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2025, 47(8): 1-3.
Abstract:
2025, 47(8): 1-17.
doi: 10.12284/hyxb2025065
Abstract:
Observations indicate that the substantial freshwater transported to the southern part of the Makassar Strait by the South China Sea Throughflow (SCSTF) can influence the Indonesian Throughflow (ITF) via the “Freshwater Plug” effect. This article has conducted a series of numerical experiments and discovered that when the salinity in the Karimata Strait increased to that in the Makassar Strait, the volume and freshwater transport through the Karimata Strait are 3.52 Sv and 184.03 mSv, with an increase of 4.31% and a decrease of 27.27% compared with the control experiment, respectively. In the meantime, the volume transport in the upper 50m of the Makassar Strait is 0.11 Sv, with an increase of 34.69%. When the salinity in the Karimata Strait decreased by 0.1−0.6, the volume and freshwater transport through the Karimata Strait are 3.37 Sv and 294.44 mSv, with a decrease of 1.57% and an increase of 16.37% compared with the control experiment, respectively. Also, the volume transport in the upper 50m of the Makassar Strait is 0.07 Sv, with a decrease of 12.5%. These have proved the influence of freshwater transported by SCSTF on ITF. Comparing the salinity relaxation experiment with the topography closed experiment, the salinity relaxation experiment allows for significant changes in the freshwater transport through the Karimata Strait while only modestly affecting the volume transport. This enables an analysis of the impact of SCSTF’s surface water with low salinity on ITF. Meanwhile, we have compared the salinity relaxation experiment with the rainfall closed experiment, and the important impact of low salinity water transport in the South China Sea through the Karimata Strait to the Java Sea on the ITF in boreal winter is further verified.
Observations indicate that the substantial freshwater transported to the southern part of the Makassar Strait by the South China Sea Throughflow (SCSTF) can influence the Indonesian Throughflow (ITF) via the “Freshwater Plug” effect. This article has conducted a series of numerical experiments and discovered that when the salinity in the Karimata Strait increased to that in the Makassar Strait, the volume and freshwater transport through the Karimata Strait are 3.52 Sv and 184.03 mSv, with an increase of 4.31% and a decrease of 27.27% compared with the control experiment, respectively. In the meantime, the volume transport in the upper 50m of the Makassar Strait is 0.11 Sv, with an increase of 34.69%. When the salinity in the Karimata Strait decreased by 0.1−0.6, the volume and freshwater transport through the Karimata Strait are 3.37 Sv and 294.44 mSv, with a decrease of 1.57% and an increase of 16.37% compared with the control experiment, respectively. Also, the volume transport in the upper 50m of the Makassar Strait is 0.07 Sv, with a decrease of 12.5%. These have proved the influence of freshwater transported by SCSTF on ITF. Comparing the salinity relaxation experiment with the topography closed experiment, the salinity relaxation experiment allows for significant changes in the freshwater transport through the Karimata Strait while only modestly affecting the volume transport. This enables an analysis of the impact of SCSTF’s surface water with low salinity on ITF. Meanwhile, we have compared the salinity relaxation experiment with the rainfall closed experiment, and the important impact of low salinity water transport in the South China Sea through the Karimata Strait to the Java Sea on the ITF in boreal winter is further verified.
2025, 47(8): 18-25.
doi: 10.12284/hyxb2025063
Abstract:
Based on actual wave measurement data, combined with stochastic wave theory and the JONSWAP spectrum, the probability of freak waves in the northwestern part of the South China Sea was conducted. The characteristics of the number of freak waves and wave elements in the sea area were statistically analyzed by the buoy observation data, and the correlation characteristics between the effective wave height and the main parameters such as period and wind speed were explored. The results indicate that the occurrence probability of freak waves in the northwestern South China Sea is0.0059 %. Analyzing the distribution of the significant wave steepness δ in different seasons of this area, it was found that the frequency of swells in the waves is relatively high during the spring transition period and the southwest monsoon season, which may be one of the reasons for the relatively high probability of freak wave occurrences in these two seasons. Regarding the annual distribution characteristics, there is a high correlation between significant wave height and mean period, while freak waves show virtually no correlation. The correlation coefficient between annual significant wave height and wind speed is 0.83, and for freak waves, it is 0.63, indicating that the annual distribution of waves is greatly influenced by wind waves. The relative proportion of swells in the mixed zone of wind waves and swells may have a certain impact on the generation of freak waves.
