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Rapid detection to long ship wake in synthetic aperture radar satellite imagery

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Journal of Oceanology and Limnology 2019年第5期37卷 1523-1532页

作者： CHEN Peng LI Xiunan ZHENG Gang second institute of oceanography Ministry of Natural Resources

The maritime administrative department employs synthetic aperture radar (SAR) satellite remote sensing technology to obtain evidence of illegal discharge of ships. If the ship is discharged during navigation, it forms a long dark wake on the SAR image due to the suppression of the Bragg wave by the oil fi lm. This study investigates key techniques for rapid detection of long ship wakes, thereby providing law enforcement agencies with candidate ships for possible discharge. This paper presents a rapid long ship wake detection method that uses satellite imaging parameters and the axial direction of the ship in images to determine the potential detection area of the wake. Then, the threshold of long ship wake detection is determined using statistical analysis, the area is binarized, and isolated points are removed using a morphological filter operator. The method was tested with ENVISAT Synthetic Aperture Radar and GF-3 SAR data, and results showed that the method was eff ective, and the overall accuracy of the decision reaches 71%. We present two innovations;one is a method that draws a Doppler shift curve, and uses the SAR imaging parameters to determine the detection area of the long wake to achieve rapid detection and reduce the image detection area. The other is where a classical linear fitting method is used to quickly and accurately determine whether the detected dark area is a long ship wake and realizes the twisted long ship wake detection caused by the sea surface flow field, which is otherwise diffi cult to detect by the traditional Radon and Hough transform methods. This method has good suppression performance for the dark spot false alarm formed by low speed wind region or upward flow. The method is developed for maritime ship monitoring system and will promote the operational application of maritime ship monitoring system.

关键词： marine pollution illegal discharge linear fi t oil spill synthetic aperture radar (SAR) long ship wake

Comparison of hydrodynamic influence between different types of bay reclamations

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Journal of Hydrodynamics 2018年第4期30卷 694-700页

作者：许雪峰何齐齐宋丹杨忠良俞亮亮 Key Laboratory of Engineering oceanography Second Institute of OceanographyState Oceanic Administration institute of Physical oceanography Ocean College Zhejiang University State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

Different reclamation types to be used for the tidal flat have different hydrodynamic influences on the bay. Numerical experiments based on the land reclamation（LR） and the mariculture reclamation（MR）, respectively, are conducted for the same reclamation project in the Shuangpantu, for quantitative comparisons. Results show that the MR has less influence on the hydrodynamic environment than the LR. The difference is more than 50%.

关键词： Hydrodynamic influence land reclamation （LR） mariculture reclamation （MR） numerical modeling tidal fiat

Effects of sea ice melt water input on phytoplankton biomass and community structure in the eastern Amundsen Sea

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Advances in Polar Science 2022年第1期33卷 14-27页

作者： FENG Yubin LI Dong ZHAO Jun PAN Jianming ZHANG Haisheng HAN Zhengbing ZHU Qiuhong second institute of oceanography Ministry of Natural Resources(MNR)Hangzhou 310000China

Sea ice melt water and circumpolar deep water(CDW)intrusion have important impacts on the ecosystem of the Amundsen Sea.In this study,samples of nutrients and phytoplankton pigments from nine stations in the eastern Amundsen Sea were collected during the austral summer.Based on in-situ hydrological observations,sea ice density data from satellite remote sensing,and chemical taxonomy calculations,the relationships between environmental factors and phytoplankton biomass and community structure were studied.The results showed that with increasing latitude,the contribution of sea ice melt water(MW%)and the stability of the water body increased,and the depth of the mixed layer(MLD)decreased.The integrated concentration of chlorophyll a(Chl-a)ranged from 21.4 mg·m^(−2) to 148.4 mg·m^(−2)(the average value was 35.7±53.4 mg·m^(−2)).Diatoms(diatoms-A[Fragilariopsis spp.,Chaetoceros spp.,and Proboscia spp.]and diatoms-B[Pseudonitzschia spp.])and Phaeocystis antarctica were the two most widely distributed phytoplankton groups and contributed 32%±16%and 28%±11%,respectively,of the total biomass.The contributions of Dinoflagellates,Chlorophytes,Cryptophytes,the high-iron group of P.antarctica,and Diatom group A were approximately 17%±8%,15%±13%,9%±6%,5%±9%,and 3%±7%,respectively.The area with the highest phytoplankton biomass was located near the ice-edge region,with a short time lag(T_(lag))between sampling and complete sea ice melt and a high MW%,while the area with the second-highest Chl-a concentration was located in the area affected by the upwelling of CDW,with thorough water mixing.Vertically,in the area with a short T_(lag) and a shallow MLD,the phytoplankton biomass and proportion of diatoms decreased rapidly with increasing water depth.In contrast,in the region with a long T_(lag) and limited CDW upwelling,the phytoplankton community was dominated by a relatively constant and high proportion of micro phytoplankton,and the phytoplankton biomass was low and relatively stable vertically.Generally,the phytoplankton comm

