Quantitative climate reconstruction from late-glacial and early Holocene plant macrofossils in western Norway using the probability density function approach

Climate changes during the deglaciation are often derived from proxies such as chironomids and pollen but reconstructions are particularly difficult during cold periods. Plant macrofossils in lake sediments can be numerous during cold, treeless periods. They can often be identified to species level and therefore have the potential to be used for quantitative climate reconstructions in treeless situations such as the late-glacial in western Norway. To explore the potential of using plant macrofossils to quantify late-glacial climate change we prepared a modern data-set by digitizing 600 arctic circumpolar species distributions. We combined them with gridded climate data to determine their species-climate envelopes for mean January and July temperatures. As a test, we selected species that grow in arctic Fennoscandia today and applied a probabilistic indicator species approach (probability density functions - pdf) to their modern occurrence data and found that contemporary temperatures can be reconstructed within the uncertainty ranges. We applied the approach to a late-glacial and early Holocene plant macrofossil sequence from Krakenes, western Norway (5 degrees E 62 degrees 1'N) and compared it to existing reconstructions made from pollen and chironomid fossil data. The reconstructed deglacial climate based on the plant macrofossil assemblage was comparable to the other proxy reconstructions except that the mean July temperature was higher during the coldest phase. Plant macrofossils provide additional information to the other proxy reconstructions and a probabilistic approach gives robust uncertainty estimates. This is a good starting point for obtaining more knowledge on late-glacial climate change using plant macrofossils. (C) 2011 Elsevier B.V. All rights reserved.