Holocene Climate Reconstructions from the Fennoscandian Tree-Line Area Based on Pollen Data from Toskaljavri

Abstract

AbstractDue to its location on the eastern North Atlantic seaboard, the Fennoscandian tree-line area is an ideal area to use biological proxies to assess the relative roles of the Scandinavian ice sheet and of oceanic, atmospheric, and astronomic forcings on regional climate history. Here we report pollen-based July mean temperature (Tjul) and annual precipitation (Pann) reconstructions from a sediment core from a high-altitude tree-line lake in northwestern Finland. The reconstructions suggest that at 9600–8300 cal yr B.P. Tjul values were low but steadily rising while Pann was high. The period of warmest summers, with Tjul values ca. 1.8°–1.6°C higher than at present, occurred at ca. 8000–6500 cal yr B.P. Since then climate has become gradually cooler. Tjul values during the “Medieval Warm Period” (ca. 1400–1000 cal yr B.P.) were ca. 0.8°C higher that at present but decreased rapidly to the low “Little Ice Age” levels at 800 cal yr B.P. We compare these results with an earlier pollen-based climate reconstruction from the same region. The reconstructions indicate a similar general Holocene Tjul pattern with lower values in the reconstruction from the high-altitude lake. However, most of the small-scale variations are not synchronous, suggesting that they may represent noise rather than signal in our data.