Changes In Marine Environment Research Articles

Isotopic constraints on the late Pleistocene glacial water and sediment inputs to the central Arctic ocean

The Quaternary history of the Arctic Ocean reflects pronounced periodic changes in marine and glacial environments. This variability is an important component of the Arctic paleoclimatic system. For more insight, we use isotopic measurements on the detrital (Nd-Sr-Pb) and authigenic (Nd) phases of the Quaternary sediments from the central Arctic Ocean. We analyze core ICE4 from ∼3 km water depth off the Lomonosov Ridge. This core was previously studied for other sedimentary proxies (Dong et al., 2022). The analyzed record is estimated to cover major Late Pleistocene Weichselian/Wisconsinian glaciations occurring over the last ∼100–200 ka. Our results provide new evidence that glacially-derived waters from the glaciated margins reached the bottom of the deep Arctic basins. We infer that these waters were delivered to the deep basins by hyperpycnal flows originating from subglacial outbursts accompanying overflow meltwater and iceberg discharge during glacial/deglacial events. Voluminous outbursts during the older, presumed Early/Middle Weichselian glaciation, ca. 115-35 ka, are traced to the West Siberian margin impacted by the Eurasian Ice Sheet. Similar sedimentary layers are found in longer records from the central Arctic Ocean at older stratigraphic intervals. Sediments constrained to the Last Glacial Maximum have less pronounced glacigenic inputs with a stronger Laurentide Ice Sheet signature. The circulation patterns were likely dependent on the interplay of the timing and extent of the Laurentide and Eurasian ice sheets.

Mass capture fishing in the Marquesas Islands

ABSTRACTMass capture of small fishes with a variety of nets, traps, and weirs was widely practiced and economically important across East Polynesia at western contact. Archaeological research, however, has suggested these technologies were less important during the early settlement period and gained prominence over time. Several explanations have been proposed, including resource depression, changes in marine environments, and/or social and economic reorientations. In the Marquesas Islands, pelagic and offshore fishes were historically well represented in early assemblages relative to most Polynesian islands. Here we report on fishbone assemblages from Nuku Hiva Island that were recovered with fine mesh screens, identified using a wide range of skeletal elements, and analysed with morphometric methods. The Hakaea Beach results demonstrate that mass capture of small fishes was especially important at this locality and sustained over three early, successive occupations. These patterns may reflect the nature of the local fisheries, preferential use of high‐return capture strategies in this reef‐limited setting, and/or purposeful avoidance of ciguatera‐prone fishes and a preference for less vulnerable fishes. Overall, our findings highlight geographic variation in early Marquesan fisheries and provide archaeological evidence that mass capture technologies had an important place in the maritime toolkits of the earliest East Polynesian fishers.

A spatiotemporal attention-augmented ConvLSTM model for ocean remote sensing reflectance prediction

Remote sensing reflectance (Rrs) is an essential parameter in ocean color remote sensing and a fundamental input for the estimation of ocean color elements. Predicting Rrs has the potential to enable simultaneous prediction of multiple marine environmental parameters, facilitating multi-perspective analysis of marine environmental changes. This paper proposes a spatiotemporal attention-augmented ConvLSTM-based model for ocean Rrs prediction. The developed model can predict Rrs for up to seven days by simultaneously learning spatiotemporal features from time series Rrs and auxiliary environmental variables. According to the experiments, the proposed model achieves optimal performances on Rrs predictions at 443, 488, and 555 nm, with Root Mean Squared Error (RMSE) and Mean Absolute Percentage Error (MAPE) for the first four prediction days less than 5.6*10-4 sr-1 and 8.6 %, respectively, which are better than the performance of the convolutional neural network (CNN), the LSTM, CNN-LSTM, and the ConvLSTM. The spatial and temporal variations of Rrs are also compared to evaluate the effectiveness of the model, presenting a consistent spatiotemporal pattern between predicted and observed Rrs. We also found that integrating sea surface temperature (SST), photosynthetically available radiation (PAR), and aerosol optical thickness at 869 nm (AOT869) into the model can improve the prediction accuracy in various degrees. This work suggests the proposed deep learning model can predict Rrs for 7 days with a convincing performance, providing critical data and technical support for ocean-related applications, such as algae bloom monitoring.

