Forced, Unforced, and Mesoscale Variability of Oceanic O2
Oxygen (O2) is critical to life at sea. Its distribution in the ocean’s interior reflects a subtle balance between physical (e.g. air-sea flux and transport) and biogeochemical (e.g. consumption at depth) processes. As the ocean warms further, its dissolved oxygen ([O2]) content is expected to decline as gas solubility decreases and ventilation weakens. Observations indicate indeed widespread [O2] losses in recent decades, with a pronounced decline in the tropical Pacific. Climate models, however, fail to reproduce the spatial patterns and magnitude of this decline. This model-observation discrepancy may be conveniently attributed to poor model representation of tropical circulation and biogeochemical processes. However, observed [O2] trends in the tropical Pacific are based on sparse data, and the role of natural variability in driving these trends remains poorly understood. In this talk, we will explore drivers of oceanic O2 variability, focusing on unforced (ENSO), forced (volcanoes), and mesoscale (tropical instability vortices) variability as simulated by the Community Earth System Model. Understanding these drivers of oceanic O2 variability is critical to the attribution of observed trends and informing monitoring networks, and presents unique insights on ocean physical and biogeochemical dynamics in a warming climate.