Spatiotemporal Changes of Ocean Heat Content in the Seas around China

Ocean Heat Content (OHC) is vital for understanding climate change, as over 90% of the Earth’s Energy Imbalance is stored in the ocean. Previous OHC studies have focused on global and basin-scales, but changes and their variability in the seas around China (SAC) remain unclear. This study investigates OHC changes in the SAC, including the Southern Yellow Sea (SYS), East China Sea (ECS), and South China Sea (SCS), using the 4th version of gridded observational datasets developed by the Institute of Atmospheric Physics. From 1960 to 2023, OHC in the upper 2000 m of the SAC has increased by a rate of 0.15 ± 0.05 Wm-2. SCS exhibits the highest OHC 0-2000 m growth rates at 0.18 ± 0.04 Wm-2, while the SYS showed the smallest heat accumulation at 0.05 ± 0.01 Wm-2. Seasonal analysis revealed that the spring OHC increasing is the highest at 0.18 ± 0.05 Wm-2. On the inter-annual scale, SAC OHC negatively correlates with the El Niño–Southern Oscillation index (R = -0.77), especially in the SCS (R = -0.79). On the decadal scale, SAC OHC significantly correlates with the Interdecadal Pacific Oscillation index (R = -0.76) from 1980 to 2023. The documentation of the OHC change on seasonal to decadal scales in this work provides an observational basis for future understanding of the mechanisms and model evaluation.