Transformative Ecological and Human Impacts from Diminished Sea Ice in the Northern Bering Sea

Abstract Our goal is to tie climate-scale meteorology to regional physics and ecosystem changes and demonstrate a few resulting impacts to which regional peoples are having to respond in the Alaskan Bering Strait region. The sea ice loss events in the winters of 2017/18 and 2018/19 initiated a series of marine environmental, ecological, and industrial changes through a chain of connected events from jet-stream meanders, storms, southerly winds, warmer sea temperatures, and minimum sea ice cover. Resulting impacts continue as coastal communities respond to ongoing nutritional, cultural, and economic challenges. Global warming potentially initiated these events through a weakened atmospheric Arctic Front. Ecological shifts included a transition/reorganization of the Bering Strait regional marine ecosystem. Subsequent changes included shifts in zooplankton species, increases in large-bodied, predatory fish species moving northward, an ice seal unusual mortality event, and seven consecutive years of multispecies seabird die-offs. These changes in the marine ecosystem create a serious food security concern. Ongoing impacts include large, toxic harmful algal blooms and coastal erosion. Recent changes to the maritime industries of the transboundary waters of the Bering Strait include increased industrial ship traffic, planned development of the Port of Nome, and northward proximity of foreign fishing activity. Projections for the next decades are for an increasing frequency of low sea ice years and continuing ecosystem and industrial transitions that contribute to increasing economic and food security concerns for the 16 coastal communities that compose the Bering Strait region. Significance Statement Extreme events in the atmosphere/oceans and resultant record sea ice minimums in 2018 and 2019 were manifested in marine ecosystem transitions and maritime industry impacts. This led to ongoing concerns over the food safety and food security of marine resources essential to the nutritional, cultural, and economic well-being of Alaskan coastal communities of the Bering Strait region. Persistent weakening of the Arctic Front may signal an increased frequency of low sea ice events into the next decades.

More Frequent Abrupt Marine Environmental Changes Expected

AbstractWe quantify an elevated occurrence of abrupt changes in ocean environmental conditions under human‐induced climate forcing using Earth system model output through a novel analysis method that compares the temporal evolution of the forcings applied with the development of local ocean state changes for temperature, oxygen concentration, and carbonate ion concentration. Through a multi‐centennial Earth system model experiment, we show that such an increase is not fully reversible after excess greenhouse gas emissions go back to zero. The increase in occurrence of regional abrupt changes in marine environmental conditions has not yet been accounted for adequately in climate impact analyses that usually associate ecosystem shifts large‐scale variability or extreme events. Estimates for remaining greenhouse gas emission targets need thus to be more conservative.

Geochemical insights into secular changes in the depositional environment of ferromanganese nodules in the western North Pacific

Understanding Earth's surface dynamics and biological evolution requires deciphering past marine environmental changes. Hydrogenetic ferromanganese nodules formed by the direct precipitation of Fe–Mn oxide/hydroxide from seawater could record the marine environment at the time of deposition, as in the case of ferromanganese crusts. In this study, petrological and geochemical analyses were conducted on ferromanganese nodules collected from the Japanese Exclusive Economic Zone around Minamitorishima Island in the western North Pacific Ocean. Additionally, the results were compared with those of ferromanganese crusts distributed in the same area to elucidate the secular changes in the depositional environment. The mineralogical features (consisting solely of Fe-vernadite with an absence of 10 Å Mn oxide) and the geochemical characteristics (including positive Ce-anomaly and negative Y-anomaly in rare-earth element patterns, high Co contents, and low Cu and Ni contents) of the nodules suggest that the studied nodules are of a hydrogenetic origin. From the inside to the outside of the nodule, the Mn/Fe and Y/Ho ratios decrease while the Th/U ratio increases, indicating a changing depositional environment over time. A similar trend was observed in ferromanganese crusts from the nearby Takuyo-Daigo Seamount. Furthermore, similar compositional changes were observed on the surfaces of the crust samples (uppermost 1–3 mm), which correlated with depth-related changes in seawater oxygen concentrations. Therefore, the observed cross-sectional changes in the chemical compositions of the nodules and crusts may reflect changes in seawater-dissolved oxygen concentrations over time. The Mn/Fe and Y/Ho trends indicate a shift towards a less oxic environment with increasing age while maintaining the current depth profile, implying an expansion of the oxygen minimum zone (OMZ). Moreover, the observed Ni and Cu enrichment, together with the changes in the Mn/Fe and Y/Ho ratios, suggest that the expansion of the OMZ was caused by increased surface ocean productivity.

