Reorganized Atmospheric Circulation During the Little Ice Age Leads to Rapid Southern California Deoxygenation

The magnitude of natural oceanic dissolved oxygen (DO) variability remains poorly understood due to the short duration observational record. Here we present a high-resolution (4–9 years) reconstruction Southern California minimum zone (OMZ) through Common Era using redox-sensitive metals. Rapid OMZ intensification on multidecadal timescales reveals greater DO than observed in instrumental records. An anomalous interval intensified between 1600–1750 CE contradicts expectation better-ventilated mid-depth North Pacific during cool climates. Although influence low-DO Equatorial Intermediate Water Margin was likely weaker this interval, attribute rapid deoxygenation reduced (NPIW) ventilation. NPIW ventilation thus appears very sensitive atmospheric circulation reorganization (e.g., weakened Siberian High and Aleutian Low). In addition temperature-induced gas solubility, forcing under future anthropogenic influences could amplify variability.