Master thesis defense by Margaret Harlan

Title: Continuous flow analysis of the Dye 3 ice core: New data from old ice

Abstract: The Dye 3 ice core was drilled to bedrock in Southern Greenland (65à11’N, 43à50’W) in 1979-1981. The southern Greenland location is characterized by relatively warm temperatures and high accumulation rates. Since its drilling, numerous analyses of the core have been performed, and the ice has since been in freezer storage both in the USA and in Denmark. In October and November 2019, remaining Dye 3 ice, was melted during a continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) section of the Niels Bohr Institute at the University of Copenhagen.

The resulting data covers approximate depths of 1753 to 1820 meters and 1865 to 1918 meters, representing the early Holocene and Glacial Transition and a section of the Last Glacial Period (Greenland Stadials 5-12) respectively. The measured data consist of records of the chemistry and impurities contained in the ice. The chemistry measurements considered in this project include NH+4 , Ca2+, and pH. Calcium and Ammonium provide information about continental dust and forest fires, respectively, and acidity aids in the identification of volcanic events contained in the core. Additionally, an Abakus laser particle counter was used to determine the quantity and grain size distribution of insoluble particles.

A high-resolution CFA record of the chemistry and impurity measurements of the Dye3 ice core is presented, with a particular focus on the concentration and size distribution of dust and other insoluble particles. The new Dye 3 record is also compared with previous measurements of Dye 3 (Steffensen, 1995), as well as CFA records from the NEEM and NGRIP ice cores (Ruth et al., 2003; Bigler, 2004; Schüpbach et al., 2018). Possible techniques making use of the particle size distribution in investigating volcanic and tephra layers in the ice are presented.

Assoc. Prof. Anders Svensson and Helle Kjær

Peter Aakjær