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, per cent 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 b oth hemispheres. Biological activity and seasonal stratification in the sum mer 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 t he 75-400 m layer lower AOU values in that season. The basin integral seaso nal volumes of oxygen for both the North Atlantic and the North Pacific mir ror what is occurring in the atmosphere, indicating that there is a seasona l flux of oxygen across the air-sea interface. Winter total O-2 volume in t he ocean is above the annual mean; the summer volume is below. Larger seaso nal differences in the total O-2 content are observed in the North Atlantic Ocean than the North Pacific Ocean. A seasonal net outgassing (SNO) of 8.3 x 10(14) moles O-2 is calculated from basin means, which is 25% higher tha n previous results. (C) 1999 Elsevier Science Ltd. All rights reserved.