"Since record keeping began in the sixties, we've never encountered anything like this before," ice breaker Ulf Gulldne told the local newspaper Örnsköldsviks Allehanda.
On March 29th, 176,000 square kilometers of the Baltic Sea was covered in ice, a record for the time of year. On a map, it means about half of the central and northern parts are frozen over. Far north, the ice is both thick and difficult to break through.
The date on which the ice reaches its maximum spread usually falls much earlier in the year. The previously latest date record was March 25th, 2008. That year, only 49,000 square kilometeres of the Baltic was covered in ice, which was the smallest maximum spread of ice in the previous 100 years.
"I've never seen this much ice this late in the season," said Karl Herlin, captain of the icebreaker Atle, currently working off the coast of Luleå in northern Sweden.
His crew is freeing up a path through the ice for the ship Rautaruukki that is picking its way to Luleå. It is one of the between five to 15 ships that Atle has assisted every day in the past week, the busiest so far this winter.
"It's kind of cool to see how the weather changes from year to year," Herlin added.
The Swedish Maritime Administration (Sjöfartsverket) has all its five icebreaking crews in service at the moment.
According to the administration's web map of the fleet's activities, the icebreaker Odin is currently leading the way through the ice for eight ships south of Skellefteå. The remaining ice breakers are near Brahestad, Nordvalen and in the bay of Gävle.
"In certain locations the ships need help because the ice has become more compact," Johny Lindvall at the Maritime Administration's ice breaking control room told TT.
Southern parts of the Baltic Sea also retain some ice all the way past Stockholm down to the archipelago outside Västervik.
"The cold is unusually stubborn, as normally the ice would have started to melt by now," said Torbjörn Grafström at the Swedish Meteorological and Hydrological Institute (SMHI).
At first forecasters expected the Baltic ice to reach its maximum in late January, but a prolonged spell of high pressure that arrived over in early March caused new ice to form late in the season, resulting in the record-late date.