North Atlantic climate variability through the last glacial cycle

Abstract

This master thesis is based on recently obtained deep sea cores obtained during the NICO cruise in spring of 2018 in the Northern Atlantic Ocean. Two cores were prepared and analysed using general lightness and XRF data. Comparing this data to IODP-U1308, which had a previous age model constructed by Hodell et al. (2008) allowed us to construct our own age model for the NICO cores. Based on this age model, two main topics were investigated: the occurrence and characteristics of Heinrich events in the Northern Atlantic and temperature reconstruction using the clumped isotope proxy. Using XRF, it was found that Heinrich events 3 and 6 differed substantially from the other four Heinrich events, no apparent increase in Ca/Sr and a smaller reduction in Br counts, which is used as an indicator for organic content. Furthermore, the onset of MIS-4 marked the point where ice rafting events at this location changed from precession forcing to timescales in line with Dansgaard-Oeschger cycling. Reduction in precession power and intensifying glacial conditions are the main cause for this change. Besides this, clumped isotopic measurements were conducted on planktonic and benthic foraminifera from the modern and LGM core samples. The modern sample had a diverse assemblage whereas the glacial sample was dominated by N. pachyderma (s). Different temperature reconstruction for each species mainly created plausible results, with species with a low number of aliquots being less reliable. Deviations in temperatures signals within each period were caused by differences in growing seasons and position of the water column.