High-resolution microparticle profiles at NorthGRIP, Greenland: case studies of the calcium-dust relationship 

Annals of Glaciology, 35, p. 237-242, 2002 

U. Ruth
Institut für Umweltphysik, Universität Heidelberg, Im Neuenheimer Feld 299, D-69120, Germany, also at Alfred-Wegener-Institut für Polar- und Meeresforschung, Columbusstrasse, D-27568 Bremerhaven, Germany.
D. Wagenbach
Institut für Umweltphysik, Universität Heidelberg, Im Neuenheimer Feld 299, D-69120, Germany.
M. Bigler and R. Röthlisberger
Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland.
J.P. Steffensen
Geofysisk Afdeling, Niels Bohr Instituttet for Astronomi, Fysik og Geofysik, Københavns Universitet
H. Miller
Alfred-Wegener-Institut für Polar- und Meeresforschung, Columbusstrasse, D-27568 Bremerhaven, Germany.

ABSTRACT.
A novel flow-through microparticle detector was deployed concurrently with continuous flow analyses of major ions during the North Greenland Icecore Project 2000 field season. The easy-handling detector performs continuous counting and sizing. In this deployment the lower size-detection limit was conservatively set to 1.0 µm equivalent spherical particle diameter, and a depth resolution of ≤ 1 cm was achieved for microparticle concentrations. The dust concentration usually followed the Ca²⁺ variability. Here results are presented from an inspection of the Ca/dust mass ratio in 23 selected intervals, 1.65 m long each, covering different climatic periods including Holocene and Last Glacial Maximum (LGM). A (Ca²⁺/(insoluble dust) mass ratio of 0.29 was found for the Holocene and 0.11 for LGM. Changes to the Ca/dust ratio occur on an annual to multi-annual time-scale exhibiting the same pattern, i.e. lower Ca/dust ratio for higher crustal concentrations. Moreover, the Ca²⁺/dust ratio may increase significantly during episodic events such as volcanic horizons due to enhanced dissolution of CaCO₃. This calls into question the notion of deploying Ca²⁺ as a quantitative mineral dust reference species and shows the importance of variable source properties or fractionating processes during transport and deposition.