Based on actual wave measurement data, combined with stochastic wave theory and the JONSWAP spectrum, the probability of freak waves in the northwestern part of the South China Sea was conducted. The characteristics of the number of freak waves and wave elements in the sea area were statistically analyzed by the buoy observation data, and the correlation characteristics between the effective wave height and the main parameters such as period and wind speed were explored. The results indicate that the occurrence probability of freak waves in the northwestern South China Sea is
2025, 47(8): 26-34.
doi: 10.12284/hyxb2025079
Abstract:
The Zhujiang River Estuary, a typical subtropical large-scale estuary, exhibits significant interactions between diurnal and semi-diurnal tides. Under the combined impacts of global climate change and intensive human activities, its tidal dynamics system has undergone notable variations. This study focuses on the nonlinear coupling mechanisms between diurnal tides (K1, O1) and semi-diurnal tides (M2, S2), developing an integrated evaluation framework that combines constituent amplitude ratios, relative phase analysis, and skewness method. This approach systematically reveals the spatiotemporal characteristics and driving mechanisms of barotropic tidal deformation in the Pearl River Estuary. The results include: (1) Tidal asymmetry transitions from ebb dominance at the estuary mouth to flood dominance at the upper estuary, with the controlling mechanism shifting from astronomical constituent interactions (O1/K1/M2) in the outer estuary to synergistic effects of semi-diurnal constituents (S2, M2) and shallow-water constituents (M4, MS4) in the upper reaches; (2) From 2010 to 2020, upstream constituents exhibited amplitude attenuation and phase increases, leading to a reversal from flood-to-ebb dominated asymmetry. Negative asymmetry induced by astronomical constituent interactions intensified, while the contribution of high-frequency constituents decreased; (3) In offshore areas, ebb-dominated asymmetry weakened, with emerging positive asymmetry driven by interactions between astronomical and shallow-water constituents; (4) The tidal dynamics system of the Pearl River Estuary has undergone significant long-term adaptive adjustments. Due to the combined influences of large-scale infrastructure construction, water resource allocation projects, and sea level rise, coastline and terrain both occur significant changes, which further has driven middle-to-long term adjustment of tidal dynamics. This study provides a novel analytical framework for understanding tidal system evolution under multi-scale perturbations and offers crucial insights for integrated estuarine management.
The Zhujiang River Estuary, a typical subtropical large-scale estuary, exhibits significant interactions between diurnal and semi-diurnal tides. Under the combined impacts of global climate change and intensive human activities, its tidal dynamics system has undergone notable variations. This study focuses on the nonlinear coupling mechanisms between diurnal tides (K1, O1) and semi-diurnal tides (M2, S2), developing an integrated evaluation framework that combines constituent amplitude ratios, relative phase analysis, and skewness method. This approach systematically reveals the spatiotemporal characteristics and driving mechanisms of barotropic tidal deformation in the Pearl River Estuary. The results include: (1) Tidal asymmetry transitions from ebb dominance at the estuary mouth to flood dominance at the upper estuary, with the controlling mechanism shifting from astronomical constituent interactions (O1/K1/M2) in the outer estuary to synergistic effects of semi-diurnal constituents (S2, M2) and shallow-water constituents (M4, MS4) in the upper reaches; (2) From 2010 to 2020, upstream constituents exhibited amplitude attenuation and phase increases, leading to a reversal from flood-to-ebb dominated asymmetry. Negative asymmetry induced by astronomical constituent interactions intensified, while the contribution of high-frequency constituents decreased; (3) In offshore areas, ebb-dominated asymmetry weakened, with emerging positive asymmetry driven by interactions between astronomical and shallow-water constituents; (4) The tidal dynamics system of the Pearl River Estuary has undergone significant long-term adaptive adjustments. Due to the combined influences of large-scale infrastructure construction, water resource allocation projects, and sea level rise, coastline and terrain both occur significant changes, which further has driven middle-to-long term adjustment of tidal dynamics. This study provides a novel analytical framework for understanding tidal system evolution under multi-scale perturbations and offers crucial insights for integrated estuarine management.
