Published data were used to analyse the long-term mean sea level trends at 17 locations located in the Europe. Stations were located in Norway, Sweden, Finland, Germany, Denmark, Netherlands, France, United Kingdom, Italy and Georgia.
The data used were all from the website of PSMSL (the Permanent Service for Mean Sea Level) which maintains a huge, worldwide database of sea level data. Only raw data were used (ie as originally recorded, without any adjustments). These data are relative to the local land levels.
The span of records of the data ranged from 86 years to 168 years; the earliest record (at Maassluis) commencing in 1848. There are records for Brest since 1807 but the data prior to 1901 were inconsistent with data from other stations and were not used in this analysis.
The plots shown below are of the annual means at each of the 17 locations. On each plot a linear “best fit” trendline has been added. The “slope” of the trendline, expressed in cm / century, are included in the table above.
ANNUAL MEAN SEA LEVEL TRENDS FOR INDIVIDUAL STATIONS
Narvik (Norway) 1929-2014
Heimsjo (Norway) 1928-2014
Bergen (Norway) 1916-2014
Oslo (Norway) 1916-2014
Vaasa (Finland) 1884-2014
Helsinki (Finland) 1879-2014
Stockholm (Sweden) 1859-2015
Olands Norra Udde (Sweden) 1887-2015
Warnemunde (Germany) 1856-2014
Copenhagen (Denmark) 1889-2012
Maassluis (Netherlands) 1848-2015
North Shields (United Kingdom) 1896-2015
Newlyn (United Kingdom) 1916-2014
Brest (France) 1901-2015
Marseille (France) 1885-2015
Trieste (Italy) 1875-2015
Poti (Georgia) 1874-2015
DISCUSSION AND COMMENTS
- The annual mean sea level trend-lines for all 17 stations are remarkably linear with no indication of inceasing or decreasing trend in recent decades.
- The values of the trendline slopes (which do not allow for changes in local land levels) are less important than the changes (acceleration or decceleration) in the trendline slopes.
- There is a wide range in the slopes of the trendlines (-72.7 to +66.5 cm/century) at different locations.
- Eight of the stations, all located in Norway, Sweden or Finland, have negative long-term trends (ie the local sea level is falling relative to the land). This reflects the significant isostatic rebound effect due to deglaciation in the Scandinavian region.
- The records for Poti have an extremely high positive trendline slope (+66.5 cm / century) which probably reflects the reported subsidence of the land level at that location.
- At all the other locations (except for Copenhagen) the trendline slopes were in the narrow range of 12.5-19.0 cm / century.
This article was written by Brian Gunter of Narooma, NSW. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Bureau of Meteorology.