Redox geochemical signatures in Mediterranean sapropels: Implications to constrain deoxygenation dynamics in deep-marine settings

Global warming and anthropogenic activity are boosting marine deoxygenation in many regions around the globe. Deoxygenation is a critical ocean stressor with profound implications for marine ecosystems and biogeochemical cycles. Understanding the dynamics and evolution of past deoxygenation events can enhance our knowledge of present-day and future impacts of climate change and anthropogenic pressure on marine environments. Many studies have reconstructed the evolution redox conditions of past deoxygenation events using geochemical proxies. In this regard, the present work focuses on understanding the paleoenvironmental significance of geochemical redox signals derived from the onset, evolution and termination of regional-scale deoxygenations in deep-marine settings, with a specific focus on sapropels in the Eastern Mediterranean (EM). Sapropels, rhythmic organic-rich sediments deposited in EM, offer a unique opportunity to investigate recent deoxygenation events linked to past climate changes. Sapropels serve as paleo-archives of past deoxygenation events and can provide insights into the potential impacts of ongoing climate change on marine ecosystems and biogeochemical cycles. By integrating previous sapropel geochemical studies with a detailed analysis of new geochemical data from five Quaternary sapropels (S1, S5, S6, S7 and S8) in three different EM deep-marine settings, this study enhances our understanding of the paleoenvironmental significance of geochemical redox signals produced by deoxygenation dynamics and postdepositional processes in different deep-marine settings. The study supports that certain trace elements, such as Mo, V, U, Co, and Ni, are identified as more reliable redox proxies compared to Cr, Cu, Pb, and Zn. Four recurrent geochemical intervals attributed to specific redox conditions and postdepositional processes have been identified. Moreover, internal calibration of redox proxies thresholds has been performed and demonstrates how local environmental conditions (e.g., productivity rate) and hydrogeographic features (e.g., water-depth, particulate-shuttling intensity, deep-water renewal and fluvial input) play crucial roles in controlling the authigenic uptake rates of redox-sensitive trace metals, and subsequently, redox thresholds values of geochemical redox proxies. The results also emphasize the importance of postdepositional processes to accurately interpret geochemical signals in paleoenvironmental studies. This research enhances our overall understanding of geochemical signals associated with regional-scale deoxygenation events in deep-marine settings, offering new insights into predicting biogeochemical changes in marine environments undergoing a transition towards anoxia. By comprehending the dynamics of past and present deoxygenation, we acquire valuable knowledge regarding the potential effects of climate variability in marine ecosystems.

Reconstruction of dissolved oxygen in the Indian Ocean from 1980 to 2019 based on machine learning techniques

Oceanic dissolved oxygen (DO) decline in the Indian Ocean has profound implications for Earth’s climate and human habitation in Eurasia and Africa. Owing to sparse observations, there is little research on DO variations, regional comparisons, and its relationship with marine environmental changes in the entire Indian Ocean. In this study, we applied different machine learning algorithms to fit regression models between measured DO, ocean reanalysis physical variables, and spatiotemporal variables. We utilized the Extremely Randomized Trees (ERT) model with the best performance, inputting complete reanalysis data and spatiotemporal information to reconstruct a four-dimensional DO dataset of the Indian Ocean during 1980–2019. The evaluation results showed that the ERT-based DO dataset was superior to the DO simulations in Earth System Models across different time and space. Furthermore, we assessed the spatiotemporal variations in reconstructed DO dataset. DO decline and oxygen-minimum zone (OMZ) expansion were prominent in the Arabian Sea, Bay of Bengal, and Equatorial Indian Ocean. Through correlation analysis, we found that temperature and salinity changes related to solubility primarily control the oxygen decrease in the middle and deep sea. However, the complicated factors with solubility change, vertical mixing, and circulation govern the oxygen increase in the upper and middle sea. Finally, we conducted a volume integral to estimate the oxygen content in the Indian Ocean. Overall, a deoxygenation trend of −141.5 ± 15.1 Tmol dec−1 was estimated over four decades, with a slowdown trend of −68.9 ± 31.3 Tmol dec−1 after 2000. Under global warming and climate change, OMZ expanding and deoxygenation in the Indian Ocean are gradually mitigating. This study enhances our understanding of DO dynamics of the Indian Ocean in response to deoxygenation.

