Anthropogenic effects on tropical oceanic climate change and variability: An insight from the South China Sea over the past 2000 years

Abstract

Abstract To better understand the effect of human activities on tropical oceanic climate change, existing coral-based paleoclimate data from the northern South China Sea (SCS) for several representative climate periods over the past 2000 years were synthesized and reanalyzed. The sea surface temperature (SST) during the current warm period (CWP), in which the climate has been influenced by human activities, exhibits larger change amplitude and higher oscillation frequency than during periods in which the climate was controlled by natural forcings. However, the variabilities of the sea water δ18O (δ18Osw) during the four climate periods over the past 2000 years examined here are somewhat complicated to decipher. The variation amplitudes are variable but the interannual oscillations are similar during different periods. Even so, high variability during the CWP may still suggest the anthropogenic effects on tropical oceanic hydroclimate. This may implies that the anthropogenic effects intensify the tropical SST and hydrological variation both in amplitude and frequency. The decoupling between coral δ13C and total solar insolation during the CWP may be a result of the oceanic δ13C Suess effect from the addition of anthropogenic 12CO2 to the surface ocean. This suggests that increased anthropogenic CO2 caused the main carbon source and the utilization process of coral reefs during calcification to change. To accurately assess the influence of human activities on oceanic climate and environmental change, the effects of anthropogenic CO2 should be monitored continuously over a longer time frame.