Figure 2
From: Late Holocene relative sea-level records from coral microatolls in Singapore
Coral microatoll growth tracks relative sea-level change. (a, b) Photographs of a living Porites sp. microatoll at Siloso Point, documented in year 2020 within 1–2 months of a ~ 7 cm diedown. (c–e) 3D schematic (top) and cross-sectional radial profiles (bottom) showing the coral microatoll HLG tracking (c) stable, (d) rising and (e) falling relative sea level. In (c)–(e), we show only every 4th annual band of each radial cross section for clarity. Each black tic mark at the bottom of (c)–(e) represents a year. The blue curves (middle) show changes in the lowest annual tide from year to year and represents the theoretical HLS that the coral can grow up to. Each time the coral HLG catches up to the lowest tide, a diedown occurs (red dot). Consecutive diedowns occur in years when the lowest annual tides get progressively lower. For simplicity, we label each cluster of diedowns collectively as one diedown (numbered); in the radial cross sections (c–e, bottom panels), we show only the lowest diedown in each cluster of diedowns for clarity. These labelled diedown clusters are ~ 18.61 years apart and are modulated by the lunar nodal cycle38. HLS: highest level of survival; HLG: highest level of growth. 3D coral microatoll schematics in (c)–(e) were developed using the 3D coral microatoll simulator of Ref.83.
