Climatology and annual cycle of global ocean dissolved oxygen represented by multiple observational gridded products

Ocean dissolved oxygen (O 2 ) is an essential climate variable crucial for sustaining the marine life; thus, changes of O 2 at various spatiotemporal scales should be quantified and understood. Here, we study the climatology and annual cycle of O 2 at regional to global scales using eight available gridded observational products. These datasets are generated by different groups using different primary data selection, quality control, bias correction, and interpolation methods, including statistical and machine-learning-based mapping methods. A common set of metrics was collaboratively developed by the community of the Gridded Observational Dataset Intercomparison Project-Dissolved Oxygen (GODIP-DO) to facilitate the inter-comparison. We find that global mean O 2 profiles are consistent among all products (±3 µmol kg −1 ), with the well-established decrease from high surface values to a minimum ∼ 1000 m, and subsequent increase to higher O 2 at depth, although local differences could reach ±25 µmol kg −1 (0–1000 m). The hemispheric O 2 annual cycle correlates strongly with ocean temperature changes, suggesting the key driver of temperature for the O 2 annual cycle. However, there is substantial variation in the global mean 0–100 m O 2 annual cycle, the magnitude ranges from −1 to 0.8 µmol kg −1 , with a standard deviation of the datasets of ∼ 0.3 µmol kg −1 . Average oxygen minimum zones (OMZ) volume among the products is 80.92 × 10 6 km 3 (±1.95 %) for a 60 µmol kg −1 threshold and 152.00 × 10 6 km 3 (±1.72 %) for a 90 µmol kg −1 threshold. Our results help to depict and understand the spread among the available O 2 gridded datasets.