Fifty-year study of microplastics ingested by brachyuran and fish larvae in the central English North Sea

Microplastics (MPs) are ubiquitous pollutants in marine environments. Among the many detrimental consequences of microplastic pollution, its consumption by marine biota is of particular relevance for human health, due to exposure through the food web. Long-term time-series biotic samples are overlooked sources of information for microplastics research. These collections are extremely valuable for the detection and monitoring of changes in marine environments. However, there are very few long-term studies (>10 years) of the uptake of microplastics by biota. Here, we used Dove Time Series planktonic samples (from 1971 to 2020) to assess the presence and prevalence of microplastics in the English North Sea coast over time. Fish and brachyuran larvae were selected due to their commercial importance and consequent implications for human health. A custom enzymatic digestion method was used to extract microplastics for FTIR-ATR polymer identification. An increasing cumulative trend in MP ingestion was identified. Cellophane and polyethylene terephthalate were the polymer types found most frequently in both taxa. Although a total higher microplastics uptake was observed in fish, consumption was not significantly different between taxa over time. Equally, results were not clearly related to microplastics shape or polymer type. This work did not find significant long-term evidence on the increasing uptake of microplastic particles by zooplankton over time. However, the results of this report identified additives, plasticisers, and other more complex and hazardous compounds that should not be released to the environment (e.g., bis-(2-hydroxyethyl) dimerate, propylene glycol ricinoleate) inside marine biota. The study detailed herein provides a case study for the use of long-term time-series in providing accurate assessments of microplastic pollution in marine biota.

Suspended Sediment Concentration Estimation along Turbid Water Outflow Using a Multispectral Camera on an Unmanned Aerial Vehicle

Optical remote sensing using unmanned aerial vehicles (UAVs) is proposed to monitor changes in marine environments effectively. Optical measurements were performed using a UAV multispectral camera (RedEdge, five spectral wavelengths of 475, 560, 668, 717, and 842 nm) with high spatial (5 cm) and temporal (1 s) resolutions to monitor the rapidly changing suspended sediment concentration (SSC) in the Saemangeum coastal area on the western coast of Korea. To develop the SSC algorithm, optical field, and water sample measurements were obtained from outside (11 stations) and inside (three stations) regions separated by a seawall, accounting for 100 measurements from 2018 to 2020. Accordingly, the remote sensing reflectance (Rrs) was estimated at each sampling station and used to develop the SSC algorithm based on multiple linear regression. The algorithm reasonably estimated the SSC with an R2 and root mean square error of 0.83 and 4.27 (mg L−1), respectively. Continuous individual UAV measurements over the coastal area of Saemangeum were combined to generate a wider SSC map. For the UAV observational data, the atmospheric influence at each altitude was reduced to the surface altitude level using a relative atmospheric correction technique. The SSC map enabled front monitoring of SSC fluctuations caused by discharge water due to the sluice gate opening. These results demonstrated the usability of the UAV-based SSC algorithm and confirmed the possibility of monitoring rapid SSC fluctuations.

