Water level

The expected sea level change will affect the Swedish coast in different ways. The water level in Swedish lakes will change as well. Some will see an increase and others a decrease, varying between different lakes and also between different seasons. 

Many processes affect the water levels along our coasts and in our lakes. For the sea this could be water temperature, wind, air pressure and post-glacial rebound. The lakes are affected mostly by rainfall, snowmelt and water regulations.

Rising sea levels

During the last century, the sea level has risen at a rate that has nearly doubled in the last 20 years.

In September 2013, the IPCC presented the first part of the fifth assessment report. It included a large number of calculations of sea rise by the end of the century with the reference period 1986-2005.

For an alternative with high emissions of greenhouse gases an interval of 52-98 cm has been specified, which agrees reasonably well with the assessment that has been applied in Sweden so far. What is also highlighted is that the ocean will likely continue to rise long after the year 2100.

Post glacial rebound or land subsidence affects the local effects of rising seas. The land uplift means that the local sea level rise will be lower in the central and northern parts of Sweden, while Skåne in southern Sweden cannot take advantage of this effect.

Stockholms havsvattenståndsserie
The Stockholm sea level series is one of the longest sea level records in the world. In the series, the on-going sea level rise is inferred. The figure shows the annual mean for sea level in Stockholm since 1774. The sea levels rise since the late 1800s emerges as the deviation from the regression line that reflects land uplift. Enlarge Image
The figure shows the net effect of sea level rise minus land uplift along the coast of Sweden, subject to a global sea level rise of 1 metre in 100 years. The calculation of uplift is based on the Swedish National Land Survey uplift model NKG2005LU. Enlarge Image

Water levels in lakes

What mainly controls the water level in the lakes is the amount of inflow and outflow to and from the lakes, how much rain falls directly on a lake and how much water evaporates. Many lakes are regulated, so the water levels are affected by the rules governing water management. Regarding regulation of the largest power-producing rivers this effect is especially large.

High water levels in lakes can lead to flooding with implications for a variety of interests such as housing, agriculture, electricity and water supply. Even low water levels may have implications for water supply and irrigation, among other things.  For Mälaren and Vänern, the low water levels can affect the intense shipping traffic.

It is not possible to give a general answer on how water levels in lakes will change in future climate. Some lakes may get higher water levels, while other lakes, mostly in south-eastern Sweden, may have problems with low water levels. Seasonal variations can also change.