Time series of stable water isotope values of ice cores from Northern Greenland (Graphic: Stefanie Weißbach, Alfred-Wegener-Institut)

Human activities have serious impacts on the global environmental system and will, amongst others, significantly contribute to a change of the earth’s climate. To reliably predict the climate change of the earth and actually differentiate between natural and manmade accounts, the knowledge of the climate of the past and the forcing mechanisms of natural climate variability is essential.

Polar ice sheets of the Arctic and Antarctica are unique climate archives, preserving the climate of the past in high temporal resolution back to 800 000 years and possibly beyond. Ice core analysis gives access to a wide range of atmospheric parameters which are essential for the reconstruction of paleoclimate, such as temperature, precipitation, as well as trace compounds relevant for climate forcing like greenhouse gases and aerosols. 

One of the main fields of research of the AWI glaciology department concerns the reconstruction of paleotemperature, snow accumulation (precipitation) and the concentration of atmospheric aerosols as well as their temporal and spatial variability on the Greenland and Antarctic ice sheets.

The stable water isotopes (18O and D) in precipitation are the basis for the reconstruction of paleotemperature due to the empirical linear relationship between mean annual air temperature and the mean isotopic composition of the deposited snow. 

Investigations of annual snow accumulation provide information about changes in precipitation rates in the past and their correlation with changes in the atmospheric circulation pattern. Furthermore, the accumulation data will be used as one of the essential input data for calculating the surface mass balance of the ice sheets.

Polar firn and ice, particularly from Antarctica, represents more or less frozen ultra-pure water. Nevertheless, the tiny signals of trace impurities in polar ices, which are typically in the parts per billion down to parts per trillion range, provide information about climate and composition of the atmosphere in the past. Thus, the chemical parameters stored in solid precipitation and accumulated on polar ice sheets provide a unique key to assess the composition and natural variability of the paleo-atmosphere.