TY - JOUR
T1 - A coral microatoll record of sea-level rise, interseismic deformation, and El Niño in La Union, Philippines since 1906 CE
AU - Sarkawi, Gina M.
AU - Meltzner, Aron J.
AU - Peng, Dongju
AU - Lim, Joanne T.Y.
AU - Li, Xinnan
AU - Gautam, Rohan
AU - Gopal, Anandh
AU - Mitchell, Andrew
AU - Sarmiento, Loraine Faye
AU - Weil-Accardo, Jennifer
AU - Maxwell, Kathrine V.
AU - Komori, Junki
AU - Ramos, Noelynna T.
N1 - Publisher Copyright:
© 2025 The Authors
PY - 2025/8
Y1 - 2025/8
N2 - Relative sea level (RSL) along western Luzon is influenced by climate change, tectonic deformation, and the El Niño–Southern Oscillation. Long, high-resolution records of past changes in sea level and land level are crucial to distinguish these contributions for forecasting future RSL or identifying tectonic hazards. Coral microatolls are invaluable proxies for reconstructing RSL, but their interpretation relies on understanding how short- and long-term changes are recorded in the coral skeleton. We analyzed growth bands from 1906 to 2018 CE of a Porites microatoll from Balaoan, La Union, Philippines, using X-rays of vertical cross sections. The microatoll's surface morphology, annual banding, and growth history reveal RSL rise during its lifetime punctuated by 17 diedowns. Coral diedowns generally coincide with low water near the site, often resulting from El Niño events. Excluding eroded sections, 10 of the 11 strongest El Niños since 1918 produced a diedown. Similarly, excluding a diedown caused by the coral tilting, 10 of the 12 preserved diedowns exceeding 3 mm in amplitude occurred during strong El Niños. Between 1948 and 2018 CE, RSL rose at 1.3 ± 1.8 mm/yr (2σ). Comparing sea-level rates from satellite altimetry and RSL from the coral, we estimate vertical land motion at −0.1 ± 12.1 mm/yr between 1995 and 2018 CE. The indicative meaning at Balaoan, defined as the relationship between local water levels and the highest level of growth of a coral microatoll before its most recent diedown, is estimated at 31.5 ± 10.0 cm (2σ) above lowest astronomical tide.
AB - Relative sea level (RSL) along western Luzon is influenced by climate change, tectonic deformation, and the El Niño–Southern Oscillation. Long, high-resolution records of past changes in sea level and land level are crucial to distinguish these contributions for forecasting future RSL or identifying tectonic hazards. Coral microatolls are invaluable proxies for reconstructing RSL, but their interpretation relies on understanding how short- and long-term changes are recorded in the coral skeleton. We analyzed growth bands from 1906 to 2018 CE of a Porites microatoll from Balaoan, La Union, Philippines, using X-rays of vertical cross sections. The microatoll's surface morphology, annual banding, and growth history reveal RSL rise during its lifetime punctuated by 17 diedowns. Coral diedowns generally coincide with low water near the site, often resulting from El Niño events. Excluding eroded sections, 10 of the 11 strongest El Niños since 1918 produced a diedown. Similarly, excluding a diedown caused by the coral tilting, 10 of the 12 preserved diedowns exceeding 3 mm in amplitude occurred during strong El Niños. Between 1948 and 2018 CE, RSL rose at 1.3 ± 1.8 mm/yr (2σ). Comparing sea-level rates from satellite altimetry and RSL from the coral, we estimate vertical land motion at −0.1 ± 12.1 mm/yr between 1995 and 2018 CE. The indicative meaning at Balaoan, defined as the relationship between local water levels and the highest level of growth of a coral microatoll before its most recent diedown, is estimated at 31.5 ± 10.0 cm (2σ) above lowest astronomical tide.
KW - Coral microatolls
KW - El Niño–Southern Oscillation
KW - Philippines
KW - Relative sea level
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U2 - 10.1016/j.margeo.2025.107565
DO - 10.1016/j.margeo.2025.107565
M3 - Article
AN - SCOPUS:105004418891
SN - 0025-3227
VL - 486
JO - Marine Geology
JF - Marine Geology
M1 - 107565
ER -