We are not safe! Past events are evidence that the Mediterranean Sea is not spared from large tsunamis, and the Maltese Islands can face such seismic generated devastating sea waves especially from its eastern approaches. Severe wind and adverse weather conditions are often accompanied by deep lows in atmospheric pressure to which the sea responds with a rise in level (storm surge) providing a sort of barrier wall to storm water flow into the sea, leading to flooding like that we often experience in Msida.

Flooding of coastal areas can however also occur when it is least expected during calm weather due to a phenomenon known as the 'Milgħuba', often referred to as a meteo tsunami, consisting of large and rapid sea level fluctuations occurring over a span of a few minutes and triggered in such cases by atmospheric gravity waves. Besides these transient phenomena, sea level monitoring is also important to assess climatic changes, but with a firm commitment to long-term data acquisition. 

It is therefore not surprising that the history of the PO-Unit, now the Physical Oceanography Research Group (PO.Res.Grp), indeed started in 26 years ago, more precisely in May 1993, with a sea level gauge installed in Mellieħa Bay, the first digital sea sensor measuring sea level fluctuations at an unprecedented frequency of 30 records every hour and permitting the sea level variability in the Maltese Islands to be assessed with precision and long-term datasets. In 2001, a new more sophisticated sea level gauge was set up in Portomaso where it still continues to transmit valuable data in real-time (meteo-marine observations on www.capemalta.net). 

A new gauge has recently been added, at a station within the premises of Paradise Bay Resort at Cirkewwa, to measure sea level variability for the first time on the southern coast of Malta. The position of the Maltese Islands at the edge of the continental shelf that connects the archipelago to the Sicilian mainland presents an ideal oceanographic case, mimicking a permanent research vessel, to study some still unresolved dynamical features pertaining to this sea domain, like shelf oscillations and topographically trapped waves that both produce a significant signature on the sea surface movements.             

The Cirkewwa IDSL station monitors sea level fluctuations by a microwave sensor mounted above the sea surface, measuring the distance of the air gap between the sensor and the sea.

This installation matured from collaboration between the Joint Research Centre of the European Commission (JRC) and the PO.Res.Grp with the coordination of Prof. Aldo Drago who leads sea level assessments at the University of Malta. Dr Adam Gauci is responsible for the observing system of the PO.Res.Grp within the Department of Geosciences, and executed the installation of the new gauge with the support of Dr Alessandro Annunziato from JRC-Ispra.

The measuring device consists of an Inexpensive Device for Sea Level (IDSL) mounted above the sea, measuring the distance of the air gap from the sea by means of a microwave sensor. Data logging is made by a Raspberry Pi computer with a sampling interval is 15 s, and data transmission by GSM every minute to a server where it is stored, quality controlled, and prepared for online visualisation. The station is powered by a solar panel, and batteries that can provide an autonomy of seven days.

Like the station in Portomaso, this new station forms part of the Tsunami Warning and Mitigation System (NEAMTWS) established under the Inter-Governmental Oceanographic Commission (IOC) of UNESCO. This effort will soon extended by a third station in Marsaxlokk, thus increasing the number of real-time stations maintained by the PO.Res.Grp to a total of three. This sea level network is a building block for the national tsunami alert system that the Civil Protection Department is planning to deploy.  

The marine observation team of the PO.Res.Grp collaborates with a number of international groups and is constantly working to add, upgrade, and improve the national meteo-marine data acquisition system for the Maltese Islands. Besides sea level data, an HF Radar system for the real-time monitoring of sea surface currents has been set up and is currently being extended within the current CALYPSO South project that is partially funded by the Interreg V-A Italia-Malta Operational Programme. In collaboration with Transport Malta, seven new meteo stations are planned to be installed early next year in major ports for ship navigation and safety.

More information on the research activities is available at www.capemalta.net.