Dripstones tell of storm track changes
A new study in Nature Communications shows that storm tracks were located further to the south of Europe during the last ice age, 25,000 years ago.
As climate changed over the last millennia the global wind patterns progressively modified their shape. Central and southern Europe are particularly sensitive to changes in the storm track. By analysing the geochemical composition of dripstones recovered from an Alpine cave in Switzerland, Lütscher et al. were able to extract information on how meteoric precipitation (rainfall and snow) was transported from the ocean to the cave site during the last ice age, a period when large parts of the Alps were completely ice-covered.
Dating stalagmites accurately
The isotopic composition of water depends primarily on the air temperature and the transport history. Dripstones incorporate this information which may be preserved for millennia from surface erosion processes. By accurately dating stalagmites from the Last Glacial Maximum (LGM), the authors of the paper were able to quantify that substantially more water had been transported across the Alps than at present.
Associate Professor Harald Sodemann, at the University of Bergen’s (UiB) Geophysical Institute and the Bjerknes Centre for Climate Research, has developed a model-based method for detecting the evaporation sources and atmospheric transport paths of water vapour on its way to precipitation.
Supporting earlier analysis
Together with colleagues in Europe, Sodemann has performed analysis which supports earlier hypotheses that the storm track, which brings precipitating weather systems from the Atlantic ocean to continental Europe, was indeed located further to the south 25,000 years ago.
Therefore more moisture from the warm subtropics was forced over the Alps, leading to the formation of massive glacier domes south of the Alpine main crest. This work can serve as an important benchmark for simulations of storm track changes for past and possibly future climate conditions.
'North Atlantic storm track changes during the Last Glacial Maximum recorded by Alpine speleothems', by Mark Lütscher, R. Boch, H. Sodemann, C. Spötl, H. Cheng, R. L. Edwards, S. Frisia, F. Hof & W. Müller in Nature Communications 6:6344 (doi:10.1038/ncomms7344).