2026 has started with more than one record being broken in Estonia, all relating to winter: January brought the lowest temperatures seen in a quarter of a century, electricity prices reached new highs even in comparison with the already high prices of recent years, and now the sea around Estonia, especially to the west, may reach its lowest level since records began.

The low record for this century is -67 cm, in other words 67 cm below the mean level, set in 2010, but concerns are that the water level will fall further. The problem mostly affects the more enclosed west coast, where the bulk of Estonia's populated islands are located.

The water level drop so far has already wreaked havoc for shipping: The Regula, a ferry which serves Hiiumaa, ran aground briefly twice on Tuesday morning, and other routes have been affected too.

In the Suur Strait, for example, which separates the mainland from the island of Muhu, and the adjacent Saaremaa, there is still enough water between the bottom of a ship's hull and the seabed, but there is no margin for any further fall before even worse problems can hit the Hiiumaa ferry link in particular.
The route is longer than that between the mainland and Saaremaa, and also has not fully dredged channel.

"With their full draft, which is several meters, [ships] can operate down to a water level of -57 cm. If it drops below that, then accordingly they can no longer take on a full load," said Janis Osa, harbor master at Kuivastu, Muhu's ferry port.

Märten Kraav, captain of the Piret ferry, which serves Muhu/Saaremaa, noted other factors. "The speed difference, meaning that when a ship is moving, its draft increases further. If the draft is four meters when loading and leaving the harbor, the reality is that once it starts moving, the faster it goes and at the same time the narrower the shipping channel, the deeper it sinks. It can sink by up to nearly half a meter," he said.

In Kuivastu harbor, the shallow sea affects both boarding and disembarking.

"The water level was 60 cm above zero when the water began to freeze, or froze over. As of today, when it was last at -62, it has dropped 120 cm since the moment it froze," Osa added.

Loading a ship in the current conditions is, in the Piret captain's words, a kind of balancing act.

"If you load some heavy object onto the ship, at the first moment when it drives onto the vessel, it pushes the bow down. But when it moves to the other end, then on the contrary, it pushes that end down and lifts the bow up. You constantly have to take such nuances into account, whether to load the next item at the same time," Kraav said.

Once on Muhu, reaching Saaremaa is simpler, as the two islands are connected by a causeway road.

In the worst case scenarios, vehicles may need to be restricted to keep the ferries running, and even pedestrians too, with the vessels solely used for transporting essential supplies. That stage has not been reached yet on Hiiumaa or most other islands, though inhabitants of Ruhnu, much further out to sea in the Gulf of Riga, say they are cut off from the mainland, with supplies dwindling.

As for the causes of the low water levels, the formation of ice, though it too has caused problems for ships in becoming compacted, is not the main culprit. Tallinn University of Technology's (TalTech) Meresüsteemide instituut had the real reason.

"There is a strong high-pressure system over the Baltic Sea, which essentially pushes the water into the North Sea, where there is a low pressure [zone]. According to the law of communicating vessels, water moves to where there is less resistance," said Rivo Uibopin, the marine institute's director.

This high pressure area is blocking off lows in the region too, meaning the situation may prevail for days to come, and consequently a further fall in the sea level.

"There is a chance that this value will be exceeded. In Virtsu it was -62 cm today and that record was -67 cm. The forecast models extend to February 9–10, and according to them the sea level will remain under -50 centimeters," Uibopin said.

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