Change of marine redox environment in the western Okinawa Trough since the mid-Holocene: Evidence based on geochemical records

The marine redox environment (MRE) plays a crucial role in the conversion and preservation of seafloor material and is a significant factor in the ocean carbon cycle. The evolution and driving mechanism of MRE are complex and present distinct regional characteristics over different time scales. The Okinawa Trough, situated in the East Asian monsoon realm, is influenced by the Kuroshio Current and flushing water, and its closed geographical pattern and multiple environmental factors make it highly sensitive to climate and marine environment changes. In this study, sediment samples from core GHN056–09 retrieved in the western Okinawa Trough were analyzed to investigate the high-resolution evolution of MRE since the mid-Holocene. The concentration of redox-sensitive elements (V, Co, Ni) and total organic carbon (TOC) were measured. Co/Ni and V/(V+Ni) values in the sediment samples indicated predominantly oxic conditions with matching productivity levels indicated by TOC (in the range of 0.28–1.17%). The oxic condition decreased during 6500–1500 a BP, and a strengthening trend was identified from 1500 a BP to present. By comparing these records with climate and environmental records, we found that weaker El Niño-Southern Oscillation (ENSO) and northward position of Intertropical Convergence Zone (ITCZ) resulted in less monsoon precipitation into the Okinawa Trough. Thinner freshwater lids could enhance seawater mixing at different layers, leading to strong oxic conditions. In contrast, stronger ENSO and southward position of ITCZ controlled by stronger solar insolation supplied more freshwater into the Okinawa Trough. Thicker freshwater barriers blocked the exchange of seawater from bottom to surface, resulting in weak oxic conditions. The trace element records in this study provide robust evidence on the high-resolution variability of MRE driven by the frequency of ENSO, movement of ITCZ, and changes in regional precipitation. Our findings offer new insights into the evolution of MRE in response to global and local climate changes.

Petrography and geochemistry of the Permian-Triassic boundary interval, Kangjiaping section, South China: Implication for the drastic marine environment change

The Permian-Triassic transitional interval exposed well at Kangjiaping section, northwestern Hunan, South China, contains microbialites, oolitic and oncolitic limestones intercalated with vermiculate micritic limestones in the Lower Triassic overlying the uppermost Permian bioclastic limestones, which provides an excellent opportunity to study the environmental changes after the end-Permian mass extinction (EPME) and the origins and environmental significance of these various anomalous sediments. In this paper, we describe in detail the petrographic and geochemical characteristics of these anomalous sediments, together with the reconstruction of the marine environment after the EPME. The continental margin weathering was significantly enhanced after the EPME, indicated by the higher concentrations of terrigenous minerals, Th, Sc, Sr, and rare earth elements in the Lower Triassic carbonates than in the uppermost Permian bioclastic limestones. Indicators such as V/(V + Ni) and Ni/Co ratios suggest that the oxygen content of shallow seawater significantly decreased after the EPME. While, most samples from the Kangjiaping section preserve a negative cerium anomaly, indicating the shallow seawater was still oxygenated both before and after the EPME. In addition, the abnormally rapid carbonate precipitation rate indicates a supersaturation state with respect to calcium carbonate in the shallow seawater after the EPME, but the depth and salinity of seawater and climate indicated by different microfacies are still different. Under the setting of a rapid transgression after the EPME, the microbialites first deposited on the platform with the exclusion of grazers at the beginning of the Early Triassic, followed by the oncolites formed when the climate turned humid with a relative sea-level rise. The oolites were primarily deposited in an arid climate with a relative sea-level fall, and the salinity and hydrodynamics of seawater controlled the ooids’ grain sizes. In contrast, the (vermiculate) micritic limestones were mainly formed in a humid climate with a relative sea-level rising and more terrigenous inputs. Therefore, the periodic relative sea-level fluctuation and arid-humid climate alternations play a vital role in the evolution and repeat stacking of various microfacies in the Kangjiaping section.

