Master Thesis Defense by Niels Schøtt Hvidberg

Title: Anatomy of Abrupt Climate Change

Abstract:
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.