Interactions of Arctic and Atlantic water‐masses and associated environmental changes during the last millennium, Hornsund (SW Svalbard)

The fjords of southwestern Spitsbergen (European Arctic) are a climatically sensitive area neighbouring the mixing zone of warm northward‐flowing Atlantic water‐masses and cold Arctic Water. Owing to reasonably high accumulation rates, these settings are especially suitable for providing high‐resolution sedimentary records of regional hydrological and environmental changes. A sediment core spanning the last millennium was retrieved from the outer Hornsund fjord basin, 14 C dated and analysed for sediment grain size, ice‐rafted debris (IRD), the distribution of benthic foraminifera and their oxygen and carbon stable isotope composition. The record of sub‐centennial resolution reveals three distinctive periods: the Medieval Warm Period, the Little Ice Age (∼AD 1600–1900) and 20th‐century warming. The marine record obtained is well correlated with regional high‐resolution ice‐core records as well as with atmospheric palaeotemperature reconstructions and sea‐ice data. The colder periods stay in phase with the greater influence of less saline, cold Arctic Water indicated by subtle changes in benthic foraminifera assemblages and the δ 18 O signal, which is dominated by changes in salinity. The IRD record clearly indicates that tidewater glaciers were present in SW Spitsbergen throughout the last millennium, and most actively from the late 16th century until the end of the 19th century.