Estimation of temperature – altitude gradients during the Pleistocene–Holocene transition from Swiss stalagmites

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 (δD_FI) and oxygen isotope (δ¹⁸O_FI) measurements of fluid inclusion water. In combination with NGTs, this allows us to reconstruct the past δ¹⁸O_FI – δD_FI / temperature relation. These reconstructions show that the temporal temperature sensitivity of δ¹⁸O_FI and δD_FI (Δ(δ¹⁸O_FI) / Δ(T) and Δ(δD_FI) / Δ(T)) seems to be stable over time and therefore support the use of water isotopes for temperature reconstructions in Switzerland.