Ice magnetization in the EPICA-Dome C ice core: preliminary results

We measured the Isothermal Remanent Magnetization (IRM) and coercivity of remanence (Hcr) of fine magnetic particles included as dust in ice samples from the EPICA ice core (East Antarctica). Atmospheric aerosol contains a significant fraction of highly magnetic iron oxides whose magnetization can be measured directly on ice samples (Lanci et al., 2001). The concentration and mineralogy of the magnetic fraction in polar ice can be estimated through standard magnetic methods used in environmental magnetism; this information on a novel property of ice allows us to investigate iron oxides concentrations in atmospheric aerosol. Lanci et al. (2004) have shown that the small amount of atmospheric dust included in ice cores can acquire an IRM which can be precisely measured directly in ice samples and can be correlated with dust concentrations in the ice. If the correlation between ice magnetization and dust concentration is good, which implies uniform magnetic properties of dust, the slope of the regression line is taken as average magnetization on the dust fraction. The intercept of the regression line with the y-axis represents a background magnetization that in not correlated with dust concentration. Lanci and Kent, (2006) have found that this background magnetization is carried by nanometric-sized grains, known as superparamagnetic (SP), and it is mostly due to meteoric fallout. Magnetic measurements on ice also provide a measure of stable magnetization (e.g., Lanci and Kent, 2006) and the coercivity of remanence, which are discussed in this paper. Both of them provide information on the magnetic properties of the aerosol and may thus be a potential tracer.