DESCRIPTION OF THE SEA LEVEL SCENARIOSOn average the global sea level has risen by about 10 - 20 cm during the past century, but in Finland the land is still rising following the disappearance of ice after the last glaciation. The net effect has been a fall in relative sea level. This fall has slowed in recent decades, but this is probably a regional effect in the Baltic Sea of changes in wind climate, as similar trends are not evident on Atlantic coasts. Previous projections suggest that accelerated global sea level rise may reverse the historical downward trend on the southern coast of Finland. Are these projections still valid? And how would possible future changes in atmospheric pressure or in storm intensity affect the risk of coastal inundation?
Summary tableSummary information about the methods used to derive the sea level scenarios
The FINSKEN sea level scenarios were constructed as a combination of three factors, the global mean sea level, the absolute land uplift, and the North Atlantic Oscillation (NAO) index, that can be used as a surrogate for the water balance of the Baltic Sea.
The study was based on sea level observations (4-hour intervals) from 13 Finnish tide gauges suitable for studies of long-term changes. The trend in the time-series has been investigated. The absolute land uplift rates have been calculated by combining the relative land uplift rates (based on the observed sea level) and the global mean sea level rise.
The water balance of the Baltic Sea plays an important role in determining the mean sea level. The total water volume inside the semi-enclosed sea can vary and is thus responsible for a sea level difference of approximately one meter. These water balance variations do not even out at an annual time scale, and they explain most of the year-to-year variability of annual mean sea levels. The sea level variability at the Finnish coast has been found to correlate with the North Atlantic Oscillation (NAO) index (Kahma 1999, Johansson et al. 2001), and is utilized with a linear regression for the FINSKEN scenarios.
The scenario calculation was done by applying scenarios of global mean sea level and of the NAO index to the found relationships. Estimates of the global mean sea level for the 21st century were taken from the Third Assessment Report of the IPCC (Church et al. 2001), based on the SRES emission scenarios. According to these scenarios, the global mean sea level will rise 9-88 cm from the level of 1990 up to the year 2100. Future scenarios for the NAO index were obtained from different atmosphere-ocean general circulation models (AOGCMs).
A summary of the sea level related results of FINSKEN in Finnish is available from the web page of FIMR.
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