Master Thesis Defense by Marie Cecilie Boysen

Title: The EGRIP Dustprofile: Investigating dust content of 40,000 year old Greenland ice.

One of the greatest challenges to contemporary society is global warming. Understanding future climate changes requires a detailed knowledge of its development in the past. The Greenland ice sheet offers a unique record of climate changes that occurred in the past 100 thousand years, the study of which was intensified in past years. One interesting property of the ice is the dust content that is believed to play a major role on climate change. Through Continuous Flow Analysis (CFA), this thesis measures the amount and size distribution of dust in ice drilled from the East Greenland Ice core Project (EGRIP). Measurements of particle size and amount are made with an Abakus laser counter. The resulting data covers stadials 9 to 5 of the Last Glacial Period 30-40.000 years ago, corresponding to a depth range of 1725-1925 meters. The thesis is a side product of the EGRIP gas measurement campaign at the Physics of Ice, Climate, and Earth (PICE) section of the Niels Bohr Institute (NBI) held in August til September 2022. The data processing is presented and the resulting dust profile is analysed and compared to earlier CFA records of soluble dust (Ca2+) from NGRIP, GRIP and GISP2 for the same period. The dust profile was found to have a good correlation with the Greenland stadials 5.1 to 9, with stadials having up to 8 times more dust than the interstadials. A correlation between the delta18O temperature proxy and dust measurements is observed, and it is indicated that the warming in the Dansgaard-Oeschger events appeared abrupt, whereas the cooling was gradual. The record of large fraction particles are compared to events of fires and volcanic eruptions finding only occasional matches.

Supervisors: Helle Astrid Kjær and Anders Svensson
Censor: Sebastian Bjerregaard Simonsen