This dataset presents stable oxygen isotope ratios measured on the planktic foraminifer Globigerina bulloides at International Ocean Discovery Program Site U1540 (55° 8.47ʹ S, 114° 50.52ʹ W; 3,580 m) during Marine Isotope Stage 12-10. Full replicates were conducted to determine the 1σ-uncertainty of the analyses. The results are expressed in delta-notation (δ¹⁸O) with reference to the Vienna Pee Dee Belemnite (VPDB) standard. The samples were measured with a Thermo Fisher Scientific MAT 253 isotope ratio mass spectrometer coupled to a Kiel IV carbonate preparation device at the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research at Kiel University (Kiel, Germany).