The Novel Hydroxylated Tetraether Index RI‐OH′ as a Sea Surface Temperature Proxy for the 160‐45 ka BP Period Off the Iberian Margin

Abstract

Sea surface temperature (SST) records from the southern Iberian Margin (Figure 1a) are typically cited as reference signals for North Atlantic climate variations (

Rapid Climate Changes in the Westernmost Mediterranean (Alboran Sea) Over the Last 35 kyr: New Insights From Four Lipid Paleothermometers (UK'37, TEXH86, RI‐OH', and LDI)

“…Although the analytical errors for these proxies are relatively small, their calibration errors are substantial, that is, 1.5°C for U K ' 37 (Müller et al., 1998), 1.0°C for TEX H 86 (Kim et al., 2015), 3.0°C for LDI (de Bar et al., 2020), and, especially, 6°C for RI‐OH' (Fietz et al., 2020). The large calibration error for RI‐OH' may be due to the so far limited core top calibration and perhaps to non‐thermal effects on the OH‐GDGTs distribution (Davtian et al., 2021). Hence, the differences in the absolute values of the proxy‐derived SST estimates for the Holocene may be statistically insignificant, as discussed earlier for the differences of U K' 37 ‐ and LDI‐derived SST estimates obtained in core 434G from the western Alboran Sea (Rodrigo‐Gámiz et al., 2014).…”

“…Furthermore, the application of a recent calibration proposed by Fietz et al. (2020) based on a modification of the ring index, as RI‐OH' (Lü et al., 2015), has been shown to generate a realistic SST reconstruction along the western Iberian Margin (Davtian et al., 2021).…”

“…Davtian et al. (2021) recently combined the U K' 37 , TEX H 86 , and RI‐OH' proxies in three deep sea sediment cores located in a north‐south transect along the Iberian Margin for the 160‐45 ka BP time period. The RI‐OH′ proxy and U K' 37 ‐derived SSTs clearly revealed the Dansgaard‐Oeschger and Heinrich events better than the TEX H 86 .…”

“…In particular, the ring index of OH-GDGTs was proposed as a tool to reconstruct summer seasonal SSTs in the Chinese coastal seas (Lü et al, 2015;Wei et al, 2020) and the Yellow Sea (Kang et al, 2017). Furthermore, the application of a recent calibration proposed by Fietz et al (2020) based on a modification of the ring index, as RI-OH' (Lü et al, 2015), has been shown to generate a realistic SST reconstruction along the western Iberian Margin (Davtian et al, 2021).…”

“…They often reveal divergences in reconstructed SSTs, which have been attributed to differences in production season or water depth of the source organisms. Davtian et al (2021) In the westernmost Mediterranean, the first biomarker SST proxy records were derived from applications of the U K' 37 index (Cacho et al, 1999(Cacho et al, , 2001(Cacho et al, , 2002Martrat et al, 2004Martrat et al, , 2014. Subsequent studies have also included the TEX H 86 index, showing comparable U K'…”