indian Ocean. Two Partial Range zones namely <em>Dictyocha varia,</em> and <em>Dictyocha extensa</em> and one Subzone i.e. <em>Bachmannocena elliptica</em> have been proposed. In the present study, it has been observed that the transition of <em>D. varia</em> to <em>D. extensa</em><span> took place within the Tortonian. Fossil records of double skeletons in the silicoflagellate taxa are rare; however, we have documented double skeletons in three silicoflagellate taxa i.e. </span><span><em>Dictyocha calida, Dictyocha </em><em>fibula</em></span> subspecies <em>ausonia</em> and <em>Stephanocha speculum</em> (6-sided)<em>.</em> Ratio of <em>Dictyocha</em> and <em>Stephanocha</em> based on the combined abundance of all the taxa of the two genera reveals that there was substantial dominance of <em>Dictyocha</em> over <em>Stephanocha</em> throughout the studied sequence. The <em>Dictyocha/Stephanocha</em> palaeotemprature proxy indicated prevalence of warmer climate during the Tortonian (9.86 Ma to 7.39 Ma) with a cooling minimum in the <em>Bachmannocena elliptica</em> Subzone during 8.104 Ma – 8.088 Ma corresponding with nutrient rich condition.</p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"210 ","pages":"Article 105297"},"PeriodicalIF":3.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50194594","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":"Distinct patterns of coral lesion composition from national/quasi-national marine parks of Kerama and Yoron Islands, Ryukyu Archipelago","authors":"Dio Dirgantara,&nbsp;Mariyam Shidha Afzal,&nbsp;Takashi Nakamura","doi":"10.1016/j.dsr2.2023.105309","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105309","url":null,"abstract":"<div><p><span>A wide variety of coral communities are found in the Ryukyu Archipelago in southern Japan. Although reports of coral diseases and lesions in this region have increased since the 2000's, the variations of coral diseases among islands are somewhat limited. In this study, we conducted surveys to reveal the coral lesion assemblage and patterns in the marine national park area of Kerama Island and the quasi-national park on Yoron Island. Both sites are located 150 km away apart in the Ryukyu Archipelago. In total, 12 gross lesions were found in 30 coral genera. Corals in Yoron Island had 22% greater gross lesion abundance than Kerama Island (13.40 ± 1.36%) with an overall mean lesion abundance of 16.83 ± 1.66% (mean ± SE). Each Island shows a distinct pattern and group of coral lesion compositions. The disease lesion group of 7.21 ± 1.37% was dominated by White Syndrome (WS) and Black Band Disease (BBD), which severely infected various coral genera in Yoron Island. Corals in Kerama Island were predominantly affected by non-disease group lesion (9.76 ± 1.33%), such as </span><em>Chalinula nematifera</em> (CN) sponge overgrowing on the coral surface. Corals in the genus <em>Pachyseris</em> were highly susceptible (17.79%) to the diseases on Yoron Island, while Acroporid corals were the most susceptible (8.32%) to the diseases on Kerama Island. In addition, <span><em>Porites</em></span> were affected by disease and non-disease lesions from all sites in both Kerama and Yoron. These findings highlight the emergence of potential threats to coral communities in these national/quasi-national marine parks in Kerama and Yoron Island, which may be a factor limiting the survival and growth of key Scleractinian coral taxa. In addition, immediate consideration of environmental monitoring may be required to prevent coral disease outbreaks in the future.</p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"210 ","pages":"Article 105309"},"PeriodicalIF":3.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50194592","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":"Near-inertial oscillations in the deep Gulf of Mexico","authors":"Yingli Zhu,&nbsp;Xinfeng Liang","doi":"10.1016/j.dsr2.2023.105310","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105310","url":null,"abstract":"<div><p>Near-inertial oscillations (NIOs) are important for maintaining turbulent mixing that affects ocean circulation, biogeochemistry<span>, and climate. The spatial and temporal variability of NIOs in the deep part of the Gulf of Mexico<span> (GoM) has rarely been reported. In this study, a collection of moored current observations was used to examine the spatiotemporal variability of NIOs in the GoM. In the upper layer (0–800 m), a strong seasonal variability of NIOs appears in the eastern GoM with larger amplitudes in winter than in summer and is attributed to the seasonal variability of surface winds and mixed layer depth. In the bottom layer (within 400 m above the bottom), strong NIOs are found in the middle and eastern GoM and show weaker seasonal variability. While winds still matter for the seasonal variability of NIOs in the bottom layer in the eastern GoM, low-frequency flows generally play a more important role in regulating NIOs through interactions with topography, particularly on the continental slope.