Introduction
Our vision is to identify and understand relevant physical and chemical Earth system processes, their evolution over time and their impact on the Earth's climate. To do so, the Environmental Isotope group explores the diverse and complex isotope compositions of materials and molecules relevant for these processes to its best. Therefore, the goal is to measure diverse isotope compositions on samples originating from many archives such as ice cores, speleothems, tree rings, and direct atmospheric air. We develop and apply dedicated preparation and detection methods to do these analyses. The focus of our activities is concentrated on temperature reconstructions and the understanding of the interaction of the water-carbon-oxygen cycles on Earth.
Analytical methods
Our applied methods base on different principles, i.e. mass spectrometry, laser absorption spectroscopy and some component specific detections. CEP has a long tradition of measuring the water isotope composition, documented by an oxygen isotope record of precipitation in the city of Bern since 1971. Over this time period the state-of-the-art principle of choice changed from mass spectrometry that was in use until 2010 to cavity ring-down spectroscopy ever since. From 2012 onwards, we conduct continuous isotope ratio measurements on air humidity, with a heated inlet since 2015. One of our water isotope instruments allows measuring Δ17O, a secondary parameter of oxygen isotopes, similar to dExcess.
Direct atmospheric air samples taken weekly at the High Altitude Research Station Jungfraujoch and at the Puy de Dôme Station (France) are quantified for the air compositions of the main components by performing high precision analyses of element ratios (δO2/N2, δAr/N2, δCO2/N2) and isotope ratios (δ15N2, δ17O2, δ18O2, δ40Ar) by mass spectrometry. Additionally, we determine the carbon and oxygen isotope compositions on the trace gas CO2 and CH4 using a home-built, automated GC-MS system.
We continuously monitor CO2 and O2 concentrations simultaneously of background air present at Jungfraujoch and Bern by a conventional infrared laser absorption technique for CO2 and a dedicated paramagnetic cell for O2.
The exploration of paleo-archives calls for dedicated extraction and preparation lines for isotope analyses. Over the years we have develop a suite of methods, including triple C-H-O isotope analyses of cellulose samples extracted from wood samples, a fast fluid inclusion analyses method for water isotopes, an online air extraction system from ice cores with high resolution determination of δ15N2 and δ40Ar, among others.
