We measured the concentrations of glycerol dialkyl glycerol tetraethers (GDGTs) in sediment samples from Ocean Drilling Program (ODP) Site 118-1165. From these concentrations, we calculated the the tetraether index of tetraethers consisting of 86 carbon atoms (TEX86) to quantify the evolution of sea surface temperatures in the polar Southern Ocean during the Miocene. To calculate temperatures, we applied the core-top calibration Kim et al. (2010) for TEX86L. GDGTs were measured using high performance liquid chromatography coupled with atmospheric pressure chemical ionization using two silica columns (Acquity UPLC BEH HILIC 1.7 µm, 2.1 by 150 mm) run in series with the mobile phases of Hopmans et al. (2016). Peaks were integrated in selective ion monitoring chromatograms at m/z 1302, 1300, 1298, 1296, 1292, 1050, 1048, 1046, 1036, 1034, 1032, 1022, 1020, 1018, and 744. GDGT concentrations were quantified using an internal standard of C46 diol (m/z 744) and were normalized to the dry mass of sediment extracted for each sample. For TEX86L, SSTs were only calculated for samples with quality control indices (BIT, methane index, ring index, and GDGT 2/3) within ideal ranges.