关键词： Amundsen Sea sea ice melt water mixed layer depth phytoplankton pigments biomass

Geochemical speciation and spatial distributions of phosphorus in surface sediments from the basin of the Marcus-Wake seamounts in the western Pacific Ocean

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Acta Oceanologica Sinica 2022年第4期41卷 80-90页

作者： Chao Yuan Fansheng Meng Xuying Yao Jianyu Ni Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China

The concentrations of five forms of phosphorus(P)including exchangeable or loosely adsorbed P(Ex-P),Febound P(Fe-P),authigenic P(Auth-P),detrital P(Det-P),and organic P(Org-P)from the basin among the Marcus-Wake seamounts(19.4°–24°N,156.5°–161.5°E)in the western Pacific Ocean were quantified using a sequential extraction method(SEDEX)to investigate the distribution and sources of different P species.Concentrations of total P(TP)varied from 14.0μmol/g to 44.1μmol/g,with an average of(32.4±7.7)μmol/g.Inorganic phosphorus,which was the major chemical form of sedimentary P,ranged from 12.6μmol/g to 40.6μmol/g,while the concentration of Org-P varied between 1.38μmol/g and 5.18μmol/g,accounting for 83.4%–93.4%and 6.6%–16.6%of the TP,respectively.The relative proportions of the five P species followed the order of Det-P>Auth-P>Org-P>Fe-P>Ex-P.On average,Det-P was the major P sink resulted from the atmospheric input and accounted for approximately 58.9%±12.4%of the TP.Auth-P and Org-P comprised 22.8%±11.4%and11.5%±3.0%of the TP,respectively,while Fe-P accounted for 5.1%±2.6%.Lastly,Ex-P comprised 1.6%±0.3%of the ***-P exhibited a negative correlation with Fe-P and Auth-P,while Fe-P showed a positive correlation with Auth-P.This indicated that the formation of Fe-P and Auth-P was at the expense of the regeneration or remineralization of Org-P during early diagenesis.High concentrations of Det-P and Auth-P as well as a low ratio of total organic C to reactive P(TOC/Rea-P)suggested that the aeolian input may play a significant role in sedimentary P budget in the study area.Additionally,well-oxygenated bottom water and low sedimentation rate could be responsible for the low TOC/Org-P ratio in the sediment.

关键词： phosphorus speciation SEDEX sediments western Pacific Ocean

Interannual variations in salt flux at 80°E section of the equatorial Indian Ocean

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中国科学:地球科学英文版 2023年第9期66卷 2142-2161页

作者： Cuncun XIE Ruibin DING Jiliang XUAN Daji HUANG State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Guangxi Key Laboratory of Beibu Gulf Marine Resources Environment and Sustainable DevelopmentFourth Institute of OceanographyMinistry of Natural ResourcesBeihai 536015China institute of Polar and Ocean Technology Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China

