The oxygen isotopic composition of benthic foraminiferal tests (δ¹⁸O_b) is one of the pre-eminent tools for correlating marine sediments and interpreting past terrestrial ice volume and deep-ocean temperatures. Despite the prevalence of δ¹⁸O_b applications to marine sediment cores over the Quaternary, its use is limited in the Arctic Ocean because of low benthic foraminiferal abundances, challenges with constructing independent sediment core age models, and an apparent muted amplitude of Arctic δ¹⁸O_b variability compared to open-ocean records. Here we evaluate the controls on Arctic δ¹⁸O_b by using ostracode  paleothermometry to generate a composite record of the δ¹⁸O of seawater (δ¹⁸O_sw) from 12 sediment cores in the intermediate to deep Arctic Ocean (700–2700 m) that covers the last 600 kyr based on biostratigraphy and orbitally tuned age models. Results show that Arctic δ¹⁸O_b was generally higher than open-ocean δ¹⁸O_b during interglacials but was generally equivalent to global reference records during glacial periods. The reduced glacial–interglacial Arctic δ¹⁸O_b range resulted in part from the opposing effect of temperature, with intermediate to deep Arctic warming during glacials counteracting the whole-ocean δ¹⁸O_sw increase from expanded terrestrial ice sheets. After removing the temperature effect from δ¹⁸O_b, we find that the intermediate to deep Arctic experienced large (≥1 ‰) variations in local δ¹⁸O_sw, with generally higher local δ¹⁸O_sw during interglacials and lower δ¹⁸O_sw during glacials. Both the magnitude and timing of low local δ¹⁸O_sw intervals are inconsistent with the recent proposal of freshwater intervals in the Arctic Ocean during past glaciations. Instead, we suggest that lower local δ¹⁸O_sw in the intermediate to deep Arctic Ocean during glaciations reflected weaker upper-ocean stratification and more efficient transport of low-δ¹⁸O_sw Arctic surface waters to depth by mixing and/or brine rejection.