On the snowy shore of the northern Swedish city of Luleå, bathers are lowering themselves into a rectangular hole in the frozen seawater. "It's like a happiness rush afterwards," says Katariina Yliperttula, 44, who is taking a dip before work. While many have their own hobbies that keep them going through the cold dark winter months here ice swimming, cross-country skiing, walking on the "ice road" out into the archipelago " one thing remains a problem: loneliness. In an attempt to counter that, authorities in Luleå have launched a campaign to ease that social isolation, ever so slightly, by encouraging people to say hello to one another. The Säg hej! (say hello!) campaign says it aims to create a friendlier city by nudging people towards small but significant social interactions. Adverts are running on buses, and workshops are being held in schools. Recent research found that among 16- to 29-year-olds, 45% of people in Luleå were experiencing problems as a result of loneliness. Åsa Koski, who works for Luleå municipality, came up with the idea for the campaign. She wants the city, which is undergoing a period of rapid growth as it tries to attract tens of thousands of new people to work in "green" industry ... to not grow more atomised as a result. "We don't just want that Luleå is going to grow as a city; we want Luleå to be a pleasant and safe and friendly city," says Koski. Being greeted by strangers makes people feel "more seen and a bit more like you belong", she adds.