Climate and Environmental Physics

Introduction

The climate of our planet is expected to change significantly within the next century due to the increasing greenhouse effect. Our expectations are mainly based on model calculations, but it is also possible to reconstruct the response of the global climate system to certain disturbances by investigating past global changes. Excellent archives of such changes are the polar ice sheets. The analyses of ice cores drilled in the central parts of the large ice sheets do not only allow us to reconstruct the local temperature, the annual precipitation rate or other regional environmental parameters but also the composition of the atmosphere in the past. The oldest recovered ice reaches 800'000 years back in time and was drilled between 1999 and 2004 at Dome Concordia (Antarctica, 75°06'S/123°21'E).

Analytical methods

We measure the concentrations of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as well as the isotopic composition (e.g. d13C of CO2 and d18O of O2) of the air which is enclosed in bubbles or in air hydrates in the ice. To measure the CO2 concentration an ice sample is broken into small pieces in vacuum; the extracted air is measured with Infrared Laser Spectroscopy. For the CH4 and N2O measurements we are melting the ice samples in an evacuated glass container; CH4 and N2O is detected with a Gaschromatograph. For the isotopic analysis the ice is ground in vacuum with a milling cutter; analysis is performed with Mass Spectrometry. With our Continuous Flow Analysis (CFA) system we are able to record continuous, highly resolved (< 1cm) concentration profiles of different tracers incorporated in the ice. This is achieved by melting the ice samples continuously and analysing the meltwater online and simultaneously for the different chemical species. At the moment the following species can be measured: H2O2, HCHO, NH4+, Ca2+, NO3-, Na+, DOC and total conductivity. Most of them are analysed by fluorescence or absorption spectrometry. These measurements are often performed in the field directly after drilling the ice cores in order to prevent contamination during transport and storage.