The Finnish Metereological Institute is warning of deceptively weak ice conditions on Finland’s waterways. The thickness of ice cover is no longer a reliable indicator of its safety, because as soon as the ice begins to darken in the spring melt, it is time to stop walking on it.
If there is no alternative but to travel across the ice, it is strongly advised to carry ice picks. Sea ice is particularly dangerous in the warmer spring temperatures, as rock formations under the surface affect the ice’s stability. Sea ice as thick as 30 centimetres can be unreliable to walk on.
“Ice that was safe to walk on in the morning can become unsafe in a few hours,” says ice expert Jouni Vainio from the Metereological Institute. “In the spring you can never be sure where the ice is safe and where it isn’t.”
According to Vainio, dark ice is always unreliable, while even white ice can spring surprises on the unwary. Sea ice is deceptive because it is also heated from below. Currents bring very localised melting that could cause weak ice just ten metres from ice that is safe to walk on.