Multi-proxy evidence of unprecedented hydroclimatic change in a high Arctic proglacial lake: Linnévatnet, Svalbard

ABSTRACT Svalbard is at the forefront of sea ice, marine, and terrestrial environmental change in the Arctic and so can be viewed as an example of what may be expected in other high latitude regions influenced by the North Atlantic Current. However, there are few highly resolved (subdecadal) paleoclimate records from this area that provide a long-term perspective on recent climatic changes. Here, we investigate a new composite sedimentary sequence from Linnévatnet, western Spitsbergen, spanning the last ~2,000 years. The chronology of this new composite laminated sequence is supported by four radiometric dates. Prior to conducting paleoclimate investigations on these lake sediments, we investigated the sediment sources entering Linnévatnet. Sediment samples collected around the lake’s watershed indicate that the main sediment sources come from the eastern carbonate valley wall as well as Linnéelva, the main river system. Micro-X-ray fluorescence (µ-XRF) results indicate that calcium is the largest component of sediment delivered to the delta-proximal basin, where the sedimentary record was collected. Percentage organics deduced from loss-on-ignition measurements reveal an antiphased relationship with calcium and magnetic susceptibility, implying that the sediment loading at the core site is largely modulated by the alternation of calcium derived from carbonates of the eastern flanks of the valley and by coal-bearing sandstone from Linnéelva, derived from the main river inflow that drains the central valley. Linnéelva is mainly fed by snow and glacier meltwaters from Linnébreen, the small valley glacier now located 7 km south of Linnévatnet. Because Linnébreen is underlain by coal-bearing sandstone, organic content in Linnévatnet lake sediments can be used as an indicator of glacier activity. Annually resolved parameters—that is, calcium and grain size—were found to be strongly correlated to temperature inferred from nearby Lomonosovfonna δ18O ice record as well as the wider reconstructed Northern Hemisphere winter temperature. The coarsest grain size, highest calcium values, and lowest concentration of organics occurred just in recent years, suggesting that glacier influence on the sedimentary input to Linnévatnet is now at an all-time low in the context of the past millennia.

Disclosure of the sustainable development goals in the maritime industry and port sector

The maritime industry and port sector are catalysts of economic growth and development of countries. However, they can generate significant environmental and social impacts on marine ecosystems and neighbouring communities. The sustainable development goals (SDGs) proposed by the United Nations (UN) make up the 2030 Agenda and suggest a global sustainable development that needs the collaboration of various stakeholders. In this context, the article aims to identify the SDGs most evidenced in the maritime industry and port sector from a systematic literature review using the tools EndNote, IRaMuTeQ and VOSviewer. The results pointed to SDG 9 Industry, Innovation and Infrastructure, 13 Action against Climate Change and 14 Life on the Water as the most addressed by the studies, highlighting the guidance of the maritime industry and the port sector in contributing to sustainable development based on concern for the marine environment and climate change. It was observed that the studies identified the relevance of contributing to the SDGs. On the other hand, the practical applications were not properly described, thus making it difficult to understand the priority actions for an effective contribution to the SDGs.

Spatiotemporal changes and influencing factors of water clarity in the Yellow Sea over the past 20 years

Water transparency is an important parameter for describing the optical properties of water. It reflects changes in marine environment and is of great significance for guiding the development and protection of marine environment. In this study, based on the algorithm proposed by Lee et al. in 2015, water transparency in the Yellow Sea from 2003 to 2022 was inverted. The results revealed that, in terms of spatial distribution, the water in western region of the Yellow Sea had relatively low transparency, whereas the water in the central and southern regions had high transparency. Regarding temporal trends, declining transparency was observed throughout most of the study period, but the trends reversed and transparency began to increase in 2017. Empirical orthogonal function analysis confirmed that water transparency was primarily influenced by the optical constituents of water. Long-term monitoring of water clarity is of significant importance for the preservation of marine ecological environments.

Using multiple linear regression for estimating total mussel (Mytilus californianus) shell size to accommodate morphological variability related to diverse environments

