Kim, K.; Shin, J.; Kim, K.Y., and Ryu, J.H., 2019. Long-term trend of green and golden tide in the eastern Yellow Sea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 317-323. Coconut Creek (Florida), ISSN 0749-0208.
Since 2008, floating green tides (Ulva sp.) have been occurring continuously in the Yellow Sea (YS), and after 2013 floating golden tides (Sargassum sp.) have also occurred. The distribution, areal coverage, and migration of floating green tides have been actively studied, but most research has focused only on the western YS. Little is known about the floating golden tides in the eastern YS. The purpose of this study was to determine the long-term distribution of floating green and golden tides in the eastern YS using Geostationary Ocean Color Imager (GOCI), Moderate Resolution Imaging Spectroradiometer (MODIS), and Landsat satellite images from 2008 to 2017. In addition, the migration of floating macroalgae with Global Hybrid Coordinate Ocean Model (HYCOM) surface current data were compared. Green tides were observed in 2008, 2009, 2011, 2015, and 2016 in the eastern YS. From a satellite image backtracking analysis, it was confirmed that the green tides observed in the eastern YS were supplied from the western YS. When the maximum areal coverage of green tide was compared between the eastern and western YS, the coverage in the eastern YS was found to be about 4 % of that of the western YS. However, in 2011, the largest amount of floating macroalgae was found in the eastern YS and it accounted for about 45 % of the amount in the western part of the YS. In the eastern YS, floating golden tides were found in 2013, 2015, 2016, and 2017, with the largest amount of floating macroalgae occurring in 2017. Although there were no long-term golden tide data for the western YS, such that it was not compared to the areal coverage of the eastern YS, it was confirmed that the amount of golden tide supplied to the eastern YS gradually increased. A comparison between the migration of floating macroalgae and HYCOM surface current data suggested that the migration and flow directions were not identical, and were considerably affected by surface ocean currents during their passage into the eastern YS. From this study, the long-term distribution and changes in areal coverage of green and golden tides in the eastern YS were obtained for the first time. This information will be useful for understanding the long-term patterns of green and golden tides, and provides basic data for predicting the occurrence and migration of floating macroalgae.