Variations in GDGT flux and TEX86 thermometry in three distinct oceanic regimes of the Atlantic Ocean: a sediment trap study

• Main Author: Park, Eunmi
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Antarc*; Antarctic; Fram Strait
• Online Access: https://epic.awi.de/id/eprint/51148/; https://epic.awi.de/id/eprint/51148/1/EPark_PhDThesis_2019.pdf; https://elib.suub.uni-bremen.de/edocs/00107414-1.pdf; https://hdl.handle.net/10013/epic.8655f695-1c23-4f88-9585-7f7f17de931c

The global climate change and global warming have been observed since the pre industrial times. This phenomenon calls for immediate actions to fight climate change. The climate change of the Earth´s history is preserved in the ocean, covering ~70% of the Earth, and the understanding of this history is the significant way to predict the future climate. The temperature changes in the past ocean can be estimated using several proxies. One of the most extensively applied temperature proxy to the paleoclimate is the TEX86 (tetraether index of tetraethers consisting of 8 carbons). It is based on the relative compositions of thaumarchaeotal membrane lipids, glycerol dialkyl glycerol tetraethers (GDGTs), in marine surface sediments, allowing us to estimate sea surface temperature (SST). The ubiquities of Thaumarchaeota, one phylum of the Archaea domain, and their dominant abundance in the ocean have made them a novel proxy. However, it has been recognized that the composition of GDGTs can be altered by non thermal factors, leading the unconventional relationship between TEX8 and SST. This thesis shall contribute to a better understanding of TEX86 thermometry and the controlling environmental factors in various oceanic provinces by evaluating the GDGT flux and TEX86 related temperature estimate in sinking particles. The sinking particles collected using a time series sediment trap system can be a great value to understand the export mechanism of lipids and to estimate the seasonal variability of the proxy signal. Three different ocean regimes from the upwelling (the Guinea Basin and Lüderitz off Namibia), high latitude (the eastern Fram Strait and the Antarctic Polar Front), and the oligotrophic oceans (the central Brazil Basin) in the Atlantic Ocean are investigated. In the first part of the thesis, TEX86 values are converted to temperatures using the TEX86H calibration. The results in the eastern equatorial Guinea Basin (GBN3) show that GDGTs are mainly transported by particles containing opal. The TEX86H-derived ...