Deep ice and mineral dust: the case of the TALDICE ice core

Mineral dust archived in polar ice cores can be used to document past atmospheric circulation variability and past climate conditions over the dust source areas. Thanks to its relative immobility and stability, eolian dust concentration has been used to synchronize deep ice cores as well as ice stratigraphies and marine sediment records. However, mineral impurities in deep ice can be affected by post-depositional physical and chemical alterations, deriving from small-scale relocation of dust grains and subsequent alteration in acidic micro-environments.

By applying a set of different techniques spanning from dust concentration and grain size to iron mineralogy and elemental composition, here we provide evidence of in situ dust physical and chemical alterations observed below 1000 m depth in the 1620-m deep TALDICE ice core drilled at Talos Dome (peripheral East Antarctica, 72°49’S, 159°11’E; 2315 m a.s.l.). Results highlight significant dust aggregation and alteration of Fe-minerals with englacial precipitation of neo-formed jarosite, occurring in parallel with the decline of ferrous minerals and depletion of some major elements. Therefore, below 1000 m depth the TALDICE dust record can be considered partly affected by acidic-oxidative weathering resulting from the interaction of dust particles with highly saline acidic brines. Although limited to only one specific site, this study opens new issues concerning the interpretation of climate signals in the deepest part of ice cores.