O concentrations in the ocean have decreased since the 1980s. Part of this decrease is due to increased ocean heat content (OHC) from global warming decreasing O solubility. As solubility in surface oceans decreases, O out gasses to the atmosphere.  Increased AOU is likely also contributing to declining ocean O concentrations. Changes in AOU in the ocean could be caused by multiple forcings, such as changes in subduction rates, changes in water mass boundaries, initial O from water mass formation, biochemical consumption of O, or changes in eddy mixing. Based on observations, global AOU increase seems to be linked to increasing OHC.