Mineral Dust Variability in Antarctic Ice for Different Climate Conditions - Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC) - page 79

1 Introduction

Polar ice cores represent a unique archive for the deposition of aeolian dust particles
in the past, as mineral dust was transported over long distances from desert regions to
the polar ice sheets (e.g., Lambert et al. 2008 ) and is less in

uenced by local atmo-
spheric conditions then other archives. While the total dust deposition is a

fl

rst order
measure of dust mobilization, hence, climate conditions in the dust source region
(Fischer et al. 2007a ), particle-size distribution is influenced by transport efficiency.
The overall goal of this study is a quantitative interpretation of Antarctic ice core
dust records from the inception to the end of interglacial periods in terms of changes
in dust mobilization and transport. Here we use ice-core dust concentration, size and
chemical composition as well as model analysis for selected time slices and combine
the two in order to assess the dust input to the Antarctic ice sheet quantitatively. This
yields information about the emissions in the dust source regions as well as about
changes in atmospheric circulation patterns responsible for dust transport to
Antarctica on time scales ranging from seasonal to stadial-to-interstadial. In this
project variability on these timescales and their causes are investigated.

2 Materials and Methods

Using the EPICA Dronning Maud Land (EDML) ice core, continuous pro les of

dust concentration and size were obtained using a Laser Particle Counter (LPD,
Klotz Company Bad Liebenzell) and evaluated to provide a full picture of dust
transport changes over the transition from the last glacial to the Holocene (T1).
Generally, the LPD uses scattering and shadowing of laser light as detection
method, which is calibrated using spherical latex particles. Thus, the analysis of
non-spherical dust particles in ice cores could be affected by shape artefacts. Here
we performed an additional calibration, where we compared the LPD results with
Coulter Counter data, which measures the size as volume directly, from the same
depth intervals and corrected for the shape. In previous studies only non sea salt
calcium (nss-Ca) was used as dust proxy in the EDML ice core (Fischer et al.
2007b ), which represents the soluble fraction of the dust. Here, we analysed par-
ticulate dust, representing the insoluble fraction of the dust. The main advantage of
the particulate dust is the possibility to obtain additionally the dust size, as an
indicator for the transport intensity.
The atmospheric general circulation model with online coupled interactive dust
scheme ECHAM5/HAM (Stier et al. 2005 ) was used to study the dust cycle for the
interglacial time slices 6 thousand years (ka) BP (before present, where present is
de ned as 1950, mid-Holocene), 126 ka BP (Eemian) and 115 ka BP (last glacial

inception). Additionally, a pre-industrial control simulation (CTRL) was performed.
The glacial time slice 21 ka BP (Last Glacial Maximum (LGM)) was simulated as
well. The model resolution was T31 (approx. 3.75 °× 3.75 ° ). Sea-surface