</span></span></p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"210 ","pages":"Article 105310"},"PeriodicalIF":3.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50194587","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":"Seeps and vents of the Bering Sea","authors":"Vladimir V. Mordukhovich,&nbsp;Elena M. Krylova,&nbsp;Paul R. Dando","doi":"10.1016/j.dsr2.2023.105290","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105290","url":null,"abstract":"","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105290"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174438","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":"Record-breaking 2020 summer marine heatwaves in the western North Pacific","authors":"Yulong Yao ,&nbsp;Chunzai Wang ,&nbsp;Chao Wang","doi":"10.1016/j.dsr2.2023.105288","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105288","url":null,"abstract":"<div><p><span><span>Record-breaking marine heatwaves (MHWs) occurred in the western North Pacific during the summer of 2020. These unprecedented MHWs were consistent with favorable large-scale conditions that are linked to an anomalous western North Pacific subtropical high (WNPSH), resulting mainly from sea surface temperature (SST) anomalies across the tropical oceans. In addition, a moderate La Niña-like pattern was also conducive to transporting warm seawater to the western North Pacific. Mixed-layer heat budgets suggest that surface heat flux contributed to the SST anomaly in the western subtropical Pacific. In contrast, oceanic heat </span>advection dominanted in the South China Sea and the western equatorial Pacific. Numerical model experiments indicated that the tropical Indian Ocean SST anomalies were responsible for the enhanced WNPSH. The increased zonal SST gradient across the tropical Pacific also played an important role. Inter-ocean interactions can modulate </span>climate variability<span><span> through ocean-atmospheric coupling and deserve more attention when predicting MHWs within the context of global warming. In addition, it is critical to consider MHWs as a powerful tool in detecting acute, intense thermal stress events in the </span>coral bleaching pre-warning system.</span></p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105288"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174423","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":"Cause and impact of Andaman Sea's salinity variability: A modeling study","authors":"Abhishek Pasula,&nbsp;Deepak N. Subramani","doi":"10.1016/j.dsr2.2023.105291","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105291","url":null,"abstract":"<div><p>The Andaman Sea is an important and strategic region for India, both from a security and conservation viewpoint. Documenting the spatiotemporal variability of salinity<span> is fundamental to understanding this region's dynamics. We studied the Andaman Sea's seasonal and inter-annual salinity variability during the Boreal summer (JJAS) using NEMO reanalysis data (1993–2018). Analysis of river influx, precipitation, Empirical Orthogonal Functions<span> of the salinity fields, numerical particle trajectory experiments, and statistical significance tests were conducted to understand the causal factors and impact of the Andaman Sea's salinity variability. Our study shows that it is the Southwest Monsoon Current (SMC) that brings a significant influx of salinity into the Andaman Sea and governs the seasonal cycle. We also document and explain the different surface and sub-surface dynamical trends. We show that higher salinity influx to the Andaman Sea is correlated with the strength of SMC. Crucially, this study is the first-ever attempt to comprehend the salinity dynamics of the Andaman Sea utilizing both Empirical Orthogonal Function (EOF) analysis and particle trajectories. We also note the reported reduction in shark catch and qualitatively analyze its relation to the seasonal salinity cycle, motivating the need for further physical-biological combined studies of the region.