Sedimentary response of Arctic coastal wetlands to sea level rise

Arctic coastal wetlands are of international importance, providing a range of ecosystem services. They differ markedly from Atlantic saltmarshes in the limited development of the creek network, associated plant species, and the influence of the rapid influx of sediment during the spring thaw. This study presents the findings of research conducted in five Arctic coastal wetlands in northern Norway utilising ²¹⁰Pb and ¹³⁷Cs radionuclide dating techniques to investigate the recent sedimentary responses of these wetlands to alterations in sea level rise. Historically, coastal wetland evolution has been driven by glacio-isostatic adjustment (GIA) with rates between 0.5 and 1 mm/yr, similar to sites in Scotland and the northern and eastern Baltic resulting in wetland progradation. Dating of the sedimentary horizons suggests broad agreement between sediment accretion rates derived from both the ²¹⁰Pb methods and ¹³⁷Cs impulse dating methods with average rates of sediment accretion being between 0.3 and 1.9 mm/yr (dependent on site and zonation). Sea level rise in the region is between 2.2 and 2.8 mm/yr accounting for GIA, meaning that at present, sea level rise appears to be outpacing sediment accretion, resulting in negative elevation capital. The results of this study indicate that recent increases in sea level as a result of climate change are likely to have reversed the historical trend of progradation driven by isostatic uplift coupled with sediment accretion, suggesting that there may be losses of Arctic coastal wetland extent and associated ecosystem services in some areas.