The world's only brackish-water archipelago

The seawater in the Luleå archipelago has a very low concentration of salt, i.e., the water is brackish, neither fresh nor salty. Water in the Atlantic is, in fact, ten times as salty. Large volumes of fresh water flow from the great northern rivers into the Gulf of Bothnia, thus diluting the salty seawater.

The inland ice that covered this area about 8,000 years ago formed the landscape in the archipelago that can be seen today. Smooth slabs of bedrock, sand dunes, boulders and moraines all bear witness to the enormous forces of nature.

Land rise (isostatic rebound) - the level of the land is actually still rising after being subject to the enormous weight of the ice layer - is now about 9 millimetres per year or around one metre every 100 years.

The combination of brackish water and land rise (isostatic rebound) has given rise to the special conditions that have influenced natural development in the area. For more than a thousand years, the land rise has greatly affected the lives of the people dwelling in the coastal areas and of those living in the present archipelago. Luleå alone increases in area by 2.25km² every year due to land rise.