Master thesis defense by Steffen Kristiansen

Titel: Quantification of bipolar volcanic eruptions during the last glacial period (12-60 ka) based on Greenland and Antarctic ice cores



From historical records and measurements, it is evident that large volcanic eruptions can have an impact on the climate. Sulfate aerosols from an eruption can disperse in the atmosphere and with precipitation or dry fall-out over ice sheets, the sulfate can build up a record. Hence, sulfate concentration can be used to detected and quantify volcanic eruptions. First a thorough explanation on how volcanic aerosols are dispersed and how they impact climate will be introduced. During the last glacial (12000 b2k – 60000 b2k) several bipolar eruptions are identified. In order to validate the estimation of the sulfate levels and detection of eruptions, a replication of the methods used by Sigl et al. (2013) is presented and the methods are validated and applied on sulfate and sulfur data from three Greenland cores (GISP2, NEEM and NGRIP) and three Antarctic cores (EDC, EDML and WD). The detected eruptions and the sulfate depositions in kg/km2 are synchronized with bipolar eruptions identified by Svensson et al. (2020). Further, a comparison in terms of  the sulfate depositions and frequencies are compared with bipolar eruptions during the last 2500 years identified by Sigl et al. (2013, 2015). A comparison that reveals a glacial with a close to expected amount of eruptions, but with an elevated sulfate background level and eruptions with higher sulfate deposition. Together with eruptions with known latitudes, the sulfate depositions are further used in order to estimate latitudinal bands for the glacial bipolar eruptions showing an overweight of north hemispheric and tropical eruptions. Additionally, seven selected eruptions are investigated for possible climatic fingerprints using δ18O records from both Greenland and Antarctica with two occurring just prior to cooling events.

Participating via Zoom by using the following link:

Supervisor: Anders Svensson

Censor: Peter Aakjær