Abstract
Changes in the seasonal sea level cycle (SSLC) can modulate the flooding
risk along coastlines. Here, we use harmonic analysis to quantify
changes in the amplitude and phase of the annual component of the sea
level cycle at 663 tide gauge locations along the global coastline where
long records are available. We identify coastal hotspots by applying
clustering methods revealing coherent regions with similar patterns of
variability in the annual sea level cycle (ASLC). Results show that for
most tide gauges the annual amplitude reached its maximum after 1970 and
its peak typically occurs during the fall season of the respective
hemisphere. Many tide gauges exhibit non-stationarity in the annual
cycle in terms of amplitude and/or phase. For example, at 125 tide
gauges we find significant trends in the amplitude (either increasing or
decreasing) while several sites (36 in total), mostly in the
Mediterranean and around Pacific islands, experienced phase changes
leading to shifts in the timing of the peak of the annual cycle by more
than a month. Our results highlight the importance of accounting for
potential non-stationarity in seasonal mean sea level (MSL) cycles along
coastlines.