High-frequency sea-level analysis: Global distributions

Abstract

This paper provides global climatology of high-frequency (T < 2 h) sea-level oscillations of atmospheric origin. Sea-level series with a temporal resolution of 1 min from 331 tide gauges in the world ocean and spanning between 1.5 and 12 years were analysed to determine the typical ranges, seasons and characteristics of moderate and extreme manifestations of nonseismic sea-level oscillations at tsunami timescales (NSLOTTs). Variances in these oscillations reach 6.6 cm2 on average, but their region-averaged extreme (99.99th percentile) ranges may exceed half a metre or more at individual hotspot locations. The NSLOTTs are the highest in the mid-latitudes and decrease towards polar and tropical regions. Moderate oscillations show clear winter maxima at the majority of stations, while a less pronounced pattern is evident for the most extreme oscillations, which may occur throughout a year. A total of 3080 of the most prominent NSLOTT events were selected from 308 stations and compared to background oscillations, revealing the substantial capability of energy amplification during extreme events. Synchronicity in extreme NSLOTT events between neighbouring stations (up to 250 km) in mid-latitudes has been detected for 20–32% of all episodes, suggesting possible connectivity between the episodes.