Reconstructing the Underwater Topography in the Medieval Harbour of Oslo

Many known factors are continuously affecting and changing the landscape. This can lead to challenges in interpreting archaeological remains found underwater, or in areas that used to be underwater, when their depth below the water surface at the time of deposition is unknown. This article is an attempt to investigate if it is possible to reconstruct how the underwater (submarine) landscape might have looked in Oslo in the Late Middle Ages based on data gathered in an archaeological excavation at site B8a. Calculating the known parameters that affect the underwater topography in Oslo – land uplift, sea level change, subsidence of the ground, and technical adjustment of mean sea level – resulted in a model. This model of the seabed around AD 1400 is based on up-to-date information and shows that it is possible to create a relevant framework for archaeological interpretation. Yet, there are challenges like the degree of inaccuracy of the data used, where our calculations end up with an uncertainty range of around ± 0.64 m.