Attribution of annual maximum sea levels to tropical cyclones at the global scale

Long-term global coverage of historical 6-h best track tropical cyclone (TC) records and hourly sea-level time series are used to examine the relative TC contribution to annual maximum sea levels (AMSLs). Analyses are performed at 177 tide gauge (TG) stations with at least 25 years of complete data since 1970. We associate an AMSL (before and after removing the astronomical tide) with a TC if the centre of circulation of the TC passed within a given distance from the station and a given time window. Spatial and temporal sensitivity analyses are performed with varying time windows (±6 and ±12 h) and buffer radii (400 and 500 km) around each TG station. Results indicate that TCs play a prominent role in determining the spatial distribution of sea-level maxima in active TC regions, with some locations experiencing more than 75% of annual maxima due to these storms. The fraction of TC sea-level maxima is particularly high along the coasts of Taiwan, southern China, the Philippines, the eastern United States, the Gulf of Mexico, the Bay of Bengal and western Mexico. Analysis of nontidal residual maxima (the total sea-level signal minus the harmonic tidal contribution) reveals an increase in the measured fractions of sea-level maxima attributed to TCs in the majority of the stations. These results further support the notion that TCs are responsible for major extreme sea levels and indicate the notable influence of tides on AMSLs. Given the major role that the El Niño–Southern Oscillation (ENSO) plays in TC activity, we also examine the relationship between TC-driven extreme sea levels and ENSO using logistic regression. We identify regional differences in the link between ENSO and TC-induced AMSL, with higher probabilities of TC-induced AMSL during La Niña in the North Atlantic, and during El Niño in eastern Asia.