Abstract
Vertical land motion at tide gauges influences sea level rise acceleration; this must be addressed for interpreting reliable sea level projections. In recent years, tide gauge records for the Eastern coast of Korea have revealed rapid increases in sea level rise compared with the global mean. Pohang Tide Gauge Station has shown a +3.1 cm/year sea level rise since 2013. This study aims to estimate the vertical land motion that influences relative sea level rise observations at Pohang by applying a multi-track Persistent Scatter Interferometric Synthetic Aperture Radar (PS-InSAR) time-series analysis to Sentinel-1 SAR data acquired during 2015–2017. The results, which were obtained at a high spatial resolution (10 m), indicate vertical ground motion of −2.55 cm/year at the Pohang Tide Gauge Station; this was validated by data from a collocated global positioning system (GPS) station. The subtraction of InSAR-derived subsidence rates from sea level rise at the Pohang Tide Gauge Station is 6 mm/year; thus, vertical land motion significantly dominates the sea level acceleration. Natural hazards related to the sea level rise are primarily assessed by relative sea level changes obtained from tide gauges; therefore, tide gauge records should be reviewed for rapid vertical land motion along the vulnerable coastal areas.
Highlights
Sea level rise (SLR) is a global phenomenon that threatens low-lying coasts and islands [1]
In delta regions or basins, the relative sea level is often dominated by subsidence due to both long-term glacial isostatic adjustments (GIA) and recent compaction of deltaic sediments due to natural and anthropogenic processes
For vertical ground motion at tide gauge sites, few attempts have been made to attribute the dominance of the local subsidence rate, as tide gauges around the world are not always equipped with global positioning system (GPS) instruments [26,27]
Summary
Sea level rise (SLR) is a global phenomenon that threatens low-lying coasts and islands [1]. In addition to the T/P and Jason satellites, the successors of these kinds of satellites, such as ERS-1 & 2, SARAL/Altika, Cryosat, HY-2A, and Sentinel-3 a/b have provided global and regional sea level records for the past 25 years that allow us to detect spatiotemporal variations [13]. These long-term altimeter records are calibrated with the tide gauges to provide accurate sea level records. For vertical ground motion at tide gauge sites, few attempts have been made to attribute the dominance of the local subsidence rate, as tide gauges around the world are not always equipped with global positioning system (GPS) instruments [26,27]
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