</span></span></p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105291"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174427","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":"Seasonal Indonesian Throughflow (ITF) across southern Java determines genetic connectivity of Sardinella lemuru (Bleeker, 1835)","authors":"A. Sartimbul ,&nbsp;V.A. Winata ,&nbsp;R.D. Kasitowati ,&nbsp;F. Iranawati ,&nbsp;E. Rohadi ,&nbsp;D. Yona ,&nbsp;U.G. Anjeli ,&nbsp;W.S. Pranowo ,&nbsp;F.M. Lauro","doi":"10.1016/j.dsr2.2023.105295","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105295","url":null,"abstract":"<div><p><em>Sardinella lemuru</em> populations are considered near-threatened in Bali Strait. Despite declining fish stock, documented landings of <em>S. lemuru</em> at the Prigi waters unexpectedly climbed during the 2nd transitional inter-monsoon season of 2019. Here we used a combination of molecular taxonomy and morphometrics-meristics to determine the genetic link between <em>S. lemuru</em> populations in East Java's southern seas (Prigi and Puger) and those in the Philippines. The results of both molecular and morphometric-meristic analyses suggest that extensive genetic mixing between the populations from Prigi and the Philippines is occurring. Most samples clustered with the <em>S. lemuru</em> populations from the Philippines in Clade-1 and Haplogroup A and B implied high genetic connectivity. The inferred patterns of haplotype network and haplogroup relative frequency indicate the dispersal, genetic homogeneity, and absence of geographical barriers between <em>S. lemuru</em> populations were also supported by a seasonal model of ocean circulation: during the southeast monsoon, greater Indonesian Through-Flow and South Java Current, followed by westward currents along Java's south coast. The findings of this study give much-needed evidence that <em>S. lemuru</em><span> populations disperse to a secondary fishing area (in Prigi waters), followed by high plankton abundance in 2019, as a result of ITF<span> and local seasonal circulation. The unique sequences of Puger-2017 and the remainder of Prigi-2017 in Clade-2 with overall moderate genetic distance separated from Clade-1 because the Puger water mass are influenced by the Java Sea and Madura Strait or possibly migrated from their habitats in the western part of Indonesia or the Java Sea.</span></span></p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105295"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174439","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":"Vertical imbalance in organic carbon budgets is indicative of a missing vertical transfer during a phytoplankton bloom near South Georgia (COMICS)","authors":"S.L.C. Giering ,&nbsp;R. Sanders ,&nbsp;S. Blackbird ,&nbsp;N. Briggs ,&nbsp;F. Carvalho ,&nbsp;H. East ,&nbsp;B. Espinola ,&nbsp;S.A. Henson ,&nbsp;K. Kiriakoulakis ,&nbsp;M.H. Iversen ,&nbsp;R.S. Lampitt ,&nbsp;K. Pabortsava ,&nbsp;C. Pebody ,&nbsp;K. Peel ,&nbsp;C. Preece ,&nbsp;K. Saw ,&nbsp;M. Villa-Alfageme ,&nbsp;G.A. Wolff","doi":"10.1016/j.dsr2.2023.105277","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105277","url":null,"abstract":"<div><p>The biological carbon pump, driven principally by the surface production of sinking organic matter and its subsequent remineralization to carbon dioxide (CO₂) in the deep ocean, maintains atmospheric CO₂ concentrations around 200 ppm lower than they would be if the ocean were abiotic. One important driver of the magnitude of this effect is the depth to which organic matter sinks before it is remineralised, a parameter we have limited confidence in measuring given the difficulty involved in balancing sources and sinks in the ocean's interior. One solution to this imbalance might be a temporal offset in which organic carbon accumulates in the mesopelagic zone (100–1000 m depth) early in the productive season before it is consumed later. Here, we develop a novel accounting method to address non-steady state conditions by estimating fluxes of particulate organic matter into, and accumulation within, distinct vertical layers in the mesopelagic zone using high-resolution spatiotemporal vertical profiles. We apply this approach to a time series of measurements made during the declining phase of a large diatom bloom in a low-circulation region of the Southern Ocean downstream of South Georgia. Our data show that the major export event led to a significant accumulation of organic matter in the upper mesopelagic zone (100–200 m depth) which declined over the following weeks, implying that temporal offsets need to be considered when compiling budgets. However, even when accounting for this accumulation, a mismatch in the vertically resolved organic carbon budget remained, implying that there are likely widespread processes that we do not yet understand that redistribute material vertically within the mesopelagic zone.