Late Holocene sea-level change in Arctic Norway

• First precise late Holocene sea-level reconstruction for the Vesterålen Islands.
• First applied salt-marsh testate amoebae relative sea-level reconstruction.
• Foraminifera constrain the late Holocene sea-level trend.
• Relative sea-level fell at −0.7 to −0.9 mm yr−1 over the past 3300 years in NW Norway.
• Existing GIA models can be improved upon by using precise sea-level index points.

Relative sea-level data from the pre-industrial era are required for validating geophysical models of glacio-isostatic adjustment as well as for testing models used to make sea-level predictions based on future climate change scenarios. We present the first late Holocene (past ∼3300 years) relative sea-level reconstruction for northwestern Norway based on investigations in South Hinnøya in the Vesterålen – Lofoton archipelago. Sea-level changes are reconstructed from analyses of salt-marsh and estuarine sediments and the micro-organisms (foraminifera and testate amoebae) preserved within. The ‘indicative meaning’ of the microfauna is established from their modern distributions. Records are dated by radiocarbon, 201Pb, 137Cs and chemostratigraphical analyses. Our results show a continuous relative sea-level decline of 0.7–0.9 mm yr−1 for South Hinnøya during the late Holocene. The reconstruction extends the relative sea-level trend recorded by local tide gauge data which is only available for the past ∼25 years. Our reconstruction demonstrates that existing models of shoreline elevations and GIA overpredict sea-level positions during the late Holocene. We suggest that models might be adjusted in order to reconcile modelled and reconstructed sea-level changes and ultimately improve understanding of GIA in Fennoscandia.