BIO-07\INT-08 DS4MES
Remote Sensing of Sea Surface pCO2 Based on a Random Forest Algorithm (RF) in the Yellow Sea
Wei Li* , Marine College, Shandong University, Weihai 264209, China
Chunli Liu, Marine College, Shandong University, Weihai 264209, China
Haijun Ye, Guangdong Key Laboratory of Ocean Remote Sensing, South China Sea Institute of Oceanology, Chinese Academy of Science, Guangzhou 511458, China

Sea surface partial pressure of carbon dioxide (pCO2) is an important parameter in the quantification of air-sea CO2 flux, which further plays an important role in quantifying the global carbon budget. Marginal seas are a dynamic and significant part of the global carbon cycle. However, due to the large temporal and spatial variations of pCO2 and the diversity of control factors in here, there are still large errors in remote sensing estimation of pCO2. In this study, the best estimation model of pCO2 based on different algorithms was established in the Yellow Sea (SYS) from 2011 to 2019, using in-situ data combined with the satellite sea surface temperature (SST), chlorophyll-a concentration (Chl-a), diffuse attenuation coefficient at 490 nm (Kd_490) and salinity (Sal). Spatial and temporal variation of pCO2 were further derived based on the constructed model for the years of 2003–2021. The results showed Random Forest (RF) based pCO2 algorithm had best performance, with root mean square difference (RMSD) of 43.35 μatm, and coefficient of determination (R2) of 0.67, which pCO2 ranged between 290 and 526 μatm. Sal was the most important variable effecting the pCO2 variation in the SYS, followed by the variable of SST, Kd_490, Chl-a. On temporal scale, the pCO2 presented an obvious seasonal with high pCO2 in summer and autumn and low pCO2 in spring and winter. pCO2 showed a rising tendency at a rate of 0.34 μatm per year (R­2=0.27, p<0.05). On spatial scale, pCO2 varied from high value inshore waters to low value in offshore waters, which was consistent with the pCO2 distribution derived with in-situ data.