Browsing by Author "Luostarinen, Tiia"

The Arctic regions are believed to be most strongly affected by the climate change, with the rapid loss of sea ice during the past decades and amplified polar warming showing a clear signal of recent warming. To understand the future climate change and its mechanisms, past reconstructions of the climate variability are needed. The oceanographic conditions in Kongsfjorden, NW Svalbard, are strongly related to the characteristics of the West Spitsbergen Current (WSC), which transports Atlantic Water (AW) and therefore also heat and salt into the Arctic Ocean. It has previously been shown that changes in the inflow of AW can have a major impact on the environment of the Svalbard area. This study aims to elucidate the fluctuations of AW and to reconstruct the sea surface temperatures in Kongsfjorden during the last 500 years. Marine subfossil diatom assemblages from Kongsfjorden, NW Svalbard, were used to investigate sea surface temperatures (SST) and sea ice variability in high temporal resolution. A 49 cm long marine sediment core was analyzed for diatoms and grain size at 1.0 cm intervals. Diatoms were only abundant in the top 16 cm of the core. The AMS 14C dates suggest that the diatom data represents ca. the last 500 years. The diatom-based SST reconstruction based on the North Atlantic surface sediment sample calibration data set and WAPLS transfer function method indicates temperature variation between 4.1 to 6.0 ˚C with a mean temperature of 4.8 ˚C. The qualitative sea ice reconstruction is based on the Marginal Ice Zone (MIZ) diatom assemblage, and the results are compared with factor analysis results. A cooling trend both in SST and sea ice during the Little Ice Age can be seen throughout the past 500 years with a very recent warming during the past decades. Grain size is dominated by clay and silt, but in the upper 15 cm of the core the coarser sand fraction increases to up to 40 %, indicating change in depositional conditions. The sea ice has been present in the area throughout the past 500 years, and the changes in both SST and MIZ species reflect the changes of the different water masses in the area. A gradual warming of 1.6 °C since LIA is seen, indicating a recent increase in the AW inflow that corresponds to the measured modern temperature of 5.8 ˚C.