Climate-driven deepwater deoxygenation is a growing global concern for lake ecosystems. We developed a simple 1-D deepwater oxygen profile model to understand the underlying physical mechanisms and to quantify the required climate-adaptive interventions. It was applied to Lake Erken, Sweden, using hydrodynamic forcing under three Representative Concentration Pathway (RCP) scenarios. From 2020 to 2099, the annual anoxic factor (the number of days when the anoxic sediment area equals the lake surface area) projections show non-significant trends under RCP2.6, while increasing by 0.4 and 0.6 days year⁻¹ decade⁻¹ under RCP6.0 and RCP8.5, respectively. This climate-driven future deoxygenation, consistent across multiple oxygen metrics, mainly stems from prolonged stratification. To mitigate climate impacts by 2100, oxygen depletion rates, as a proxy for eutrophication, would need to be reduced by approximately 9–13%, 20–24% and 26–35% under RCP2.6, RCP6.0 and RCP8.5, respectively. This data-efficient framework can be applied to physically-dominated, seasonally stratified lakes.