The crossing from Stockholm to Turku across the Baltic sea on the 7th of March was like nothing I've ever experienced. Typically 45% of the entire Baltic sea is covered in ice due to the low salinity content of the water.
Two days before several boats, (including the one we were sailing on), became stuck in the ice. Thankfully the passenger ferry with nearly 1,000 people on board returned safely to the Stockholm harbour early Friday after having broken free from heavy pack ice that had trapped it for hours in the Baltic Sea
Dozens of other ships and boats had also been stuck as gale-force winds built up large ice masses along the Swedish coastline.
Ice breakers helped release the ferry Amorella at the edge of an archipelago north of Stockholm. Rescue helicopters and military hovercraft had been placed on standby to evacuate passengers if needed. No one was injured.
The flow of fresh water into the sea from approximately two-hundred rivers and the introduction of salt from the South builds up a gradient of salinity in the Baltic Sea. Near the Danish straits the salinity is close to that of the Kattegat, but still not fully oceanic, because the saltiest water that passes the straits is still already mixed with considerable amounts of outflow water. The salinity steadily decreases towards North and East. At the northern part of the Gulf of Bothnia the water is no longer salty and many fresh water species live in the sea. The salinity gradient is paralleled by a temperature gradient. These two factors limit many species of animals and plants to a relatively narrow region of Baltic Sea.
Music: "Midnight Walker" by Davy Spillane