Figure 8

Historical sea level variability, hindcast reef face (sensor C) significant wave height, and daily maximum nearshore (sensor A) sea-swell significant wave height from 1979 through May 2023. (a) Observed sea level relative to mean sea level (MSL, tidal datum analysis period 01-Oct-2011 to 30-Sep-2019) at the Pago Pago tide gauge, courtesy of NOAA. We have highlighted the observed sea level depressions from the strong 1982–1983 and 1997–1998 El Niño events and indicated the magnitude 8.1 Samoa-Tonga Earthquake doublet on September 29, 2009. To highlight the rapid land subsidence following the 2009 earthquakes, vertical land motion from 2001 to present is shown on the right-hand vertical axis, relative to the pre-2009 mean; data courtesy of the Nevada Geodetic Laboratory⁴³. (b) Bias-corrected hindcast reef face (sensor C) significant wave height using hindcasts from Smith et al. (2020)³⁶ and a linear spectral refraction model. (c) Estimated daily maximum nearshore (sensor A) Faga‘itua sea-swell significant wave height based on the nearshore water depth.