2025, 47(8): 35-47.
doi: 10.12284/hyxb2025069
Abstract:
Accurate parameterization of the momentum flux plays a decisive role in ocean and atmospheric hazards and climate change. However, the Wave Coherent (WC) stress, as one of the uncertainties factors, modulates the momentum flux severely. In this paper, using the observation from a fixed platform located in the Marine Meteorological Science Experiment Base at Bohe of China Meteorological Administration, the WC stress is extracted from the cospectrum of horizontal and vertical perturbations. The observation shows that the contribution of WC stress to total wind stress relies on the angle difference between wind and wave direction: it approaches zero when the angle difference is 90° and accounts for 20%−25% when the angle is ～180°. To describe the WC stress, the scheme of Janssen (1911, J91) and Zou et al. (2024, Z24) is compared. The result shows that J91 can underestimate the WC stress by about 1−2 orders of magnitude, while Z24 behaves better. The WC stress given by J91 decreases with height, giving a wind profile that follows Monin-Obukhov Similarity Theory (MOST); while WC stress given by Z24 firstly increases then decreases, with the height of its maximum being influenced by atmospheric stability, which leads to higher wind speeds near (or away from) the sea surface under stable (or unstable) conditions compared to the J91 scheme when swell exerted upward momentum flux. A new method to parameterize the momentum flux is also given by including the WC stress in this paper. The result shows that it has a high correlation coefficient in the wind speed range of 3–7 m/s and a smaller overall sample bias than the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.5.
Accurate parameterization of the momentum flux plays a decisive role in ocean and atmospheric hazards and climate change. However, the Wave Coherent (WC) stress, as one of the uncertainties factors, modulates the momentum flux severely. In this paper, using the observation from a fixed platform located in the Marine Meteorological Science Experiment Base at Bohe of China Meteorological Administration, the WC stress is extracted from the cospectrum of horizontal and vertical perturbations. The observation shows that the contribution of WC stress to total wind stress relies on the angle difference between wind and wave direction: it approaches zero when the angle difference is 90° and accounts for 20%−25% when the angle is ～180°. To describe the WC stress, the scheme of Janssen (1911, J91) and Zou et al. (2024, Z24) is compared. The result shows that J91 can underestimate the WC stress by about 1−2 orders of magnitude, while Z24 behaves better. The WC stress given by J91 decreases with height, giving a wind profile that follows Monin-Obukhov Similarity Theory (MOST); while WC stress given by Z24 firstly increases then decreases, with the height of its maximum being influenced by atmospheric stability, which leads to higher wind speeds near (or away from) the sea surface under stable (or unstable) conditions compared to the J91 scheme when swell exerted upward momentum flux. A new method to parameterize the momentum flux is also given by including the WC stress in this paper. The result shows that it has a high correlation coefficient in the wind speed range of 3–7 m/s and a smaller overall sample bias than the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.5.
2025, 47(8): 48-54.
doi: 10.12284/hyxb2025071
Abstract:
To investigate the impact of fluid viscosity on flux during double-diffusive convection, a gradient-concentration double-diffusion experiment was designed, where viscosity increases with concentration. Precisely formulated sugar-salt solutions based on mass fraction were injected into a test tank equipped with an intermediate baffle, controlling the salt-fingering density stability ratio at 1.073 and the diffusion-dominated density stability ratio at 0.93. After removing the baffle, a stationary sugar-salt two-layer system formed within the tank. To accurately evaluate double-diffusive phenomena and minimize experimental errors, three time intervals were established for the double-diffusion tests: 300 s, 600 s, and1800 s. The experimental results revealed that short-term flux is significantly reduced under the influence of viscosity. However, this effect becomes masked by subsequent diffusive fluxes as time progresses. Both salt-fingering and diffusion-dominated double-diffusion exhibit nonlinear relationships between sugar flux and viscosity. In diffusion-dominated double-diffusion, a power-law correlation was established between the flux ratio γ* and viscosity ratio. Nonetheless, the discrepancy between γ and the viscosity ratios of salt finger fluxes is relatively intricate and necessitates a more exhaustive analysis.
