On the relationship between stable isotopes and major impurity species as inferred from a two-dimensional firn sampling approach at EDML, East Antarctica

Ice cores constitute a major palaeoclimate archive by recording, among many others, the atmospheric variations of stable oxygen and hydrogen isotopic composition of water and of soluble ionic impurities. While impurities are used as proxies for, e.g., variations in sea ice, marine biological activity and volcanism, stable isotope records are the main source of information for the reconstruction of polar temperature changes.

However, such reconstruction efforts are complicated by the fact that temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Under the assumption that specific trace components are originally deposited with the precipitated snow and its isotopic composition, the retrieved impurity records should display a similar spatial and seasonal to interannual variability as the isotope records, caused by local stratigraphic noise as well as the time-variable and intermittent precipitation patterns, respectively.

In this contribution, we investigate the possible relationship between isotope and impurity data at the East Antarctic low-accumulation site EDML. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench. This enables us (1) to study the spatial (horizontal times vertical) relationship in the data, and (2) to analyse and compare the seasonal and interannual variability after removing the strong contribution of local stratigraphic noise. By this, the study improves our understanding of the depositional mechanisms that play an important role for the formation of ice-core records, and it offers to investigate the potential of using impurities to correct isotopic variability in order to improve temperature reconstructions.