Seasonal variability of dissolved oxygen, percent oxygen saturation, and apparent oxygen utilization in the Atlantic and Pacific Oceans

Using objectively analyzed seasonal fields of dissolved oxygen content, percent oxygen saturation, and apparent oxygen utilization (AOU), we describe the large-scale seasonal variability of oxygen for the Atlantic and Pacific Oceans in the upper 400 m. The winter minus summer basin zonal averages of AOU reveal a two-layer feature in both the Atlantic and the Pacific, for both hemispheres. Biological activity and seasonal stratification in the summer give the upper 50–75 m of the water column in each basin a lower AOU in summer than winter. Greater mixing of upper ocean waters in winter gives the 75–400 m layer lower AOU values in that season. The basin integral seasonal volumes of oxygen for both the North Atlantic and the North Pacific mirror what is occurring in the atmosphere, indicating that there is a seasonal flux of oxygen across the air–sea interface. Winter total O2 volume in the ocean is above the annual mean; the summer volume is below. Larger seasonal differences in the total O2 content are observed in the North Atlantic Ocean than the North Pacific Ocean. A seasonal net outgassing (SNO) of 8.3×1014 moles O2 is calculated from basin means, which is 25% higher than previous results.