[A-OS13] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS13-P06] DINEOF data interpolation and EOF analysis of YOC chlorophyll a in the Yellow and East China Sea from 1998 to 2021

*Haoran Zhang¹, Genki Terauchi², Elígio de Raús Maúre², Joji Ishizaka³ (1.Graduate School of Environmental Studies, Nagoya University, 2.Northwest Pacific Region Environmental Cooperation Center, Japan, 3.Institute for Space-Earth Environmental Research, Nagoya University, Japan)

Keywords:Chlorophyll a, East China Sea, YOC algorithm

The Yellow and East China Seas (YECS) are marginal seas surrounded by China, Japan and Korea. Phytoplankton is the most important aquatic primary producer and plays an important role in the marine ecosystem in the YECS, and the total abundance of phytoplankton is usually indicated by chlorophyll-a (chl-a). To better understand the complex variability of chl-a in the YECS, we used an improved chl-a product (Yellow Sea Large Marine Ecosystem Project Ocean Color product; YOC) for more than 20 years calculated by Northwest Pacific Region Environmental Cooperation Center (NPEC). The YOC eliminated chl-a overestimation in turbid water in YECS comparing with the standard algorithm. Data Interpolating Empirical Orthogonal Function (DINEOF) was used for interpolating the missing monthly chl-a data and Empirical Orthogonal Function (EOF) for delineating the seasonal variability of chl-a in the YECS. The time period in our research is from January 1998 to December 2021 and the research area is from 30° to 41°N and 117° to 131°E. Our results showed the first three mode of EOF by the spatial pattern and time coefficient of the variability of chl-a and the first three modes of EOF accounted for 48.12% of the total variance. The first mode of EOF (32.31%) revealed the high variability of chl-a in the middle of Yellow Sea, the offshore area of Changjiang estuary and the western part of the Sea of Japan. The positive phase peaked in April and May while the negative phase peaked in July and August. This EOF mode may be controlled by the spring bloom and the Changjiang river discharge. The second mode of EOF (9.77%) revealed the high variability of chl-a in the -south and southeast coast of the Jeju Island and Korean Peninsula. This EOF mode may be controlled by the wind-induced upwelling. The positive phase peaked in May and August while negative phase peaked in July. The third mode of EOF (6.04%) revealed the high variability of chl-a in the offshore region of the Changjiang estuary. The positive phase peaked in July while the negative phase peaked in September and October. The first three modes of EOF all showed the strong seasonal variability of chl-a in the YECS.