The sea level around the coast of Malta and Gozo has gone down by a record-breaking 50cm since January, according to an oceanographer, but this is “nothing alarming” and the waters will rise gradually over the coming weeks.

Extended beaches, bleached seaweed and exposed historical “curiosities” have been observed as a result of the “largest sea level annual anomaly that has been measured on record”.

But Aldo Drago, professor in oceanography at the Malta College of Arts, Science & Technology, put paid to ‘theories’ of tsunamis and recent earthquakes as the cause or effect. 

He explained that this “normal, annual, natural phenomenon” was unrelated to the recent tremors and that the water would continue to rise over the summer to repeat the annual cycle of sea level changes.

Bleached algae that would usually be under water. Photo by Daniel Cilia.

This did not always happen in exactly the same way, Drago said, adding that 2023’s minimum has been “very strong”, decreasing beyond the average of 15cm.

The mean sea level changed over the year and was at a minimum in March and a maximum in November. It was maintained until the following January when it started to fall again, reaching its lowest in March. 

But the intensity and difference between these levels varied from year to year and the most extreme annual change to date was 40cm, recorded between October 1992 and March 1993.

This year, the high sea levels were, on average, maintained until mid-January, until they started on a “very strong downward trend” that is today half a metre below January levels, Drago said.

Sea levels responded to a variety of factors, including tides, surges due to atmospheric pressure and wind setup, as well as coastal seiches.

A strong atmospheric pressure of 1,033 millibars on February 17 would have further accentuated the low levels.

“When this increases, it pushes the sea down,” Drago said, explaining that the atmospheric pressure was not, however, the cause of the current low levels.

These were triggered by the dynamics of the Mediterranean Sea, and in particular density changes due to temperature and salinity, as well as water exchanges with the Atlantic Ocean at the Strait of Gibraltar. 

“It does not mean the sea is not affected by climatic changes,” Drago continued.

“In fact, on top of all these variations, the sea level is also responding to gradual sea level rise, which is measured over a number of years, meaning that sea observations need to be consistent and made at different places.”

No consistent national meteo-marine observing system

Drago has been studying sea levels since 1993, when he set up a network of stations, starting in Mellieħa Bay. 

Today, one in Valletta and two in Marsaxlokk are still operational, using more sophisticated system that provide real-time data.

“However, notwithstanding the importance of sea level data, such measurements do not form part of any consistent and regularly funded national meteo-marine observing system that we direly require to measure and monitor our environment regularly and in real time,” the professor in oceanography said.

Commenting on this year “particularly pronounced” depressed sea level, both in terms of amplitude and temporal extent, marine biologist Alan Deidun mentioned a large area of high pressure over the entire Mediterranean region, kept in place by an even larger region of high atmospheric pressure currently stationed over the north Atlantic.

“This, along with the virtual absence of wind, is translating into depressed sea levels across the breadth and width of the Mediterranean, from the Venice lagoon all the way to Tunisia and Malta,” Deidun said about the link with atmospheric pressure.

Marine species living in the 'intertidal' are accustomed to these fluctuations/excursions, said Deidun, with exposed parts of algae dying off during bleaching or whitening events that have been witnessed in recent days, while motile species can plunge into deeper waters.

“On the other hand, sea level rise is a very real phenomenon, and this is inexorable, unlike the short-lasting dips in sea level that we are experiencing now,” the professor continued.

The dangers of sea level rise, driven by climate change, have been recently raised by Malta at the UN Security Council, given that these pose a security risk by re-drawing maritime boundaries.

Submerged rock bollards from the time of the Knights have been exposed. Photo: Daniel Cilia

‘Historical curiosities’ uncovered

As stretches of coast near the waterline, which were usually underwater, were recently exposed, photographer Daniel Cilia has highlighted a “historical curiosity” in Gozo’s Xwejni Bay that was difficult to shoot because it was always covered with seawater. 

Three man-made rock bollards on the east of the cove were now visible and could have been used to tie a rope, or chains, across to block access to pirate ships in the time of the Knights of the Order of St John, stopping them from sailing in stealthily.

Low levels were also observed in St Paul’s Bay, where the sea in rock pools and around quays decreased significantly, to the point that it would have been hard to moor a small boat.

The difference could have meant that these boats would have hit the bottom as they approached the quay when they previously did not have this problem.

A slipway with usually submerged wooden struts, designed to pull up the boats, was recently exposed, meaning they would have had to be lifted up and out of the water onto the wood, rather than just being easily moved on while still afloat.

Emptying rock pools in St Paul's Bay as the sea level dropped.