Experimental reconstruction of temperature - altitude in the past remain often elusive. With the development of a combined vacuum crushing and sieving system (CVCS), it is now possible to determine paleotemperatures from the noble gases dissolved in minute amounts of water from inclusions in speleothems that have grown under a broad range of climatic conditions. Here we present noble gas temperature (NGT) estimates during the last deglaciation, which are based on two stalagmites from Milandre Cave (stalagmite M6) and Grotte aux Fées de Vallorbe (stalagmite GEF1), Jura Mountains, Switzerland. The caves are located at different geographical altitudes (Milandre Cave: 373 m a.s.l. and Grotte aux Fées de Vallorbe: 895 m a.s.l.) and thus allow for a reconstruction of the respective temperature – altitude gradients within Switzerland during the last deglaciation. Our reconstruction shows that the past temperature – altitude gradients are within 1σ error in agreement with the modern temperature – altitude gradient, suggesting that the local temperature – altitude gradient was rather stable over time. In addition to the noble gas analysis, we complemented our study with deuterium (δDFI) and oxygen isotope (δ18OFI) measurements of fluid inclusion water. In combination with NGTs, this allows us to reconstruct the past δ18OFI – δDFI / temperature relation. These reconstructions show that the temporal temperature sensitivity of δ18OFI and δDFI (Δ(δ18OFI) / Δ(T) and Δ(δDFI) / Δ(T)) seems to be stable over time and therefore support the use of water isotopes for temperature reconstructions in Switzerland.
Bibliographical noteFunding Information:
We would like to thank A. Süesli, D. Niederer, and U. Menet for their constant and highly appreciated support in the noble gas laboratory. Frequent discussions with all members of the Environmental Isotope group at Eawag and the members of the Stalclim project (grant no. CRSI22-132646/1) are greatly acknowledged. We also thank Prof. Dr. Christoph Spötl and another anonymous reviewer for their helpful comments on an earlier version of our work which significantly improved our study. This work was supported by the Swiss National Science Foundation (grant no. 200021_155891/1 ). We thank EAWAG for providing an additional grant for supporting Elaheh Ghadiri.
- stable isotope
- temperature – altitude gradient