</p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105277"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174485","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":"Atmospheric and advective forcing of upwelling on South Africa's central Agulhas Bank","authors":"Lisa Hancke ,&nbsp;David Smeed ,&nbsp;Mike Roberts ,&nbsp;Cristina Russo ,&nbsp;Darren Rayner ,&nbsp;Fatma Jebri","doi":"10.1016/j.dsr2.2023.105293","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105293","url":null,"abstract":"<div><p>Current and temperature structures on South Africa's central Agulhas Bank are described from six months of moored observations and ancillary data collected during the seasonal transition from austral spring to summer (October 2018–March 2019). The occurrence of an intermittend mid-shelf upwelling ridge, associated with increased productivity, is an important part of the shelf's thermal structure. However, the subsurface evolution of this cold ridge has not been documented to date. A mooring array that transected the wide central shelf captured the seasonal increase in stratification that culminated in the formation of a cold ridge in late summer. We show that the cold ridge originates in the wind-driven upwelling zone on the eastern Agulhas Bank and emphasise the importance of oceanic forcing in maintaining the subsurface thermal structure through advective steering of wind-driven coastal upwelling plumes and through dynamic shelf edge upwelling. The main source of the cold basal layer at the mooring transect originated from upwelling further east, but persistent near-seabed temperatures &lt;9 °C on the outer shelf during the encroachment of the Agulhas Current confirm the contribution of shelf edge upwelling, offshore of the mooring transect, to the cold bottom layer on the Agulhas Bank. Of particular interest is the strengthening of the south-westward shelf current, inshore of cyclonic flow in the Agulhas Bight that accelerated the offshore advection of productive coastal water in the shape of the cold ridge. We show the shelf circulation to be highly coherent across and along the shelf. Shelf-wide barotropic pulses were driven by increased zonal wind stress that was in turn associated with variation in coastal sea level. In the light of global climate change, this work highlights the importance of long term in-situ monitoring in understanding ecosystem functioning on the highly dynamic Agulhas Bank.</p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105293"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174426","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":"Causal relations between the loop current penetration and the inflow/outflow conditions inferred with a rigorous quantitative causality analysis","authors":"Yang Yang ,&nbsp;Guanqi Fu ,&nbsp;X. San Liang ,&nbsp;Robert H. Weisberg ,&nbsp;Yonggang Liu","doi":"10.1016/j.dsr2.2023.105298","DOIUrl":"https://doi.org/10.1016/j.dsr2.2023.105298","url":null,"abstract":"<div><p>The causal relationship between the Loop Current (LC) penetration into the Gulf of Mexico and the inflow/outflow conditions in the Yucatan Channel and the Straits of Florida is analyzed using a recently developed causality analysis, which is quantitative in nature, and rigorously derived from first principles. Long-term time series from a 23-year high-resolution reanalysis product reveals that the LC penetration is associated with a dipole (tripole) mode of transport (vorticity flux) in both channels. These relationships, though significant from a perspective of correlation, do not necessarily imply causality. By applying the causality analysis, we identify a clear asymmetry of causality, that is, the flow conditions in the Yucatan Channel and the Straits of Florida can both cause the LC penetration. Conversely, the LC path state is less causal to the current variability in the two channels. The spatial causal structures further reveal that the upstream influence from the Yucatan Channel is strong in the main body of the LC as well as its extension area, while the downstream influence from the Straits of Florida is confined within the eastern branch of the LC. The asymmetric causal relations obtained from the data-assimilative reanalysis product are further confirmed in a free-running model simulation forced by three repeated cycles of atmospheric forcing, although the strength of the causality could vary from one simulation cycle to another, due to the intrinsic variability of the LC system.</p></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"209 ","pages":"Article 105298"},"PeriodicalIF":3.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50174424","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}