The interannual variations in salt flux on the 80°E section in the equatorial Indian Ocean were explored based on the ORAS5 data,which was quite consistent with the observational data among the four available reanalysis datasets.The results indicated that the area with significant interannual variations in salt flux coincided with that of significant climatological mean salt flux in general and was mainly located in the upper 150 m layer.Specifically,three important areas were identified in the north-south direction,i.e.,(1)the Equatorial Indian Ocean Area(EIOA,3°S–3°N),where the mean salt flux was eastward with the largest value on the section and associated with the most significant interannual variations mainly modulated by the Wyrtki Jets and the Equatorial Undercurrent;(2)the South Equatorial Indian Ocean Area(SEIOA,3°S–6°S),where the mean salt flux changed in the vertical direction from strong eastward flux in the upper layer to weak westward flux in the subsurface layer and associated with significant interannual variations in the upper 100 m layer,which was affected by the South Equatorial Countercurrent;and(3)the North Equatorial Indian Ocean Area(NEIOA,3°N–6°N),where the mean salt flux changed in the north-south direction from strong westward flux to the north of 5°N to weak eastward flux in the south and associated with relatively significant interannual variations,which was mainly influenced by the South Sri Lanka Coastal Current.Two leading interannual variation modes were revealed by the empirical orthogonal function decomposition.The first mode accounted for 39%of the total variance and had four significant spatial antinodes;two of those in-phase antinodes were located at SEIOA and upper 75 m of EIOA,and the other two opposite in-phase antinodes were located at NEIOA and below 75 m of EIOA.The second mode accounted for 17%of the total variance having four antinodes with two dominant out-of-phase antinodes located at the subsurface of EIOA and SEIOA.The temporal components of the two leading modes s

关键词： Salt flux Interannual variation 80°E section Equatorial Indian Ocean Current

Reconstruction of large complex sand-wave bathymetry with adaptive partitioning combining satellite imagery and sparse multi-beam data

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Journal of Oceanology and Limnology 2022年第5期40卷 1924-1936页

作者： Huaguo ZHANG Juan WANG Dongling LI Bin FU Xiulin LOU Ziyin WU State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China School of oceanography Shanghai Jiao Tong UniversityShanghai 200240China

Shallow marine sand waves are formed on the seabed and are widely distributed within tidal environments.However,the use of multibeam echo sounding(MBES)is costly to obtain the bathymetric mapping of large complex sand waves.Therefore,we propose a new method that employs a combination of multiangle sun glint images and sparse MBES data to achieve comprehensive bathymetric mapping of large and complex sand waves.This method involves estimating sea surface roughness,automatically extracting sand-wave crests,conducting adaptive subregion partitioning,estimating the water depth at auxiliary points,and generating digital bathymetric models.The method was employed in a case study of sand waves on the Taiwan Bank.Bathymetric mapping was implemented for large complex sand waves over an area spanning approximately 350 km~2 using multiangle sun glint images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer and MBE S data.The results show that mapped and measured water depths were well-matched;the root-mean-square error of water depths was 1.77 m,and the relative error was 5.03%.These findings show that bathymetric mapping of large complex sand waves can be effectively conducted using the new method,and as such,the workload of MBES is reduced and efficiency is improved.

关键词： bathymetric mapping sand waves submarine topography sun glint images multibeam echo sounding(MBES)

Lateral downslope transport and tentative sedimentary organic carbon box model in the southern Yap Trench,western Pacific Ocean

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Acta Oceanologica Sinica 2023年第1期42卷 61-74页

作者： Dong Li Jun Zhao Chenggang Liu Jianming Pan Ji Hu Key Laboratory of Marine Ecosystem Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou310012China

Sediment collapse and subsequent lateral downslope migration play important roles in shaping the habitats and regulating sedimentary organic carbon(SOC)cycling in hadal trenches.In this study,three sediment cores were collected using a human-occupied vehicle across the axis of the southern Yap Trench(SYT).The total organic carbon(TOC)and total nitrogen(TN)contents,δ13C,radiocarbon ages,specific surface areas,and grain size compositions of sediments from three cores were measured.We explored the influence of the lateral downslope transport on the dispersal of the sediments and established a tentative box model for the SOC balance.In the SYT,the surface TOC content decreased with water depth and was decoupled by the funneling effect of the V-shaped hadal trench.However,the sedimentation(0.0025 cm/a)and SOC accumulation rates(∼0.038 g/(m^(2)·a)(in terms of OC))were approximately 50%higher in the deeper hadal region than in the abyssal region(0.0016 cm/a and∼0.026 g/(m^(2)·a)(in terms of OC),respectively),indicating the occurrence of lateral downslope transport.The fluctuating variations in the prokaryotic abundances and the SOC accumulation rate suggest the periodic input of surficial sediments from the shallow region.The similar average TOC(0.31%–0.38%),TN(0.06%–0.07%)contents,and SOC compositions(terrestrial OC(11%–18%),marine phytoplanktonic OC(45%–53%),and microbial OC(32%–44%))of the three sites indicate that the lateral downslope transport has a significant mixing effect on the SOC composition.The output fluxes of the laterally transported SOC(0.44–0.56 g/(m^(2)·a)(in terms of OC))contributed approximately(47%–73%)of the total SOC input,and this proportion increased with water depth.The results of this study demonstrate the importance of lateral downslope transport in the spatial distribution and development of biomes.

