Temperature reconstructions for the Eastern Indian Ocean based on organic-geochemical proxies (UK' 37 and TEX86)

• Main Author: Chen, Wenwen
• Other Authors: Mollenhauer, Gesine, Pälike, Heiko
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2016
• Subjects: UK'37; TEX86; upwelling; sea surface temperature; eastern Indian Ocean; 500; 500 Science; ddc:500; Indian; Sunda; Ice Sheet
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1012; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105102-19

Sea surface temperature (SST) is very important for studies of the Earth s climate system owing to the linkages between SST and various climatic processes. A reliable estimation of past SSTs is one of the main goals for paleoclimatologists to improve our understanding of oceanic and atmospheric dynamics and their connection to the global climate. Furthermore, the tropical SSTs play a key role for rapid climatic changes, because large amounts of heat and water vapor were transported from the tropics to the high latitudes. Warm SSTs at low latitude result in more evaporation and could thus induce increased ice sheet size and decreased temperatures at northern high latitudes. Establishing SST evolution in the tropics is crucial for understanding the mechanisms behind abrupt climate changes in the past. In this thesis, the main objectives are to evaluate the applicability of the UK 37 (alkenone unsaturation index) and TEXH86 (tretraether index of glycerol dialkyl glycerol tetraether with 86 carbon atoms) in the tropical Indian Ocean as well as to investigate their control mechanisms for reconstructing temperatures in the past. All studies presented herein are based on 36 surface sediments, a sediment trap covering an annual cycle and a gravity core in the eastern Indian Ocean. To assess the applicability, surface sediment samples from the Indonesian continental margin off west Sumatra, south of Java, and off the Lesser Sunda Islands are measured. In the non-upwelling regions, the results show that the UK 37 temperature estimates are up to 2 °C lower than World Ocean Atlas 2009 (WOA09) during the entire year, likely due to the reduced sensitivity of the UK 37 proxy beyond 28 °C. However, the temperatures based on TEXH86 are consistent with mean annual temperatures from the WOA09. In the upwelling areas, the UK 37-based temperature estimates reflect the SST during the upwelling season, whereas the TEXH86-based temperature estimates are up to 2 °C lower than UK 37-based temperature estimates suggesting GDGT export from ...