Geomorphology of Viking and medieval harbours in the North Atlantic

• Main Author: Preston, John Ian
• Other Authors: Dugmore, Andrew, Newton, Anthony, Mudd, Simon, other
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2018
• Subjects: coastal; archaeology; Norse; medieval; sediment transport; sea level change; adaptation; Shetland; Iceland; Greenland; Garðar; Lunda; North Atlantic
• Online Access: http://hdl.handle.net/1842/31430

The aim of this thesis is to understand the role of geomorphological change in the abandonment of Norse harbours in the North Atlantic. Nodes of maritime activities that were established by Norse settlers during the Scandinavian Viking Age often developed into important towns and cities. Some of these, however, disappeared for unknown reasons. Norse harbours in the North Atlantic varied in scale. They ranged from small landing beaches used by small boats for local use through to much larger anchorages handling considerable trade and being important nodes on the transatlantic trading network. Changes in coastal geomorphology necessitated a response from seafarers. In this thesis, a conceptual framework for the formation, recovery and stability of headland-dominated sandy beaches in high-energy environments is established, based on empirical observation and on the use of the MIKE21 numerical sediment transport model. Under persistent calm climatic conditions, nearshore seabed gradient is a weak control on beach formation and persistence in embayments. However, under persistent stormy conditions, nearshore sea bed gradient becomes the prominent control. Embayments with nearshore gradients of > 0.025 m/m inhibit beach recovery on a sub-annual timescale, while gradients < 0.025 m/m promote beach recovery. These ideas are assessed in the Shetland Islands, using numerical modelling, geomorphology and OSL dating on sand blow deposits. In the late Norse era beach landing sites in Unst became prone to depletion and destruction because of increased storminess. Numerical modelling (MIKE21) supports the idea that the recovery time of different sandy beaches on Unst is dependent on average nearshore slope. The beach at Sandwick has shallow nearshore gradients and recovers quickly in the face of storminess, but beach stability at Lunda Wick is more uncertain, and thus Lunda Wick represents a more problematic landing place. The Norse harbour of The Bishop’s seat at Garðar in the Eastern Settlement of Greenland is assessed ...