关键词： southern Yap Trench sedimentary organic carbon cycling lateral downslope transport diluting effect box model

Microearthquake reveals the lithospheric structure at midocean ridges and oceanic transform faults

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Journal of Oceanology and Limnology 2024年第3期42卷 697-700页

作者： Zhiteng YU Jiabiao LI Weiwei DING Key Laboratory of Submarine Geosciences&second institute of oceanography Ministry of Natural ResourcesHangzhou 310012China

Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the oceanic lithosphere remains poorly understood.The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an indepth view of the underlying detailed seismic structures,contributing to understanding geodynamic processes within the oceanic lithosphere.Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃isotherm.However,this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults.Several mechanisms have been proposed to explain these deep events,and we suggest that local geodynamic processes(e.g.,magma supply,mylonite shear zone,longlived faults,hydrothermal vents,etc.)likely play a more important role than previously thought.

关键词： microearthquake mid-ocean ridge oceanic transform fault oceanic lithosphere thermal structure earthquake location

The bimodality of the Luzon Strait deep water

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Acta Oceanologica Sinica 2014年第5期33卷 17-27页

作者： WU Qingsong ZHAO Jianru ZHANG Junbiao SHI Weiyong LIU Chunqiu Key Laboratory of Engineering oceanography the Second Institute of Oceanography State Oceanic Administration Key Laboratory of Submarine Geosciences the Second Institute of Oceanography State Oceanic Administration State Reasearch Centre for Island Exploitation and Management the Second Institute of Oceanography State Oceanic Administration

Combined conductivity-temperature-depth （CTD） casts and Argo profiles, 3 086 historical hydrocasts were used to quantify the water column characteristics in the northern South China Sea （SCS） and its adjacent waters. Based on a two-dimensional ＂gravest empirical mode＂（GEM）, a gravitational potential （4, a vertically integrated variable） was used as proxy for the vertical temperature profiles TG（P, φ）. φ integrated from 8 MPa to the surface shows a close relationship with the temperature, except in the deep layer greater than 15 MPa, which was caused by the bimodal deep water in the region. The GEM temperature profiles successfully revealed the bimodality of the Luzon Strait deep water, that disparate hydrophic vertical profiles can produce distinct specific volume anomaly （δ） in the SCS and the western Philippine Sea （WPS）, but failed in the Luzon Strait, where different temperature profiles may produce a same 6. A significant temperature divergence between the SCS water and the WPS water confirmed that the bimodal structure is strong. The deepwater bifurcation starts at about 15 MPa, and gets stronger with increasing depth. As the only deep channel connecting the bimodal-structure waters, water column characteristics in the Luzon Strait is in between, but much closer to the SCS water because of its better connectivity with the SCS. A bimodal temperature structure below 15 MPa reveals that there was a persistent baroclinic pressure gradient driving flow through the Luzon Strait. A volume flux predicted through the Bashi Channel with the hydraulic theory yields a value of 5.62×10^6 m^3/s using all available profiles upstream and downstream of the overflow region, and 4.03×10^6 and 2.70×10^6 m^3/s by exclusively using the profiles collected during spring and summer, respectively. No volume flux was calculated during autumn and winter because profiles are only available for the upstream of the Bashi Channel during the corresponding period.

关键词： Luzon Strait historical hydrocasts gravest empirical mode deep water bimodality volume flux