The small peatbog of Hässeldala in southern Sweden is located in the middle of a mixed forest, fringed with blueberry shrubs and boulders, and almost impossible to find. I stumbled upon the site more than ten years ago and was surprised to find a beautiful lake sediment sequence below the peat. About one meter of sediment contained a story of how climate and environment changed at the end of the last ice age.
One of the first to work with the Hässeldala sequence was Siwan Davies, who is now professor at Swansea University. Siwan discovered several ash layers and could show that ash from volcanic eruptions on Icelandic had reached as far as southern Sweden multiple times between 14000 and 10000 years ago. This discovery and the subsequent pollenstratigraphic work by Mamite Anderson propelled Hässeldala into fame.
Today the site and its sediment sequence is one of the most investigated in southern Sweden! Hässeldala has become an excellent example for the application of an array of different physical, geochemical and biological tools to study and refine our knowledge on the environmental impact of dramatic shifts in climate. The geochemical record (studied by Malin Kylander and published a few years ago), the diatom stratigraphy (studied by Linda Ampel; publication in press) and the investigation of midges and beetles (Jenny Watson, Nicola Whitehouse) all contribute to a better understanding of how climate shifts led to changes in the surroundings of the former lake and in the lake itself.
However, the story does not end here. New cores, a new age model (done by Maarten Blaauw) and fossil leaves extracted from Hässeldala’s sediments provide detailed information on past atmospheric carbon dioxide levels (study by Margret Steinthorsdottir, published recently). And, biomarker analysis (in progress) will help to better understand past atmospheric moisture patterns (PhD by Francesco Muschitiello). A new pollenstratigraphic study is in progress (MSc work by Artemis Charalampopulou) to refine how fast the vegetation around the former lake reacted to warming and cooling.
The different analyses of Hässeldala’s sedimentary record have resulted in a number of publications already. However, it would be great to combine all the available data sets into one single story, a story that will tell us how fast climate changed in the past, how large these changes were and how the sequence of events unfolded. Keep fingers crossed that someone finds the time to write the final story of Hässeldala!