Behaviour of the Baltic Sea surface based on tide gauge and GPS observations

• Main Author: Kiijärvi, Anne
• Other Authors: Vermeer, Martin, Kahma, Kimmo, Insinööritieteiden korkeakoulu, School of Engineering, Maankäyttötieteiden laitos, Aalto-yliopisto, Aalto University
• Format: Master Thesis
• Language: Finnish
• Published: 2012
• Subjects: tide gauge; sea-level rise; Baltic Sea; mareografi; merenpinnan korkeuden muutokset; Itämeri; Greenland; Fennoscandia
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/99946

There are 13 tide gauges on the coast of Finland. These tide gauges are uplifting because of the Glacial Isostatic Adjustment in Fennoscandia, which impacts to the tide gauge measurements. Over the last decades GPS-technology has been used in glacial isostatic adjustment monitoring. If post-glacial uplift is taken into account, it is possible to know the correct sea level changes at the tide gauges. This thesis studies the differences in rate of sea level rise between tide gauges on different parts of the coast of Finland, and whether these differences have changed over the last decades. These differences can be affected by climate change, which is the reason why Greenland and other land ice formations are melting. Melting of land ice has accelerated and it is affecting both sea level rise and gravity changes. The Permanent Service for Mean Sea Level tide gauge measurements from the coast of Finland and land uplift values from Lidberg's research group from 2009 were used in this work. GPS results were taken from Finland, Sweden and Estonia. Tide gauge measurements were processed with the weighted linear least squares method and land uplift measurements were interpolated to tide gauges using Delaunay-triangulation. All results were compared to Degerby's tide gauge. Relative sea level changes were obtained by the integration of tide gauge and land uplift results. By constructing relative values it was possible to remove some factors which are affecting the sea level in the Baltic Sea. In this work are also described many of the different factors, which affect the regional sea level. These weren't taken into account in the results. When all data from tide gauges were used, sea level change differs from Degerby by an amount of between -0,38 - 0,78 mm/year ± 0,50 mm/year. Temporal sea level changes between different periods can be calculated, when only temporal changes in tide gauge measurements are used. Land uplift is supposed to be constant in tide gauge data. The difference between different time series sea level ...