Understanding variation in mollusk shell size through time can be useful for interpreting changes in past marine environments and human behavior related to subsistence. Recent studies have provided means to estimate total shell length for California mussel (Mytilus californianus) by using a single morphological measurement in a simple linear regression approach; however, shell morphology may differ between environmentally diverse areas and through time, in turn potentially influencing the reliability of single variable models generated from measurements of shells harvested from a different geographic region to predict total shell length for archaeological samples. In this study, we examined the performance of models built from three site specific samples from contemporary mussel beds from Santa Rosa Island, southern California and models built from a pooled sample. The data was split into training (80%) and testing (20%) subsets to construct and validate eight multivariable models using a best subset regression approach. We then examined the performance of our models on each subset, evaluating measures of bias, accuracy, coverage, and precision. We also evaluated the performance of our models using an archaeological sample (CA-SRI-138) as an additional external validation sample. For each sample, we consider a model with all measurements and a model using only those measurements likely observed in fragmentary assemblages. We also developed single variable models for comparison to the performance of multivariable models. Multivariable models consistently demonstrate better performance than single variable models. The models using the pooled sample were also more accurate, precise, and exhibited less bias than the site-specific models. Each site-specific model selected a different subset of variables and indicated a range of variable importance, which is captured in the increased generalizability of the multivariable, pooled sample models when estimating total shell length for both contemporary and archaeological samples.

On Evaluating the Predictability of Sea Surface Temperature Using Entropy

Sea surface temperature (SST) has important impacts on the global ecology, and having a good understanding of the predictability, i.e., the possibility of achieving accurate prediction, of SST can help us monitor the marine environment and climate change, and guide the selection and design of SST prediction methods. However, existing studies for analyzing SST mostly measure the rising or falling trends of SST. To address this issue, we introduce a temporal-correlated entropy to quantify the predictability of SST series from both global coarse-grained and local fine-grained aspects, and make SST prediction with multiple deep learning models to prove the effectiveness of such predictability evaluation method. In addition, we explore the dynamics of SST predictability by dividing the time range of interest into consecutive time periods, evaluating the corresponding predictability of SST for each time period, and analyzing the stability of the predictability of SST over time. According to the experiments, the SST predictability values near the poles and equator are really high. The average SST predictability values of the East China Sea, Bohai Sea, and Antarctic Ocean are 0.719, 0.706, and 0.886, respectively, and the size relationship of the SST predictability in the three local sea areas is consistent with our prediction results using multiple representative SST prediction methods, which corroborates the reliability of the predictability evaluation method. In addition, we found that the SST predictability in the Antarctic Ocean changes more dramatically over time than in the East China Sea and the Bohai Sea. The results of SST predictability and its dynamic analysis indicate that global warming, ocean currents, and human activities all have significant impacts on the predictability of SST.

Illegal pollution loading accelerate the oxygen deficiency along the coastal lagoons of eastern Red Sea

The current study attempts to show how the two coastal lagoons near the eastern Red Sea lose oxygen when there is a significant input of organic waste. The strain caused by this problem is being increased by the expanding internal population migration trend toward the coastline region. The two main environmental factors that control when the marine environment changes from oxic to suboxic and eventually to anoxic conditions are the quantity of organic matter and the mixing of the water column. The samples were taken between the years of 2017 and 2018 in both the summer and the winter from the lagoons of Al-Shabab and Al-Arbaeen. Both places were situated on the Red Sea’s eastern shore. The quantity of DO along both lagoons was extremely important since it frequently indicates hypoxic to anoxic conditions. In the current study, the Al-Arbaeen lagoon’s peak anoxia was noted in both the summers of 2017 and 2018. In the Al-Arbaeen lagoon, the maximum concentration of H2S was recorded at 48.21 μM in 2017 and 45.67 μM in 2018, respectively. The current work unequivocally demonstrates how NO3 and NO2 are lost as ammonia builds up. As is obvious, the Al-Arbaeen lagoon recorded the highest level of TOC during the 2017 summer, with a concentration of 329 μM. The distribution of DO and TOC at both lagoons shows a clear correlation between the high level of TOC and oxygen consumption.

