Sources and distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) in sediments from the east coastal sea of China: Application of GDGT-based paleothermometry to a shallow marginal sea

TEX86 paleothermometer as an indication of bottom water temperature in the Yellow Sea

“…Strong correlation of TEX H 86 in surface sediments and annual mean summer SST (R 2 0.84) has been reported from the east coastal seas of China (Lü et al, 2014), but most of samples in that study were nearshore (< 50 m) and only 12 sites were in the area of our study. Correlation between TEX H 86 and seasonal SST at those 12 sites (data from Lü et al, 2014) was stronger in autumn and winter than in summer (Fig. 7A).…”

“…7B). From this we conclude that the TEX H 86 calibration for summer SST (Lü et al, 2014) is likely applicable for shallow coastal areas of the East China Seas, but not for deeper, offshore locations. Further evidence that TEX 86 and U K 0 37 reflect different temperature signals comes from down core reconstruction for sediment core F10B from the southeast YS (water depth 79 m; Fig.…”

“…7A). Nevertheless, at the other 36 sites (data from Lü et al, 2014), TEX H 86 was more highly correlated with summer and autumn SST than with winter SST (Fig. 7B).…”

“…In the Pearl River estuary, both GDGT-2 and GDGT-3 showed no correlation with crenarchaeol and the GDGT-2/GDGT-3 ratio was significantly lower than that in the open ocean, suggesting that MG II Euryarchaeota may be another source for the GDGT pool in addition to Thaumarchaeota . On the other hand,TEX H 86 temperatures calculated with the global calibration (Kim et al, 2010) were close to or higher than mean annual SST from the Changjiang River estuary and the coastal ECS (Lü et al, 2014) where the GDGT-2/GDGT-3 ratio fluctuated around 2.8 (Lü et al, 2014, Supplementary data). Both GDGT-2 and GDGT-3 correlated highly with crenarchaeol in our study, with a range of GDGT-2/GDGT-3 (2.2-3.4) similar to the Changjiang River estuary, suggesting that variation in archaeal community may not be the major cause for the low TEX 86 -derived temperatures from the southern YS.…”

“…Up to 5 m thick sequences of Holocene mud (Yang et al, 2003) have provided several detailed records of oceanographic, ecological and climatic change in the YS since the end of the last glacial period (Kong et al, 2006;Xiang et al, 2008;Xing et al, 2012). Some studies indicated a correlation of TEX H 86 and annual mean SST (R 2 0.61) in the ECS (Zhu et al, 2011) and a better correlation with annual mean summer SST (R 2 0.84) in the east coastal seas of China (Lü et al, 2014), but we know little about the relationship between subsurface temperature and TEX 86 proxy and vertical distribution of GDGTs in the YS. We therefore report on the abundance of GDGTs and the TEX 86 index in surface sediment from 31 sites and in suspended particles from one site of the YS, with the aim of better understanding this temperature proxy so that it can be applied to reconstructing Holocene temperature changes.…”