The novel hydroxylated tetraether index RI-OH' as a sea surface temperature proxy for the period 160-50 ka BP off the Iberian Margin

International audienceThe stable oxygen isotope ratio (δ18O) of planktic foraminifers, the C37 ketone unsaturation ratio (UK′37) and the TetraEther indeX of tetraethers consisting of 86 carbon atoms (TEX86) are three well-known examples of paleothermometric proxies. These established proxies are in the realism phase of the Elderfield proxy curve (2002 Geochim. Cosmochim. Acta 66 Suppl. 1, 213, DOI: 10.1016/S0016-7037(02)01009-8), which means that their advantages and shortcomings are relatively well evidenced, though not fully understood. By contrast, the Ring Index of hydroxylated tetraethers (RI-OH′) is an example of novel paleothermometer. RI-OH′ is still in the optimism phase, so its potential in paleothermometry remains to be further explored.Here, we present new high-resolution temperature records over the interval 160–50 ka BP using four organic proxies (RI-OH′, RI-OH, TEX86 and UK′37) from three deep-sea sediment cores located in a north-south transect along the Iberian Margin. RI-OH′, RI-OH and TEX86 are based on LC-MS analyses of individual tetraethers with a two-column HPLC and improved mass spectrometric method. We analyzed all organic proxies in the same organic extracts to optimize proxy-proxy comparisons and phase relationship studies.Our main results strengthen the optimism concerning the novel RI-OH′ proxy for five reasons. 1/, the only existing global core-top calibration to date allows to reconstruct realistic sea surface temperature (SST) from RI-OH′ in comparison to those derived from UK′37 and TEX86. 2/, RI-OH′ allows to establish plausible latitudinal temperature gradients, which are reasonably coherent with those based on UK′37 and TEX86. 3/, RI-OH′ records resemble those from established paleothermometers, especially UK′37 and δ18O of planktic foraminifers that better reflect SST than does TEX86. 4/, RI-OH′ responds to Dansgaard-Oeschger and Heinrich events as expected for North Atlantic SST proxies, which supports a direct relationship with Greenland temperature records. 5/, the outputs of a bipolar seesaw model forced with the RI-OH′ record are well correlated with Antarctic paleotemperatures as expected from theoretical considerations.Overall, our main findings support a continued interest on the novel hydroxylated tetraether paleothermometer RI-OH′ so that it can progress along the Elderfield proxy curve. This work complements our first promising attempt based on a RI-OH record for a shallow core from the western Mediterranean Sea, located in a complex sedimentary setting much less favorable than the Iberian Margin (Davtian et al., 2019 Paleoceanography and Paleoclimatology 34, 616–634, DOI: 10.1029/2018PA003452)