Pulsed turbidite and methane seep records in the north western South China Sea since the last glacial maximum

The small-scale event layers in the continental margin contain abundant dynamic environment information, and pose a challenge to the interpretation of continuous sedimentary records, giving geological significance to their accurate identify and possible genesis. Here, pulsed turbidite layers since the last glacial maximum (LGM) in a gravity core in the northwestern South China Sea (SCS) was analyzed to investigate the precisely identification, possible causes and the role of marine environmental change during the late Quaternary in formation of these small-scale event layers in the SCS. Eight potential pulsed turbidite layers, according to the petrographic characteristics, grain size parameters and element geochemistry, were identified. Meanwhile, indicators including total sulfur (TS)/total organic carbon (TOC) ratio, CaCO3 content, and chromium-reducible sulfur (CRS) revealed these horizons were mostly related to methane seep events. Constrained by foraminifera shells AMS14C results, these events were determined to have occurred from the LGM to early Holocene, Similar records in the northern and southern slopes suggests the universal occurrence of these small-scale layers in the SCS. The comprehensive analysis showed that the development of these event layers over the past 25 ka can be divided into three stages, 25-15.5 ka, 15.5-7 ka and 7 ka to present. Late Quaternary Ocean environment changes, especially sea level and bottom water temperature, controlled the occurrence of regional small-scale event layers in the SCS. The regional scale mechanism is that the pressure and temperature change affect the stability of hydrate and the methane seepage, and thus the strata stability. Corresponding to the lowest, the rapid increase and the highest levels of the sea level and bottom water temperature, the temporal evolution pattern of small-scale event layers in the SCS showed a highest, decreased and lowest frequency, respectively. The linkage between the late Quaternary marine environmental change and turbidite deposition through gas activities in this study can act as a useful reference for further understanding the continental margin sedimentary process.

Revealing the Paleo-ocean Environment of OSM-XX in the Western Pacific Magellan Seamount with Mineralogical and Geochemical Properties of Ferromanganese Crust

AbstractVariations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12′ 7.2″ E and 16° 8.16′ 9.6″ N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36–32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.망간각의 지화학적, 광물학적 특성의 변화는 인근 환경 변화를 반영한다. 따라서 서태평양 마젤란해산군 OSM-XX의 망간각에 대한 특성 파악과 고해양 복원 연구를 위하여 지화학적, 광물학적 분석을 각각 micro X-ray fluorescence (μ-XRF) 과 X-ray diffraction (XRD)를 이용하여 실시하였다. OSM-XX의 망간각은 인산염화 여부 및 구조에 의해 인산염화 작용을 받은 부분(L4-L5), 인산염화 작용을 받지 않은 치밀한 부분(L3), 인산염화 작용을 받지 않은 다공성 부분(L1-L2)의 세 부분으로 구분되었다. 철망간 산화광물 층에서는 모두 버나다이트 피크가 확인되었으며, 인산염화 작용을 받은 부분은 carbonate fluorapatite(CFA)의 존재와 높은 Ca, P의 특성을 나타내었다. 인산염화 작용을 받지 않은 치밀한 부분은 높은 Mn, Ni, Co를 나타내었고, 인산염화작용을 받지 않은 다공성 부분은 높은 Fe값과 detritus quartz, feldspar가 확인되었다. OSM-XX의 망간각이 성장하는동안 나타난 특성의 변화는 인근 해양환경의 변화를 반영하였다. 약 51.87 Ma의 연대를 나타내는 망간각의 인산염 퇴적체는 약 36-32 Ma의 전지구적 인산염화 작용에 의해 형성된 것으로 보이며, 이는 당시의 상승된 해수면 높이와 낮은 해수온을 지시한다. 또한, 치밀한 구조에서의 높은 Mn, Ni, Co, Mn/Fe 비는 강화된 산소최소층과 환원환경을 지시하며, 다공성 구조에서의 높은 Fe와 낮은 Mn/Fe 비는 약화된 산소최소층과 산화환경을 지시한다. 이는 마이오세-올리고세 경계의 Mi-1 빙하기가 끝난 후 환경변화를 반영하였다. 9 Ma부터 이어진 한랭화의 결과로 인한 저층류와 산소최소층의 강화에 의해 망간각 최외각의 Mn/Fe 비와 Co/Mn 비가 미세하게 증가하였지만, 6 Ma부터 태평양에 발생한 탄산염 용해율의 감소로 성장속도의 감소를 야기하였다.Keywords : ferromanganese crust, paleo-oceanography, redox condition, paleo productivity, western Pacific Magellan seamount