In this paper, the mesoscale model WRF-ARW (Weather Research and Forecasting Model-Advanced Research WRF)(Version 4.0) is used to simulate a typical sea breeze front case in Hainan Island under different weather conditions with high numerical resolution. By designing sensitivity tests for local urbanization, the influence of coastal urbanization on sea breeze fronts in Hainan Island and its possible influencing mechanism are analyzed. The results show that the sea breeze front structure difference caused by urbanization is the result of thermal and dynamic effects. The friction effect of the underlying surface and the enhancement of urban heat island hinder the sea breeze from advancing inland, weaken the cooling and humidification effect of the sea breeze front, and result in a relative lagging of the sea breeze front. The high sea-land thermal difference caused by urbanization enhances the sea breeze wind speed and amplitude, and the vertical updraft and sea breeze circulation thickness in front of the sea breeze front are significantly enhanced. The influence of urbanization on the advance of sea breeze fronts varies during different stages of development. In the early stages of the development of sea breeze fronts, the driving effect of the thermal difference between land and sea is offset by the hindering effect of friction, resulting in no significant impact on the advance of sea breeze fronts. In the strong stage of development of sea breeze fronts, the thermal difference between inland cities and non-urban areas under urbanization conditions has increased, hindering the advance of sea breeze fronts towards inland areas, resulting in a decrease in the penetration distance of sea breeze fronts inland. The influence of urbanization on the advance of sea breeze fronts varies under different weather conditions. Compared to clear weather, the thermal difference between urban and non-urban areas under cloudy weather is slightly stronger, strengthening the hindering effect of urban heat island effect on the advance of sea breeze fronts towards inland areas, resulting in a slightly longer lag distance of sea breeze fronts. Furthermore, when land use transitions to towns occur, net radiation energy exchange with atmospheric air decreases leading to notable declines in latent heat flux alongside increases in sensible heat flux levels. This increased the underlying surface temperature, enhanced the vertical upward movement of sea breeze, and thus caused the increase in boundary layer height.

There are strong exchange of matter and energy and complex dynamic processes between mesoscale eddies and submesoscale fronts at their edges. At present, the investigation of mesoscale eddies has become more and more mature, but because of the small spatial scale and rapid time change of the submesoscale front, it is a great challenge to investigate its three-dimensional structure. In this paper, a new method is proposed to investigate the submesoscale front at the edge of the ocean mesoscale eddy. Firstly, the submesoscale front at the edge of the mesoscale eddies is identified using multi-source satellite remote sensing data, and then the multi-type shipborne survey equipment is used for multidisciplinary investigation. A submesoscale front at the edge of typical eddies in the Kuroshio Extension area from August 21 to August 25, 2023 is investigated by using this method. The survey method proposed in this paper can effectively identify, track and investigate the submesoscale front at the edge of mesoscale eddies.

The Chukchi Borderland served as the critical gateway for the inflow of Atlantic Water (AW, which is the most important heat storage layer in the Arctic Ocean) into the Canada Basin in the western Arctic Ocean. One of the key issues is how the AW and Pacific Winter Water (PWW) interacts in this complex topography region. The answer to this question will shed light on the important role of AW in the Arctic Ocean. In this study, based on the multi-sources’ quality controlled hydrographic data during 1999−2021, the variation of AW, PWW and the double-diffusive staircases in the Chukchi Borderland are studied in details. We identified three anomalous warm events of AW that occurred in year 2000, 2012 and 2018 with the maximum potential temperature over 1℃. The vertical averaged heat content between the PWW and AW shows a warming trend in the central and eastern region of the Chukchi Borderland. The major reason for this is the warming of PWW. The depth of PWW is more sensitive to the shifting of the Beaufort Gyre (BG) than that of the AW. The combined changes of PWW and AW lead to the variation of double-diffusive staircases, which show a regime shift from large to small thickness and to largely decayed in the Canada Basin. Our results suggest that the major mechanism for this transition is the cooling of AW along with the stronger stratification that restricts the vertical mixing for all.

