Holocene climate variability in the Norwegian current and North Cape current inferred from benthic stable isotope records

Abstract

The Malangenfjord, with its deep sill and good hydrological communication with the Norwegian Sea, has been the site for a high resolution paleoclimatic investigation. By using benthic foraminifera and stable isotopes from a marine sediment core, this study will reconstruct the changes in inflow of warm Atlantic Water at a high-latitude setting.<br><br> Radiocarbon dating has give ages between 8000 – 1500 cal. yrs BP. The benthic δ18O values increases from 1.8‰ to 3‰ in the period from 8 to 1.5 cal. kyr yr BP. Interpretations indicate that this isotopic enrichment reflects a drop in the bottom water temperature from 10°C to 5.5°C, the latter being around 1.5°C colder than the modern temperature in the Malangenfjord. Additional data was retrieved from Ingøydjupet in the southern Barents Sea, in order to investigate the paleoclimatic changes in the North Cape Current. This record ranging from 15000 – 0 cal. yrs BP, has to tolerate a low resolution and a highly uncertain age model compared to the record from the Malangenfjord. Nevertheless it displays a deglacial unstable period, thermal optimum and a later enrichment in the benthic δ18O values from 2.8‰ to 3.6‰. The preliminary interpretation suggests a late Holocene cooling with bottom water temperatures dropping from 6°C to 2.5°C, the latter being 1.5°C colder than modern temperature for the area. The study gives evidence for a long-term cooling with rapid changes superimposed on the general trend. The overall cooling trend correlates with the decreasing insolation at 70°N and isotopic data from the North GRIP ice core project. Several cold events could be interpreted as periods with reduced inflow of Atlantic Water, and vice versa for warmer events.