Remote sensing analysis of spatiotemporal changes in POC sedimentation flux in the South China Sea
This study is based on the monthly particulate organic carbon(POC)flux data of the euphotic layer and ETOPO5 water depth data inverted from MODIS(Moderate Resolution Imaging Spectroradiometer,MODIS)from 2009 to 2018 were used for POC vertical migration formula inversion and empirical threshold linear fitting to present the spatiotemporal distribution characteristics of POC sedimentation flux in the South China Sea from a macro perspective.MATLAB is used for data preprocessing such as synthesis analysis,error analysis and quality control of data,and the Martin curve is compared to carry out correlation verification analysis in non-shore areas(water depth greater than 100 m),and empirical thresholds and linear fitting are used to correct offshore areas(water depth less than 100 m).The results showed that there are obvious seasonal changes in POC deposition flux in the study area.The seasonal average values of POC deposition flux are 13.03 mg C·m-2·d-1 in spring and 14.25 mg C·m-2·d-1 in summer,15.15 mg C·m-2·d-1 in autumn,and 17.99 mg C·m-2·d-1 in winter,with higher values in winter and autumn than in spring and summer.The overall distribution trend is that the POC deposition flux is higher in the insider than the outside of the bay,higher in the near shore than in the ocean basin,and higher in the shallow sea than in the deep sea.When the depth is less than or equal to 50 m,greater than 50 m,less than or equal to 100 m,and greater than 100 m,the average POC deposition flux is 46.39,14.28,and 8.04 mg C·m-2·d-1,respectively.The total POC deposition flux in the study area throughout the year is approximately 19.04(15.72-22.36)Tg C·a-1.These results are of great significance for understanding the carbon storage potential of the South China Sea,and at the same time provide a certain reference for research on blue carbon economic value accounting.
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