Modern sea-level rise breaks 4,000-year stability in southeastern China.

Abstract

Quantifying physical mechanisms driving sea-level change-including global mean sea level (GMSL) and regional-to-local components (that is, sea-level budget)-is essential for reliable future projections and effective coastal management^1,2. Although previous research has attempted to resolve China's sea-level budget from the 1950s^3,4, these studies capture short timescales and lack the long-term context necessary to fully assess modern sea-level rise in southeastern China⁵-one of the world's most densely populated regions with immense socioeconomic importance⁶. Here we show that GMSL followed three distinct stages from 11,700 years before present (BP) to the modern day: (1) rapid early Holocene rise driven by the deglacial melt of land ice; (2) 4,000 years of stability from around 4200 BP to the mid-nineteenth century when regional processes dominated sea-level change; and (3) accelerating rise from the mid-nineteenth century. Our results arise from spatiotemporal hierarchical modelling of geological sea-level proxies and tide gauge data to produce site-specific sea-level budget estimates with uncertainty quantification. It is extremely likely (P ≥ 0.95) that the GMSL rise rate since 1900 (1.51 ± 0.16 mm year^-1, 1σ) has exceeded any century over at least the past four millennia. Moreover, our analysis indicates that at least 94% of rapid modern urban subsidence is attributable to anthropogenic activities, with localized subsidence rates often exceeding GMSL rise. Such concurrent acceleration of global sea-level rise and rapid localized subsidence has not been observed in our Holocene geological record.