Explore Sweden’s largest underwater cave system »Explorersweb
In 2007, a group of cave divers began probing an underwater cave in central Sweden’s Jämtlandsfjäll. When they started, they had no idea that they would discover Sweden’s largest underwater cave system. Fifteen years later, they are still exploring it. They were there last week.
Cave diving is notoriously dangerous. The hand-picked team of 20 managed to cope with deep snow, ice and minus degrees. And that was even before you went into the cave.
Their 13th expedition into the caves began on March 25. The only years they did not go were the pandemic years 2020 and 2021. This year they were divided into two teams and focused on separate caves: Bjurälvsgrotten and Festins.
Every winter, the challenges are similar. The first is just to get to the flooded caves. No roads or villages are nearby. They need a scooter to northwest Jämtland. They only dive in the winter because vehicles at other times of the year are prohibited to preserve the fragile vegetation of this national park. In addition, the current through the caves is too strong in the summer.
Once they get there, they must first shovel out meters of snow, plus debris from the previous summer, which blocks the entrance. Then they do reconnaissance dives to set up equipment and spare oxygen tanks in the areas they have already mapped.
The entrances to the caves and the passages inside are so narrow that the equipment must be mounted sideways. The cave system has many swamps. Swamps are flooded areas in the cave that make exploration of dry caves impossible. As of 2016, they dived in Sump 5.
When swamp diving, cavemen must navigate narrow passages and vertical falls, often crawling and dragging equipment while carrying diving-type equipment. They have to climb, rappelling and rig traction systems underwater. The water temperature is around 0 ° C, so all divers wear dry suits. Dry suits are not known for their streamlined nature.
On the third day of this year’s expedition, the teams entered both caves. Bjurälvsgrotten had a much more challenging entrance. Each diver had to make a 10 m vertical descent inside a waterfall before being disconnected from the ropes. Once inside, they needed the shovel to improve accessibility.
Throughout the week-long expedition, diving at Bjurälvsgrotten was a struggle due to the strong flow even at this time of year. They were more successful in Festins. After five days, they discovered the virgin caves and were able to complete 30 meters of examined line.
“Thirty meters does not seem like much,” they explained, “but it requires quite a lot of effort [to map] every meter of virgin cave. “
They then examined another 30 meters of line. At the end of their expedition, both teams made a preliminary dive at the Meander Cave, the Bjurälven’s lowest known outlet. They hope to explore that region further in the future.
Expedition Bjurälven is named after Bjurävlendalen where the exploration is taking place. The whole region is flooded with caves. For many caves, data on explorations go back to the middle of the 20th century. Researchers with the expedition believe that all caves in the area can connect to a giant cave system.
So far, their theory has stood firm. So far, they have discovered 2.43 km of interconnected passages and caves, which makes it the longest underwater cave in Sweden. No one knows how much longer it extends. Finding out is a job for many years to come.