Significant Sea-Level Fluctuations in the Western Tropical Pacific During the Mid-Holocene

Understanding the history of sea-level changes in the past and the associated mechanisms is crucial for predicting sea level in the future. The South China Sea is the largest semi-enclosed marginal sea in the western tropical Pacific. Previous studies showed that this region experienced several sea-level fluctuations up to half a meter on centennial timescales ∼7,000 cal yr BP. These fluctuations were greater in magnitude than the rise in global mean sea level induced by greenhouse effect over the 20th century. However, whether such sea-level fluctuations occurred in a wider temporal context and their potential causes remain unclear. To answer these questions, we reconstructed the mid-Holocene sea-level fluctuations in the northern South China Sea using nine coral microatoll fossils collected from Hainan Island. The results suggest that sea-level fluctuations with amplitude of about half a meter on centennial timescales were common during 6,143–4,384 cal yr BP. Based on recent studies of sea-level driving mechanisms in the South China Sea and paleoclimate reconstructions, we infer that these sea-level fluctuations were likely driven by changes of Walker circulation intensity. Due to the internal variability of the climate system, the possibility of similar sea-level fluctuations in the foreseeable future cannot be ruled out.