Utilizing the molecular biomarkers of organic matter in marine sediments from the Antarctic Peninsula (D1-7) and adjacent waters of the South Orkney Islands (D5-6), the ecological relationships implicit in the reconstructed variations of planktonic productivity and population structure are examined in relation to the Biological Pump (BP)/Microbial Carbon Pump (MCP), as well as the efficiency of marine carbon sinks and storage. Over the past century, a series of molecular biomarkers in sediment cores has exhibited significant changes, reflecting substantial spatiotemporal evolution in upper ocean planktonic productivity/community structure and sedimentary carbon reservoirs. These changes are indeed linked to global climate variability. The research findings are as follows: (1) Based on the characteristics of molecular composition and chromatographic peak patterns of biomarker compounds, as well as parameters such as Main Peak Carbon (MH), Light Hydrocarbons/Heavy Hydrocarbons (L/H), Bacterial-Algal Ratio (nC₁₅ + nC₁₇ + nC₁₉), Large Phytoplankton Ratio (nC₂₁ + nC₂₃ + nC₂₅), and carbon preference index (CPI), it is evident that the primary source of sedimentary carbon is marine-derived organic carbon. Marine organisms serve as natural carbon sinks for carbon fixation and storage. (2) The sediments from the D5-6 region exhibit high organic matter enrichment, primarily influenced by factors such as higher surface water productivity, higher sedimentation rates (average of 0.19 cm/a), shallower water depths (385 m), and a reducing sedimentary environment (average Pr/Ph value of 0.95). These conditions favor the transport of Particulate Organic Carbon (POC) from the ocean surface to the deep sea via the Biological Pump (BP) process, facilitating rapid burial and storage. In contrast, sediments from the D1-7 region, characterized by greater water depths (1 100 m) and lower sedimentation rates (0.07 cm/a, experience degradation of carbonaceous compounds during sedimentation processes and subsequent oxidative degradation in an oxic environment (average Pr/Ph value of 1.22). Both processes are unfavorable for carbon sequestration in sediments. However, the control factor determining carbon preservation in sediments may predominantly be sedimentation rate. (3) Over the past century, the total abundance of zooplankton, primary productivity of phytoplankton, and biomass of diatoms and dinoflagellates in the waters near the Antarctic Peninsula and the South Orkney Islands have shown an increasing trend, while the biomass and proportion of coccolithophores have decreased (particularly evident near the Antarctic Peninsula). This indicates a declining trend in the effectiveness of the calcium carbonate pump while the silica pump dominated by diatoms is strengthening. The relative strengths of these two processes largely determine the structure and efficiency of the biological pump, as well as the proportion of organic and inorganic carbon transported to marine sediments. (4) The trends in molecular biomarker variations in the two sediment cores show certain comparability overall, with distinct stages. Following interdecadal shifts (since 1972), the waters near the South Orkney Islands experienced a significant increase in zooplankton abundance from a depth of 5-6 cm beginning in 1982. Particularly, during the periods of 1997 and 2012, zooplankton abundance witnessed a dramatic increase, indicating rapid changes in planktonic community structure under the backdrop of global warming. Variations in both decreased primary productivity of phytoplankton and increased zooplankton abundance contribute to significant uncertainties in the changes in the strength of the biological pump (enhancement/weakening). (5) In contrast, over the past century, the productivity of phytoplankton/diatoms and dinoflagellates in the waters near the Antarctic Peninsula has gradually increased, while microbial productivity/ancient archaeal biomass has decreased. This suggests a weakening of microbial carbon sequestration intensity, indicating a decrease in the efficiency of the microbial carbon pump (MCP). This underscores the crucial role of global warming in the fluctuations of phytoplankton productivity/biomass in marine waters. The biomass and composition characteristics of planktonic communities directly affect the transport of organic carbon in the upper water column and the efficiency of carbon sequestration in the MCP. As the largest carbon sink in the global ocean, the carbon sequestration capacity of the Antarctic may be diminishing.

