Abstract Oxygen (O 2 ), a fundamental constituent of Earth's atmosphere, sustains aerobic life and maintains the equilibrium of global biogeochemical cycles. However, rapid urbanization is increasingly perturbing the natural O 2 balance, yet the distinct mechanisms driving these perturbations remain poorly understood. Here, we report the first simultaneous, high‐precision in situ O 2 observations at two contrasting sites: an industrial urban valley (Lanzhou) and a remote high‐altitude background site (Qomolangma Station). By disentangling meteorological confounders, we reveal a fundamental divergence in the controls on atmospheric O 2 variability: the remote baseline is primarily controlled by meteorological variability, especially temperature‐pressure coupling, whereas urban O 2 variability in the valley reflects the interaction between local anthropogenic emissions and large‐scale weather patterns that regulate atmospheric stability and dispersion. Crucially, mechanistic analyses of urban atmospheric oxygen depletion reveal a regime‐dependent transition in its dominant controls: (a) Aerosol pollution is marked by “physical decoupling”, where external transport disrupts the linearity between local combustion and oxygen deficits; (b) Ozone pollution, conversely, exhibits “chemical synergy”, driven by temperature‐enhanced precursor oxidation and associated secondary transformations. These findings establish urban O 2 variability as an integrator of anthropogenic emissions and atmospheric oxidation capacity, underscoring the necessity of incorporating chemical‐meteorological feedbacks into assessments of urban ecosystem sustainability and carbon budgets.
Wang et al. (Fri,) studied this question.