Late Holocene sea-level change and storms in southwestern Norway based on new data from intertidal basins and salt marshes

Abstract

<p>Most relative sea level (RSL) curves in Norway have been solidly constructed using sea-level index points (SLIPs) from isolation basins. Many of these curves show RSL falling at a slow and steady rate to modern sea level during the late Holocene, despite a lack of SLIPs younger than ca. 2000 years. Tide gauge records from southern and western Norway indicate that RSL may have been rising since they were installed (ca. 100 years ago), while the few RSL curves with one or two SLIPs younger than 2000 years BP hint that rates of sea-level fall accelerated during this period. This study aims to close the gap between palaeo and instrumental data by generating late Holocene SLIPs from low-elevation and intertidal basins in southwestern Norway. Geochemical analyses of the sediment cores from all the studied areas thus far suggests that marine influence has been increasing in recent centuries, possibly due to rates of eustatic sea level rise overtaking residual glacioisostatic adjustment (ca. 1-2 mm/yr) from the Last Glacial Maximum. Anecdotal evidence from local residents of Egersund, with family histories and records of past storm levels going back to the 1800s, confirm this. Discrete storm layers consisting of shell fragments in one salt marsh at the back of a sheltered intertidal basin, however, may be overprinting any subtle trends in recent RSL rise. Full results of multi-proxy analyses of 8 cores from four salt marshes and protected, intertidal basins with bedrock sills will be presented from the southwestern corner of Norway.</p>