The “fairy circle” represents a unique form of spatial self-organization found within coastal salt marsh ecosystems, profoundly influencing the productivity, stability, and resilience of these wetlands. Unmanned Aerial Vehicle (UAV) imagery plays a pivotal role in precisely pinpointing the “fairy circle” locations and deciphering their temporal and spatial development trends. However, identifying “fairy circle” pixels within two-dimensional images poses a considerable technical challenge due to the subtle differences in color and shape characteristics between these pixels and their surroundings. Therefore, intelligently and accurately identify “fairy circle” pixels from two-dimensional images and form individual “fairy circle” for the identified pixels were the current technical difficulties. This paper introduced an innovative approach to extract “fairy circle” from UAV images by integrating the SAM (Segment Anything Model) visual segmentation model with random forest machine learning. This novel method accomplished the recognition and extraction of individual “fairy circle” through a two-step process: segmentation followed by classification. Initially, we established Dice (Sørensen-Dice coefficient) and IOU (Intersection Over Union) evaluation metrics, and optimize SAM’s pre-trained model parameters, which produced segmentation mask devoid of attribute information by fully automated image segmentation. Subsequently, we aligned the segmentation mask with the original image, and utilized RGB (red, green, and blue) color channels and spatial coordinates to construct a feature index for the segmentation mask. These features underwent analysis and selection based on Out-of-Bag (OOB) error reduction and feature distribution patterns. Ultimately, the refined features were employed to train a random forest model, enabling the automatic identification and classification of “fairy circle” vegetation, common vegetation, and bare flat areas. The experimental results show that the average correct extraction rate of “fairy circle” is 96.1%, and the average wrong extraction rate is 9.5%, which provides methodological and technological support for the accurate depiction of the spatial and temporal pattern of “fairy circle” as well as the processing of coastal remote sensing images by UAVs.

Oil and plastic pollutants are a serious threat to marine ecosystems and have even been found in the Ross Sea of the Southern Ocean. In order to obtain low-temperature alkane degrading bacteria and plastic-degrading bacteria in the region, a total of twelve sediment samples were collected in the Ross Sea area for enrichment and isolation of alkane-degrading bacteria at low-temperature, and the diversity analyses of the tetradecane-enriched communities showed that the most dominant genera were Pseudomonas, Alcanivorax, Marinomonas, Pseudoalteromonas. The polyethylene terephthalate(PET)and polyethylene(PE)was further validated using the dominant alkane-degrading bacteria. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (ATR-FTIR) demonstrated that the four pure cultures of Pseudomonas pelagia R1-05-CR3, Pseudomonas taeanensis A11-04-CA4, Halomonas titanicae A11-02-7C2 and Rhodococcus cerastii R1-05-7C3 could degrade PE effectively. The results of UPLC-MS and SEM confirmed the PET degradation by isolates of R. cerastii R1-05-7C3, Microbacterium maritypicum RA1-00-CA1, and H. titanicae A11-02-7C2. In conclusion, this study reports the diversity of the tetradecane-enriched consortia at low-temperature and plastic degrading bacteria in the offshore sediments of the Ross Sea in the Southern Ocean, which play a selfpurifying role in in-situ environmental contamination, and also provided strain resources for the biodegradation of hydrocarbon and plastic contaminants at low temperature.

Coastal wetlands have important economic and ecological value. Rapid and accurate monitoring of the status of coastal wetlands is of great significance for the protection and management of coastal wetland resources. Due to factors such as the variability of the tide-level changes, similarity of vegetation spectra, and frequent cloud cover, remote sensing monitoring of coastal wetlands faced certain challenges. In this paper, we proposed a multi-technology coupled remote sensing classification method of coastal wetlands that considers tide-level changes and vegetation phenological characteristics. Based on the Google Earth Engine (GEE) platform, the Fmask (Function of mask) algorithm was first performed for cloud testing and cloud removal processing. Then, the S-G (Savitzky-Golay) filtering algorithm was used to reconstruct NDVI time series data and extract vegetation phenological characteristic parameters. In this phase, the random forest algorithm was applied for the classification of four vegetation types namely Phragmites australi, Suaeda salsa, Spartina alterniflora, and Imperata cylindrical. Finally, the Maximum Spectral Index Composite (MSIC) algorithm was used to generate composite images of the highest and lowest tide levels. The tidal flats and seawater were precisely extracted using the Otsu algorithm based on these two composite images. Combining these feature types, the refined remote sensing classification of coastal wetlands was ideally obtained. The results showed that start-of-season time, end-of-season time, length of season, base value, amplitude, and small seasonal integral were the six key vegetation phenological characteristic parameters for distinguishing different types of coastal wetland vegetation. Applying this method to classify coastal wetlands on the Yancheng coast, the overall classification accuracy was 96.50%, and the Kappa coefficient reached 0.957 1. Among the wetland vegetation, the highest user accuracy was 96.59% for Spartina alterniflora, followed by P. australi and Suaeda salsa, and the lowest was 93.55% for Imperata cylindrical. Compared with object-oriented methods, our method can extract the complete range of tidal flats, and the overall accuracy is improved by 10.25%, reflecting the potential application of vegetation phenological characteristics in remote sensing monitoring of dynamic changes in coastal wetlands.

