Particle shape accounts for instrumental discrepancy in ice core dust size distributions
- 1Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
- 2Department of Physics, University of Milan and National Institute for Nuclear Physics (INFN), Via Celoria 16, I20133 Milan, Italy
- 3Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
- 4Department of Earth and Environmental Sciences, University Milano-Bicocca, Piazza della Scienza 1, I20126 Milan, Italy
Abstract. The Klotz Abakus laser sensor and the Coulter counter are both used for measuring the size distribution of insoluble mineral dust particles in ice cores. While the Coulter counter measures particle volume accurately, the equivalent Abakus instrument measurement deviates substantially from the Coulter counter. We show that the difference between the Abakus and the Coulter counter measurements is mainly caused by the irregular shape of dust particles in ice core samples. The irregular shape means that a new calibration routine based on standard spheres is necessary for obtaining fully comparable data. This new calibration routine gives an increased accuracy to Abakus measurements, which may improve future ice core record intercomparisons. We derived an analytical model for extracting the aspect ratio of dust particles from the difference between Abakus and Coulter counter data. For verification, we measured the aspect ratio of the same samples directly using a single-particle extinction and scattering instrument. The results demonstrate that the model is accurate enough to discern between samples of aspect ratio 0.3 and 0.4 using only the comparison of Abakus and Coulter counter data.