Master Thesis Defense by Niels Schøtt Hvidberg

Title: Anatomy of Abrupt Climate Change

In this thesis, the Improved Ramp Fitting Method has been developed, tested, and applied to paleoclimatic records from ice cores and speleothems in order to investigate abrupt Dansgaard-Oeschger transitions during the last glacial period. The method is used to characterize the age and timing of a series of 15 Dansgaard-Oeschger events (27-60 ka BP) in records from the NorthGRIP and NEEM ice cores from Greenland, and from speleothems from the Hulu cave in Southeast China. The study investigate the phasing and anatomy of the Dansgaard-Oeschger events across different proxy records from ice cores (d18O, Ca2+, Na+, D-excess). A lead of 20 years and 10 years to d18O are found for D-excess and Ca2+ respectively. The study also compares the timing of Dansgaard-Oeschger events between ice core and speleothem records, and concludes that they happen synchronously or within a lead-lag of 10 years.

Supervisors: Sune Olander Rasmussen og Aslak Grinsted.
Censor: Per Knudsen, DTU Space.