Disentangling vertical land motion and waves from coastal sea level altimetry and tide gauges

In the context of global mean sea level rise, understanding the drivers of relative sea-level (RSL) at the coast is of major importance for coastal environments research and management. Since the 1990s, the combination of satellite altimetry observations with in situ tide gauge data has provided a better understanding of coastal sea level variability, but challenges remain to quantify the relative contributions of possible drivers (oceanic, vertical land motion (VLM), atmospheric and wave). Here, over the period 1993-2015, we combine concurrent observations from satellite altimetry, tide gauges, and oceanic model hindcast in order to identify the predominant drivers responsible for long-term variability of RSL at 434 coastal locations worldwide. We found that the dominant driver of the RSL trend is the ocean components in 76% of the cases, VLM in 17% and waves in 7%. Interestingly, no significant trend in the wave setup was noted over the period considered at most of our coastal stations. However, at some locations, we found significant correlations between the wave setup hindcasts and VLM data. Moreover, we evidence a substantial variance reduction in the VLM once corrected for the wave setup. We therefore recommend future studies aiming at VLM estimation to consider applying wave setup corrections to improve the comparability of the tide gauge and satellite altimetry measurements.

Automated summary

In this study, the dominant driver of global RSL trends was found to be the ocean components in 76% of cases, with VLM and waves contributing to the variability as well. Significant correlations were observed between wave setup hindcasts and VLM data at certain locations, highlighting the importance of wave setup corrections for VLM estimation in future studies.