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.
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.