To investigate the impact of fluid viscosity on flux during double-diffusive convection, a gradient-concentration double-diffusion experiment was designed, where viscosity increases with concentration. Precisely formulated sugar-salt solutions based on mass fraction were injected into a test tank equipped with an intermediate baffle, controlling the salt-fingering density stability ratio at 1.073 and the diffusion-dominated density stability ratio at 0.93. After removing the baffle, a stationary sugar-salt two-layer system formed within the tank. To accurately evaluate double-diffusive phenomena and minimize experimental errors, three time intervals were established for the double-diffusion tests: 300 s, 600 s, and
2025, 47(8): 55-68.
doi: 10.12284/hyxb2025090
Abstract:
Mangrove ecosystem has a high carbon burial efficiency. In estuarine areas, influenced by multiple factors such as rivers and tides, the process of carbon preservation becomes more complex. This study focuses on sediment cores collected from mangrove and mutflat at the Maowei Sea estuary of Qinjiang River. Using the Diffusive Gradients in Thin Films (DGT) technique to obtain in situ concentration distributions of Fe(Ⅱ) and S(−Ⅱ) in the pore water, combined with organic carbon parameters (DOC, TOC and δ13C), we investigate the biogeochemical processes of iron, sulfur and the interaction relationships between carbon burial. The results indicate that the sediment carbon storage increased by 63.1% from the upper tide zone to the middle tide zone. There is an obvious redox stratification phenomenon in mangrove sediments, and transition between the oxidation zone and the reduction zone occurs at a depth of approximately 5 cm. TOC shows a significant positive correlation with Fe(Ⅱ) and S(−Ⅱ), which reflects that higher content of organic carbon burial promotes microbial iron reduction (MIR) and microbial sulfate reduction (MSR). Meanwhile, the generated S(−Ⅱ) chemically reduces and releases Fe(Ⅱ). However, in the middle tide zone with high TOC, Fe(Ⅱ), and S(−Ⅱ) concentrations, the local competition between MIR and MSR is particularly intense. Therefore, the middle tide zone is a critical area for studying carbon burial in mangrove ecosystem, and the redox changes driven by tides play a crucial regulatory role in the coupling of carbon, iron, and sulfur. The mechanisms of carbon burial and its interaction with iron and sulfur in mangrove sediments revealed in this study provide crucial insights for understanding the carbon sequestration function and biogenic element cycling in mangrove wetlands.
Mangrove ecosystem has a high carbon burial efficiency. In estuarine areas, influenced by multiple factors such as rivers and tides, the process of carbon preservation becomes more complex. This study focuses on sediment cores collected from mangrove and mutflat at the Maowei Sea estuary of Qinjiang River. Using the Diffusive Gradients in Thin Films (DGT) technique to obtain in situ concentration distributions of Fe(Ⅱ) and S(−Ⅱ) in the pore water, combined with organic carbon parameters (DOC, TOC and δ13C), we investigate the biogeochemical processes of iron, sulfur and the interaction relationships between carbon burial. The results indicate that the sediment carbon storage increased by 63.1% from the upper tide zone to the middle tide zone. There is an obvious redox stratification phenomenon in mangrove sediments, and transition between the oxidation zone and the reduction zone occurs at a depth of approximately 5 cm. TOC shows a significant positive correlation with Fe(Ⅱ) and S(−Ⅱ), which reflects that higher content of organic carbon burial promotes microbial iron reduction (MIR) and microbial sulfate reduction (MSR). Meanwhile, the generated S(−Ⅱ) chemically reduces and releases Fe(Ⅱ). However, in the middle tide zone with high TOC, Fe(Ⅱ), and S(−Ⅱ) concentrations, the local competition between MIR and MSR is particularly intense. Therefore, the middle tide zone is a critical area for studying carbon burial in mangrove ecosystem, and the redox changes driven by tides play a crucial regulatory role in the coupling of carbon, iron, and sulfur. The mechanisms of carbon burial and its interaction with iron and sulfur in mangrove sediments revealed in this study provide crucial insights for understanding the carbon sequestration function and biogenic element cycling in mangrove wetlands.
