Residents of Marsascala and St Julian's woke up to a strange phenomenon on Thursday morning as the sea levels suddenly dipped, then rose again, beyond the usual shoreline, flooding promenades in the process.
They were witnessing a phenomenon known as a coastal seiche, or milgħuba, caused by a sudden atmospheric change. The event is also referred to as an “athmospheric tsunami” but is in no way a tsunami.
Martina Gatt from the Malta Meteorological Office explained that the Luqa barometer measured a 3 millibar change in air pressure that happened in the space of an hour, early in the morning.
The air pressure pushes down on the sea, like a giant weight, causing water to retract from the shore as it moves towards the dip, then back to shore as it settles back into place. This creates an oscillation that continues until the water settles back in place.
“Sometimes, as the water re-enters, it goes to a higher level than before. This usually settles in a few hours and, in some cases, it takes a few days,” she said, noting that this gentle movement of water was “not uncommon” and impacted low-lying areas where it was more visible.
Spinola Bay, located between Sliema and St Julian’s was one of the low-lying areas impacted. Frances Grech was in her home, overlooking Spinola Bay when at about 7am she heard a hissing sound of water and looked out of her balcony.
“I saw that the promenade was wet. At first I thought they had washed it. Then I saw the tide come in, then head out again. It did this about three times. I’ve seen this before,” she said, wondering if it posed a threat to anyone swimming at the moment it happened.
One woman experienced exactly that. Commenting on a closed Facebook group, she wrote: "This morning at 7am I had a weird experience while swimming in Balluta. The level of the sea fell down so quick, almost 2 metres and went up again to a high level. There were also currents which was difficult to swim. It kept doing it for almost an hour."
The coastal seiche was also witnessed at about 7am by Stephen Bell who was walking his dog in Marsascala. A video he posted on Facebook showed exposed parts of the seabed as the water levels dipped.
This is not the first time that Malta experienced this phenomenon. In 2019, an atmospheric tsunami struck Malta’s east coast sweeping small boats onto the rocks in Xemxija. This also happened in 2014 when the “mini tsunami” washed over low-lying areas, as well as in 2012.