Several harbours in the western Mediterranean, including Portocolom, Puerto Soller and Porto Cristo, have been flagged as newly vulnerable to meteotsunamis, according to research conducted by the University of the Balearic Islands (UIB) and the Spanish Institute of Oceanography (IEO). These sudden, atmospheric-induced sea level surges, known locally as 'rissagues', have long been overlooked outside well-known sites such as Ciutadella. The study provides the first regional analysis of these phenomena, highlighting additional ports such as Vilanova i la Geltrú and Sant Antoni, which had previously received little scientific attention.
The investigation draws on 17 years of high-resolution observations from 27 coastal monitoring stations across the Balearic Islands and Spain’s northeastern coastline. Researchers found that the intensity of meteotsunamis is highly variable, largely shaped by the geometry and depth of each harbour. Unlike traditional tsunamis triggered by seismic activity, these waves result from rapid atmospheric pressure changes. While often small in open waters, the waves can resonate within shallow continental shelves and confined harbours, sometimes exceeding one metre in height, capable of flooding quays and damaging coastal infrastructure.
The newly identified sites have already shown significant sea level variations. Measurements indicate that atmospheric disturbances, when combined with the natural resonance of each port, can generate waves over one metre high. Yet, Ciutadella remains the most prone to meteotsunamis, both in frequency and amplitude. Larger harbours, such as those in Barcelona, Tarragona, Palma, and Valencia, appear relatively insulated from such events due to their depth and broader shapes, which dampen resonance effects.
Interestingly, the study reveals that meteotsunamis are often regional rather than localised events. Data from l’Estartit in Girona suggest that 88% of recorded episodes coincided with noticeable sea level fluctuations in neighbouring ports. Researchers attribute this simultaneity to atmospheric wave patterns that are most common in spring and summer, capable of influencing vast stretches of the western Mediterranean. Exceptions occur in places such as Alcudia Bay, where meteotsunamis have also been recorded during winter, triggered by cold fronts or severe storms.
The study relied on an extensive network of tide gauges, providing minute-by-minute sea level data for both the Balearics and eastern Spanish coast. These include sensors operated by Puertos del Estado since 2006, the Sistema d’Observació Costanera de les Illes Balears (SOCIB) from 2011, and the PortsIB gauge at Ciutadella installed in 2014. More recently, the VENOM network, a collaboration between UIB and IEO-CSIC, deployed nine low-cost sensors since 2020, enhancing spatial coverage. Long-term amateur data from Josep Pascual in l’Estartit, recording sea levels every minute since 2006, was also incorporated.
One researcher involved in the study described the findings as “pioneering work that consolidates the UIB’s position as an international reference in tsunami studies.” The team emphasised the need to expand high-frequency monitoring networks to better understand meteotsunamis, which, despite often occurring under seemingly calm conditions, pose a tangible risk to Mediterranean coastal communities. The insights gained are expected to guide future monitoring and mitigation strategies for ports and infrastructure exposed to these sudden, sometimes destructive, sea surges.