2025, 47(8): 69-81.
doi: 10.12284/hyxb2025077
Abstract:
To address the issue of insufficient generalization in underwater image enhancement algorithms caused by the scarcity of labeled underwater image data, we propose a semi-supervised underwater image enhancement framework based on the Mean-Teacher model. A multi-scale network integrating illumination and gradient priors, termed IGP-Net (Illumination and Gradient Prior Network), is designed as the backbone of the Mean-Teacher framework. IGP-Net consists of three key modules: (1) the Multi-Scale Lighting Perception module (MSLP), which extracts multi-scale features from degraded images and incorporates illumination and gradient priors to enhance image contrast; (2) the Multi-Channel detail Enhancement module (MCE), which performs channel-wise decomposition and color compensation on the initially enhanced images to correct color distortion; and (3) the Parallel Attention module (PC), which leverages both pixel and channel attention mechanisms to emphasize the correlation between illumination and color information, achieving better color balance. Quantitative comparisons and qualitative analyses on public datasets demonstrate that the proposed method outperforms several state-of-the-art algorithms across multiple key metrics. Furthermore, experiments on underwater object detection tasks show that the enhanced images generated by our method significantly improve detection performance.
To address the issue of insufficient generalization in underwater image enhancement algorithms caused by the scarcity of labeled underwater image data, we propose a semi-supervised underwater image enhancement framework based on the Mean-Teacher model. A multi-scale network integrating illumination and gradient priors, termed IGP-Net (Illumination and Gradient Prior Network), is designed as the backbone of the Mean-Teacher framework. IGP-Net consists of three key modules: (1) the Multi-Scale Lighting Perception module (MSLP), which extracts multi-scale features from degraded images and incorporates illumination and gradient priors to enhance image contrast; (2) the Multi-Channel detail Enhancement module (MCE), which performs channel-wise decomposition and color compensation on the initially enhanced images to correct color distortion; and (3) the Parallel Attention module (PC), which leverages both pixel and channel attention mechanisms to emphasize the correlation between illumination and color information, achieving better color balance. Quantitative comparisons and qualitative analyses on public datasets demonstrate that the proposed method outperforms several state-of-the-art algorithms across multiple key metrics. Furthermore, experiments on underwater object detection tasks show that the enhanced images generated by our method significantly improve detection performance.
2025, 47(8): 82-91.
doi: 10.12284/hyxb2025073
Abstract:
To enable underwater robots to quickly adapt to various application scenarios, a modular and reconfigurable Unmanned Underwater Vehicle (UUV) was designed. The UUV employs rectangular modules as its basic components, achieving non-electrical-contact interconnection through wireless power and data transmission, thereby eliminating the need for traditional watertight connectors. The modules are categorized into control and extension types, allowing flexible combinations based on task requirements. A specialized slider-and-clasp structure facilitates rapid assembly and secure connections between modules. Module interconnection and expansion capabilities were validated through modular assembly tests, and underwater experiments confirmed the feasibility of inter-module communication and wireless power transmission. Wireless power transfer tests demonstrated stable voltage output in underwater environments, meeting operational requirements. Prototype underwater operation tests further validated the feasibility of the overall design. This modular and reconfigurable design offers extensive possibilities for flexible deployment and functional expansion of UUVs in various application scenarios.
To enable underwater robots to quickly adapt to various application scenarios, a modular and reconfigurable Unmanned Underwater Vehicle (UUV) was designed. The UUV employs rectangular modules as its basic components, achieving non-electrical-contact interconnection through wireless power and data transmission, thereby eliminating the need for traditional watertight connectors. The modules are categorized into control and extension types, allowing flexible combinations based on task requirements. A specialized slider-and-clasp structure facilitates rapid assembly and secure connections between modules. Module interconnection and expansion capabilities were validated through modular assembly tests, and underwater experiments confirmed the feasibility of inter-module communication and wireless power transmission. Wireless power transfer tests demonstrated stable voltage output in underwater environments, meeting operational requirements. Prototype underwater operation tests further validated the feasibility of the overall design. This modular and reconfigurable design offers extensive possibilities for flexible deployment and functional expansion of UUVs in various application scenarios.
