Bjerknessenteret for klimaforskning er et samarbeid mellom Universitetet i Bergen, NORCE, Nansensenteret og Havforskningsinstituttet. 

Sieben Hengste
The research team discusses the effect of low temperature on the formation of speleothems during the Last Glacial Maximum (Sieben Hengste, Switzerland). Photo R. Shone

Dripstones tell of storm track changes

A new study in Nature Communications shows storm tracks located further to the south of Europe, 25.000 years ago. 

Body

As climate changed over the last millenia the global wind patterns progressively modified their shape. Central and southern Europe are particularly sensitive to changes in the storm track. By analyzing the geochemical composition of dripstones recovered from an Alpine cave in Switzerland Luetscher 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.

Moisture precipitation across the Alps
Moisture for precipitation can be transported to the cave site directly from the North or across the Alps from the South. Both transport pathways left different imprints in the stalagmite's geochemical composition. Figure modified from Lütscher et al., 2015

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, the authors were able to quantify that substantially more water had been transported across the Alps than at present.

Harald Sodemann, associate professor at UiB and the Bjerknes Centre, has developed a model-based method for detecting the evaporation sources and atmospheric transport paths of water vapour on its way to precipitation.

Together with colleagues in Europe, their analysis 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.

 

Reference:
Marc Luetscher, R. Boch, H. Sodemann, C. Spötl, H. Cheng, R.L. Edwards, S. Frisia, F. Hof & W. Müller (2015): North Atlantic storm track changes during the Last Glacial Maximum recorded by Alpine speleothems, Nature Communications, 6:6344 | DOI: 10.1038/ncomms7344