Improving our understanding of relative sea-level (RSL) change in near-field areas is important for testing and improving numerical models of glacial isostatic adjustment (GIA) and regional RSL change. In Norway, parts of the outer coast currently experience rising RSL where the ongoing global mean sea-level rise is greater than GIA-related land uplift. However, due to lacking pre-instrumental RSL-data over the last millennium, this transition to rising RSL is not well constrained in time and space. Here, we provide a new RSL reconstruction covering the last 500 years for the Vesterålen archipelago in northern Norway, bridging the gap between previous paleo-RSL reconstructions and the instrumental record in the region. Our Sea-Level Index Points (SLIPs) are based on comparing assemblages of preserved agglutinated foraminifera from salt marsh sediment cores with their local distribution in the modern nearshore environment. SLIP-ages are derived from an age-depth model based on 210 Pb- and 14 C-dating. Our data (including 2σ uncertainties) suggest that local RSL, which was falling throughout the Late Holocene, had reached 4 ± 24.6 cm asl (relative to msl of period 1996-2014), around 1535 (1450 – 1650) CE. RSL then continued to fall at a slower rate until around 1852 (1801 – 1896) CE, where it reached as low as 23 ± 11 cm bsl. Sediments dated by 137 Cs indicate a RSL lower than 5.7 cm bsl (97.5%, 16.5 ± 10.8 cm bsl) around 1975 (1963 - 1986) CE. From this we conclude that the change from falling to rising RSL probably occurred sometime in the period 1852 – 1975 CE.
Lilienthal et al. (Wed,) studied this question.