2025, 47(8): 92-100.
doi: 10.12284/hyxb2025067
Abstract:
Sea surface gusts play a critical role in the utilization of ocean resources, marine research, and the safety of maritime transportation and offshore construction. However, current observation methods are limited, resulting in significant data gaps in surface gust measurements. Lin Jing et al. corrected sea surface wind speeds based on the difference in backscattering coefficients between the C and Ku bands observed by the HY-2B radar altimeter, thereby deriving gust wind speeds at nadir points, although the spatial coverage remained relatively limited. Building upon this approach, the present study employs the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) mission, whose observational principles are similar to those of radar altimeters. By utilizing the difference in Ku-band and Ka-band backscattering coefficients and using ERA5 sea surface wind speed as a reference, surface wind speeds are corrected to retrieve gust speeds, aiming to expand observation coverage and improve observational efficiency. Validation against ERA5 gust data yields a correlation coefficient (R) of 0.96, a root mean square error (RMSE) of 1.79 m/s, a mean bias (Bias) of 0.73 m/s, and a standard deviation (Std) of 1.64 m/s. Comparison with simultaneous NDBC buoy observations shows an R of 0.91, an RMSE of 1.50 m/s, a Bias of −0.15 m/s, and a Std of 1.50 m/s, indicating that gust wind speeds retrieved from DPR data demonstrate good reliability. Furthermore, by replacing ERA5 sea surface wind speeds with NDBC buoy measurements, the R increases to 0.95, the RMSE decreases to 1.10 m/s, the Bias is −0.07 m/s, and the Std remains at 1.50 m/s, further improving the retrieval results. These findings highlight that accurate sea surface wind speeds have a significant positive impact on the accuracy of gust wind retrievals.
Sea surface gusts play a critical role in the utilization of ocean resources, marine research, and the safety of maritime transportation and offshore construction. However, current observation methods are limited, resulting in significant data gaps in surface gust measurements. Lin Jing et al. corrected sea surface wind speeds based on the difference in backscattering coefficients between the C and Ku bands observed by the HY-2B radar altimeter, thereby deriving gust wind speeds at nadir points, although the spatial coverage remained relatively limited. Building upon this approach, the present study employs the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) mission, whose observational principles are similar to those of radar altimeters. By utilizing the difference in Ku-band and Ka-band backscattering coefficients and using ERA5 sea surface wind speed as a reference, surface wind speeds are corrected to retrieve gust speeds, aiming to expand observation coverage and improve observational efficiency. Validation against ERA5 gust data yields a correlation coefficient (R) of 0.96, a root mean square error (RMSE) of 1.79 m/s, a mean bias (Bias) of 0.73 m/s, and a standard deviation (Std) of 1.64 m/s. Comparison with simultaneous NDBC buoy observations shows an R of 0.91, an RMSE of 1.50 m/s, a Bias of −0.15 m/s, and a Std of 1.50 m/s, indicating that gust wind speeds retrieved from DPR data demonstrate good reliability. Furthermore, by replacing ERA5 sea surface wind speeds with NDBC buoy measurements, the R increases to 0.95, the RMSE decreases to 1.10 m/s, the Bias is −0.07 m/s, and the Std remains at 1.50 m/s, further improving the retrieval results. These findings highlight that accurate sea surface wind speeds have a significant positive impact on the accuracy of gust wind retrievals.
2025, 47(8): 101-115.
doi: 10.12284/hyxb2025081
Abstract:
The fusion of multi-source data, such as satellite gravity inversion and shipboard sonar bathymetry, is the core technology for constructing large-scale high-precision deep-sea topographic models. However, existing methods are usually difficult to consider the local topographic details and global trends, so this paper proposes a method for constructing a high-precision seafloor topographic model of the deep sea based on the weighted fusion of multi-source data in the frequency domain. First, data format conversion, data cleaning and datum unification are performed on the multi-source data; then, the six global terrain models corresponding to the survey area are processed by frequency division and weighted fusion, and the fusion weights are iteratively optimized to obtain the initial fusion results with the constraints of the bathymetric deviation of the local ship’s measured terrain and the fused model; finally, the local terrain details are constructed by combining the local ship’s measured terrain and the initial fusion results, so as to realize the construction of a high-accuracy seabed topographic model over a wide range of survey areas. A case study in the southern part of Greenland Island was presented, and the results showed that the root-mean-square error (RMSE) of the seafloor topography model constructed by the proposed method significantly decreased, with RMSE 17.15%, 16.50%, 16.63%, 16.67%, and 9.99% lower than that of the nearest-neighbor interpolation, inverse-distance-weighted, natural-neighbor interpolation, kriging interpolation methods, and the remove-and-recovery method, respectively. The improvement in the coefficient of determination R2 with the IBCAO5.0 model was about 8.82%, 8.27%, 8.27%, 8.41% and 16.09%, respectively, and the information of the overall trend of the terrain and the local details are effectively guaranteed.
