Comparison of U37K', TEX86H and LDI temperature proxies for reconstruction of south-east Australian ocean temperatures

Multiple organic proxies are used to reconstruct sea surface temperature (SST) but are rarely applied in concert. Furthermore, they have not been extensively calibrated for the Southern Hemisphere, particularly Australian waters. In an attempt to remedy this gap, we have used three organic temperature proxies: the alkenone unsaturation index (U37K'), the tetraether index from tetraethers consisting of 86 carbons (TEX₈₆) and the novel long chain diol index (LDI) to reconstruct SST using seafloor sediments from the sediment/water interface from near the Australian southern and eastern coasts. The proxies revealed temperature offsets compared with World Ocean Atlas 2009 temperature values that are attributed to differences in seasonal biomarker flux and depth habitat of the source organisms. In the southeast Australian region, U37K' and LDI provided better estimates of winter temperature at the surface than of any other season but overall were a robust measure of mean annual SST. TEX86H was consistent with previous data from other oceans; it estimated annual temperature best within the 75-100m water column. Comparison of the Australian results with the published global data sets confirm that TEX86H closely matched the correlation for annual temperature in the integrated 0-200m water depth profiles, whereas the other 2 proxies U37K' and LDI showed different correlations. The results indicate that the combined application of the three independent biomarker proxies may provide useful surface and subsurface temperature information in the Australian region.