In this paper, a high spatial-temporal resolution sea ice concentration estimation method for the Arctic melting season is proposed, aiming to improve the overestimation of sea ice concentration in seawater by the Global Navigation Satellite System-Reflectometry (GNSS-R). The method utilizes machine learning algorithms to extract feature parameters from the Delay Doppler Maps (DDM) obtained through GNSS-R and combines them with sea surface temperature data to establish a LightGBM model. The inversion results are then subjected to correlation analysis and evaluation against reference sea ice concentration values. The model’s performance is compared with the sea ice concentration product from OSI SAF, demonstrating good consistency, with correlation coefficient, mean absolute error, and root mean square error being 0.965, 0.061, and 0.090, respectively. This approach enables high-precision estimation of sea ice concentration in the Arctic marginal ice zone.

Sea surface temperature (SST) is one of the most important physical variables of the ocean, which provides the basic information of the climate system. Accurately SST forecasting system has a comprehensive and essential application. In recent years, AI-based SST forecasting methods have become popular and shown great potential. Based on the convolutional long and short-term memory neural network (ConvLSTM), this paper studies the influence of multi-scale input fields on SST prediction in the northern South China Sea. Multi-dimensional ensemble empirical mode decomposition method (MEEMD) is used to decompose the average daily SST into the spatial eigenmodes of differentiated scales. Input different combinations of eigenmodes into ConvLSTM for training and prediction experiments. Results show that when using all four SST eigenmodes, the RMSE of the predicted SST in 1−7 days is 0.4−0.8℃, decrease 0.2−1.2℃ compared with the original SST alone; the MAPE is 1%−6%, decrease 0.5%−10%; the spatial correlation coefficient is 99.5%−96.5%, improve 0.5%−3.5%. Moreover, the randomized experiments also further proved the method has a high universality. The prediction model based on deep learning needs to select the appropriate training data in order to further improve its prediction accuracy. This paper preliminarily explores the integration of artificial intelligence methods and physical concepts in SST prediction, which can provide some reference for future research.

Mangroves are a crucial ecological barrier for coastal zones, and sensitive areas to climate change and human activities, where benthic fauna responds directly to the sedimentary environment because of their intimate contact and relatively fixed settlement habitats. In-situ observations and sample collections were carried out at 7 stations in the mangrove area off the Chaoshan coastal zone, in April 2021, for further analysis of the sedimentary environment, meiofaunal communities, and eco-environment quality evaluation. A total of 15 meiofauna groups were identified. Free-living marine nematodes were the most dominant group, accounting for 90.32% of the total abundance of meiofauna; while polychaetes were the first in biomass (58.44%). The average abundance of meiofauna was slightly higher than that of the other mangrove forests. The spatial pattern of the meiofaunal abundance exhibited a similar distribution trend to that of the abundance of nematodes and the content of chlorophyll a (Chl a), phaeophorbide, organic carbon, and heavy metals (Cd, Zn, Cu, Cr, and Hg): all the parameters showed the highest values in the northern of the Lianyang River, and decreased towards the south and north. Meiofaunal communities in different patches shared a high similarity of 70%, and the best explanation factor for the differences in the meiofauna community was the content of heavy metal Pb. The abundance ratio of marine nematodes to copepods (N/C), the possible ecological risk index, and the sediment quality grading all indicated a poor environmental state in the area investigated.