The fusion of multi-source data, such as satellite gravity inversion and shipboard sonar bathymetry, is the core technology for constructing large-scale high-precision deep-sea topographic models. However, existing methods are usually difficult to consider the local topographic details and global trends, so this paper proposes a method for constructing a high-precision seafloor topographic model of the deep sea based on the weighted fusion of multi-source data in the frequency domain. First, data format conversion, data cleaning and datum unification are performed on the multi-source data; then, the six global terrain models corresponding to the survey area are processed by frequency division and weighted fusion, and the fusion weights are iteratively optimized to obtain the initial fusion results with the constraints of the bathymetric deviation of the local ship’s measured terrain and the fused model; finally, the local terrain details are constructed by combining the local ship’s measured terrain and the initial fusion results, so as to realize the construction of a high-accuracy seabed topographic model over a wide range of survey areas. A case study in the southern part of Greenland Island was presented, and the results showed that the root-mean-square error (RMSE) of the seafloor topography model constructed by the proposed method significantly decreased, with RMSE 17.15%, 16.50%, 16.63%, 16.67%, and 9.99% lower than that of the nearest-neighbor interpolation, inverse-distance-weighted, natural-neighbor interpolation, kriging interpolation methods, and the remove-and-recovery method, respectively. The improvement in the coefficient of determination R2 with the IBCAO5.0 model was about 8.82%, 8.27%, 8.27%, 8.41% and 16.09%, respectively, and the information of the overall trend of the terrain and the local details are effectively guaranteed.
2025, 47(8): 116-128.
doi: 10.12284/hyxb2025075
Abstract:
As a core component of benthic habitat mapping, the detection and classification of deep-sea sediment provides basic information for deep-sea resource exploration and ecological protection. However, due to the limitation of the resolution of deep-sea acoustic observation, the traditional method of sediment classification based on multibeam bathymetry and backscatter intensity information suffers from the difficulty of interpretation and low confidence caused by the mixed sediment on the seafloor. For this reason, this paper innovatively applies multibeam water column data to deep-sea bottom classification, and proposes a mixed bottom classification method based on the multidimensional waveform characteristics of the bottom echo sequence. Firstly, the multidimensional bottom echo waveform features are extracted with the help of the sequence echo information of the interaction between the water body and the seafloor; secondly, a decision fusion classification model under the constraints of water column bottom echo abundance interpretation is constructed by taking into account the mixing of sediments within the intrinsic observational resolution; lastly, the experiments are carried out by using the Arctic shipborne multibeam data for the classification and abundance estimation of the three kinds of sediments, including the sheet basalt, the basalt breccia, and the volcanic glass, the overall accuracy and Kappa coefficient reached 92.46% and 0.89, which are increased by 11.05% and 0.21 respectively compared with the traditional sonar image classification method, providing a new strategy for spatial prediction mapping of deep seabed benthic environment.
As a core component of benthic habitat mapping, the detection and classification of deep-sea sediment provides basic information for deep-sea resource exploration and ecological protection. However, due to the limitation of the resolution of deep-sea acoustic observation, the traditional method of sediment classification based on multibeam bathymetry and backscatter intensity information suffers from the difficulty of interpretation and low confidence caused by the mixed sediment on the seafloor. For this reason, this paper innovatively applies multibeam water column data to deep-sea bottom classification, and proposes a mixed bottom classification method based on the multidimensional waveform characteristics of the bottom echo sequence. Firstly, the multidimensional bottom echo waveform features are extracted with the help of the sequence echo information of the interaction between the water body and the seafloor; secondly, a decision fusion classification model under the constraints of water column bottom echo abundance interpretation is constructed by taking into account the mixing of sediments within the intrinsic observational resolution; lastly, the experiments are carried out by using the Arctic shipborne multibeam data for the classification and abundance estimation of the three kinds of sediments, including the sheet basalt, the basalt breccia, and the volcanic glass, the overall accuracy and Kappa coefficient reached 92.46% and 0.89, which are increased by 11.05% and 0.21 respectively compared with the traditional sonar image classification method, providing a new strategy for spatial prediction mapping of deep seabed benthic environment.
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