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 similar to 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. Microatolls on Hainan Island revealed multiple half-meter sea-level fluctuations on centennial timescale during the mid-Holocene These sea-level fluctuations are similar to those occurred similar to 7,000 cal yr BP in other regions of the South China Sea The responsible mechanisms were likely related to the changes of the Pacific Walker circulation intensity