Isotope in Holocene precipitation from the Atlantic to Siberia: the speleothem record

Minute amounts of drip water are trapped as fluid inclusions in calcite crystals during growth of stalagmites in caves. This water represents samples of paleoprecipitation, contemporaneous with speleothem growth. This project aims at measuring the isotopic composition of this paleowater trapped in the course of the Holocene (the last 11,700 yrs). The data will be acquired from cave sites located along a 8,500 km-long longitudinal transect, following the direction of the moisture transport from Atlantic seaboard of the Europe inland to eastern Siberia (Lake Baikal). This transect will be the first to provide time-resolved data on the evolution of isotopes in the precipitation, as moisture was transported from the Atlantic Ocean deep into the largest continental mass on Earth. If successful, this project will be a major step toward using stable water isotopes in this part of the world for quantitative paleoclimate and paleohydrological studies. The applicant`s group operates one of the very few analytical lines worldwide capable of measuring the isotopic composition of fluid-inclusion water.

Minute amounts of drip water are trapped in small cavities (called fluid inclusions) when stalagmites grow in karst caves. Using one of the very few analytical lines worldwide capable of measuring the stable isotopic composition of fluid-inclusion water available at Innsbruck University, this water was retrieved and analyzed to determine the isotopic composition of meteoric precipitation contemporaneous with stalagmite growth. Within this project we collected 88 stalagmite samples from 33 caves located along a 8,500 km-long longitudinal transect extending from Atlantic coast of the Europe to eastern Siberia (Lake Baikal), following the direction of the moisture transport from the Atlantic Ocean deep into the largest continental mass on Earth. Stalagmites were precisely dated using the U-Th method to determine the time of their growth. Fluid inclusions were then analyzed from Holocene stalagmites. The data were used to reconstruct isotopic characteristics of precipitation over Northern Eurasia during the last 11,700 yrs. Fluid inclusions were found to faithfully record the isotopic compositions of ancient precipitation. Precipitation becomes isotopically lighter as moisture travels from the Atlantic coast eastward reaching minimum values in the vicinity of Lake Baikal. It also varies in north-south direction showing the most depleted values in stalagmites from Northern Ural caves. This method, therefore, can further be used to reconstruct the isotopic composition of rainfall in more distant past, during climates that are substantially different from todays one.