Bathers at the seawater along the Blekinge and Skåne coasts, but also at Öland's southern tip, have been able to experience cooler temperatures than normal in recent days.
- It has happened due to upwelling.
Colder water from below has mixed up and replaced the warmer surface water on land.
It happened at the Blekinge coast in mid-July, says Mikael Hedblom, marine biologist at SMHI to SVT.
Outside Kristianstad, along Yngsjöstrand, the bathing water temperature has been down to 8 degrees according to measurements by the Norwegian Sea and Water Authority.
Can happen anywhere
An upwelling can occur on all coasts.
When there is an onshore wind, the warm surface water can be transported out from the shore and replaced by colder water that lies further down.
- It is especially on the Blekinge coast because the bay there is quite deep and there can be internal waves further down in the water.
The warm water lies above the cold water.
There the internal waves can arise.
If it blows hard, upwelling can occur, says Hedblom.
According to him, upwelling can occur on all coasts throughout the world.
- If you have offshore wind for a long time and a steep shore at a great depth, then it can happen.
But especially in Skåne, upwelling is unusual.
It's not that deep along the Skåne coast, says Hedblom.