Controlling factors of the climatological annual cycle of the surface mixed layer oxygen content: A global view

The annual cycle of global dissolved oxygen content ( O 2 C ) and mean concentration in the surface mixed layer are estimated using monthly climatological fields from World Ocean Atlas 2018 (WOA18). largest seasonal variability occurs extra-tropics between 30° 70° latitude each hemisphere. A view role entrainment, air-sea flux, biological activity controlling content/concentration is determined an mass balance model. Based on relative percentage model, entrainment only a significant driver (contributing to 20-40% total changes) mid-fall early spring when deepens transfers deeper waters. Both flux show strong cycles play critical roles layer. Air-sea ingassing late fall outgassing fall. It substantial factor throughout year controls 40-60% changes most months. Biological net source (production) summer sink (consumption) winter for content. plays more important during spring/summer (40-60%) than that fall/winter (10-30%) overall change month. model estimates value (±SD) 3.06±1.61 mol m -2 yr -1 863.7±73.8 Tmol ocean community production (ANCP) 60°S 60°N latitude, which fairly good agreement with previous studies.