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

• Main Author: Park, Eun Mi
• Other Authors: Mollenhauer, Gesine, Pearson, Ann
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2019
• Subjects: Glycerol dialkyl glycerol tetraethers (GDGTs); TEX86; Thaumarchaeota; Temperature proxy; sinking particles; sediment trap; 550; 550 Earth sciences and geology; ddc:550; Antarctic; Southern Ocean; The Antarctic; Antarc*; Fram Strait
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1606; https://nbn-resolving.org/urn:nbn:de:gbv:46-00107414-11

TEX86 (tetraether index of tetraethers consisting of 86 carbons) 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). This proxy is a promising tool for SST reconstructions worldwide. However, it has been recognized that the composition of GDGTs can be altered by non-thermal factors, leading to variable relationships between TEX86 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. In the first part of the thesis, the results in the eastern equatorial Guinea Basin (GBN3) show that TEXH86-derived temperatures correspond to the subsurface water depth ( 50 m), where the nutricline exists, implying the favorable habit at depth of thaumarchaeotal communities. In the coastal upwelling area off Lüderitz (LZ), the results show that the TEXH86-derived temperatures resemble the satellite-derived SSTs with a delay of 26 days during the warmer season while warm-biased estimates occur during the colder season. Relatively higher TEX86 values found imply oxygen-stress. The second part of the thesis in the eastern Fram Strait (79Adegree N; FEVI16), the TEXL86 signal corresponds to water temperature at 30-80 m depth, where nitrification might occur. In the Antarctic Polar Front (50Adegree S; PF3), the TEXL86 -derived temperatures at the shallow trap display cold and warm biases relative to the SSTs with a tendency during periods of relatively low GDGT flux, which may be more dominant in the deep trap. The warm biased TEXL86 signal ( 7 AdegreeC) compared to the SST at the deep trap and in the underlying surface sediment might be due to a contribution of GDGTs derived from Euryarchaeota or a nonliner relationship of TEXL86 with SST in the Southern Ocean. The third part of the thesis focues on ...