Alkenone paleotemperatures and concentrations in Miocene sediments from ODP Site 884 in the subpolar North Pacific

We measured the unsaturation index (Uk'37) and concentration of C37 alkenones in sediment samples from Ocean Drilling Program (ODP) Site 884 to quantify the evolution of sea surface temperatures (SSTs) in the western subpolar North Pacific throughout the Miocene. To calculate SSTs, we applied the linear core-top calibration of Müller et al. (1998). Alkenones were measured using a gas chromatograph with a flame ionization detector, Agilent Technologies, 7890/8890 equipped with an Agilent DB-1 column (60 m length, 0.32 mm diameter, 0.10 µm film thickness). C37 alkenone concentrations were quantified using internal standards of n-hexatricontane and n-heptatriacontane and were normalized to the dry mass of sediment extracted for each sample. Alkenones in some samples were measured using high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) using a Zorbax Exclipes PAH column using the method of Liao et al. (2023). For samples measured using HPLC-MS, C37 alkenone concentrations were not quantified.