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...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.展开更多
Water temperature is one of the most important factors that affect the occurrence of harmful algal blooms(HABs).Characteristics of sea surface temperature(SST)variability related to a Noctiluca scintillans bloom were ...Water temperature is one of the most important factors that affect the occurrence of harmful algal blooms(HABs).Characteristics of sea surface temperature(SST)variability related to a Noctiluca scintillans bloom were analyzed with Himawari-8 data in the Beibu Gulf during mid-February 2021.An SST warming anomaly was found around the bloom area from 10:00 to 19:00 local time,with a peak temperature of 24.3℃at 15:00,which was 2.9℃higher than the surrounding normal sea water.The possible formation mechanism of the HAB-induced SST anomaly was studied in this work by integrating meteorological,ocean dynamics,and ecological processes.During the HAB event,the sea surface was covered by biological mucilage.A model that considered the net heat flux,heat capacity,density of seawater,and temperature variation was established to estimate the thickness changes(ΔH)in the marine heating layer during the HAB event.The model results show that the heating layer thickness of the HAB area(ΔH between 0.76 m and 0.91 m)was smaller than that of the non-HAB area(ΔH>1.19 m).The SST anomaly in this study might be caused by a thinner and warmer marine heating layer that is related to the biological mucilage on the surface of the HAB area.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41876208,41830540,41576174)。
文摘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.
基金supported by the National Nature Science Foundation of China(No.41576175)the Project of State Key Laboratory of Satellite Ocean Environment Dynamics(No.SOEDZZ2202)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311021004).
文摘Water temperature is one of the most important factors that affect the occurrence of harmful algal blooms(HABs).Characteristics of sea surface temperature(SST)variability related to a Noctiluca scintillans bloom were analyzed with Himawari-8 data in the Beibu Gulf during mid-February 2021.An SST warming anomaly was found around the bloom area from 10:00 to 19:00 local time,with a peak temperature of 24.3℃at 15:00,which was 2.9℃higher than the surrounding normal sea water.The possible formation mechanism of the HAB-induced SST anomaly was studied in this work by integrating meteorological,ocean dynamics,and ecological processes.During the HAB event,the sea surface was covered by biological mucilage.A model that considered the net heat flux,heat capacity,density of seawater,and temperature variation was established to estimate the thickness changes(ΔH)in the marine heating layer during the HAB event.The model results show that the heating layer thickness of the HAB area(ΔH between 0.76 m and 0.91 m)was smaller than that of the non-HAB area(ΔH>1.19 m).The SST anomaly in this study might be caused by a thinner and warmer marine heating layer that is related to the biological mucilage on the surface of the HAB area.
