Large-scale variability in Salinity and Oxygen Based on Recent Repeat Hydrographic Sections

Talley, Bindoff, LeQuere, Johnson, Mecking, Swift, Sprintall, Yashayaev, Gruber, Feely

Abstract

Salinity and oxygen variations are reviewed or examined from each ocean basin, using repeat hydrographic data. Results are considered with respect to basin-wide analyses of salinity and oxygen trends (Boyer et al., 2005; Garcia et al., 2005). Upper ocean salinity changes suggest freshening in regions of fresher water (high latitudes and Pacific Ocean), and increased salinity in regions of saltier water (subtropical latitudes and Atlantic Ocean), suggesting a strengthening of the normal atmospheric water transport. These change are communicated to the ocean interior through water mass formation and subduction. Reported oxygen decreases in the high northern and southern mid-latitude thermoclines suggest a widespread slowing of thermocline ventilation (Emerson et al., 2004; Deutsch et al., 2005; Johnson and Gruber, 2006). However, the sub tropical thermoclines of all three southern hemisphere oceans show increased oxygen, suggesting a increase in circulation that could be related to recent observations of increased dynamic height and strengthened southern hemisphere westerlies. Both the salinity and subtropical oxygen changes are consistent with anthropogenic change.