Research methods

Present and future sea level changes in Norway are a combined effect of global/regional eustasy and local isostatic adjustments. This project focuses on the physical processes of the sea level response both on a global and local/regional scale. Realistic prognosis and models for the future sea level change in Norway will require high resolution data of former sea level changes from Holocene time and up to the present.

Reliable predictions of future sea level changes for any location in Norway presuppose an understanding of the physical processes that operate. Two important processes are the thermal expansion of sea water and melting of glacial ice on land. The latter are presently intensively studied by a number of international projects and we will use published results for quantification of these processes. However, relative sea level changes in Norway are also strongly dependent on glacial-isostasy, hydro-isostasy, geoidal eustasy and also by tectonic movements. Thus sea level projections have to take into account regional as well as local variations in crustal properties around the globe.

Calculated total glacial isostatic uplift after the last glaciation

Global models are needed to make this assessment because only by looking at data worldwide can the sea level rise associated with recent melting be separated from glacial isostatic adjustment in Norway. We will build global models and calibrate them against all primary sea level data to determine the changes in global sea level that have occurred over, particularly, the last 1000 years, and also to make predictions of the future.

The computations of sea level changes will be done by global models that we will further develop on the basis of those described in Cathles (1975) and regional models described in Fjeldskaar (1997) with high spatial resolution (10 km) and prescribed glacial history of every 1000 years. The uplift in Norway will be modelled in a global and local context  and carefully assess if, and if so how much sea level rise is departing from the expected GIA. There is a need to determine clearly what can be reasonably accounted for by GIA and if and where recent and future sea level changes in Norway are departing from the expected trends.

Preliminary post-glacial sea level changes in Gulf of Finland

In addressing relative sea level change in Norway, local models are needed to assess the many local ice load changes.  The local models need to be placed in the global context, however, to capture the hydro-isostasy as accurately as possible and to understand and discount the unavoidable artefacts of the local approximation to the global load redistribution that occurs when ice melts and loads the world's oceans and changes the geoid. A synthesis of available data in Norway will be utilized to find an optimal model that describes the observations with a sufficient degree of precision. The data that will be used for the model development include tide gauge, precise leveling, GPS, fjord tilt, fresh to salt changes in lakes, etc. We want to find the best-fit between the ice history and Earth viscoelastic model. This will provide a solid context for assessing also sea level changes in Norway that are departing from the expected trend. This approach may enable us to discriminate between the contributing factors and to what degree the observed sea level data along the coast are influenced by a sea level rise associated with the recent global warming.

Changes in ocean level due to possible future changes in Greenland and Antarctic ice volumes can be  superimposed on the otherwise expected RSL changes in Norway by running the global and local models into the future and by prescribing the contributions from melting glacier ice according to different scenarios. IPCC (2007) provide different scenarios of ocean water expansion, melting rates of the remaining glaciers. We will study different scenarios, and do careful modelling of the sea level effects in Norway.