Quaternary climate

Because the North Atlantic is one of the few places on earth where surface waters become dense enough to sink to the bottom of the ocean, it plays a crucial role in global climate. Changes in the rate and extend of North Atlantic deep water formation have an impact on global climate. In addition, during glacial times massive ice sheets form on the continents surrounding the North Atlantic (Scandinavia, Iceland, Greenland, and North America).

Part of my research revolves around reconstructing the long-term evolution of (millennial-scale) climate variability in the North Atlantic. In order to get material that old, I use marine sediments obtained by the International Ocean Discovery Program (IODP). Of particular interest to me is reconstructing sea surface temperatures (SSTs) in the North Atlantic. In the open ocean SSTs are mainly controlled by the major ocean currents and hence past changes in SSTs provide key-insights into how ocean currents behaved in the past (Naafs et al., 2010). To reconstruct past variations in SSTs I use a suite of organic geochemical proxies; the C37 alkenone unsaturation index (UK’37), the tetraether index of 86 carbon atoms (TEX86), and long-chain diol index (LDI).

Sediment core from the North Atlantic spanning the last deglaciation together with a schematic overview of the biomarker distribution during the glacial and interglacial.

During glacials large continental ice sheets surrounded the North Atlantic. Where these ice sheets reached the ocean, they produced icebergs that floated out to sea. Glacial sediments from the North Atlantic (> 40 °N) are therefore rich in ice-rafted-debris (IRD), little rock particles transported to the open ocean by icebergs. Another component of my research focuses on determining the exact source of IRD and hence icebergs. Using organic geochemical tracers to reconstruct the source of icebergs allows us to 1) reconstruct extent and behaviour of continental ice sheets in the past (Naafs et al., 2013), and 2) allows us to reconstruct the path of icebergs and hence ocean currents (Naafs et al., 2011).

Bunter Eisberg Antarktis
Sediment loaded iceberg in the Antarctic

The aim of this research is to better understand the natural processes and mechanisms that drive climate, ocean dynamics, and ice sheet stability. This research is done in collaboration with (among others) Rich Pancost, Jens Hefter, and Gerald Haug.