Wind-driven variability of dissolved oxygen below the mixed layer at Station P

Variability of dissolved oxygen below the mixed layer is examined in data from Ocean Weather Station P (145°W, 50°N) in the eastern subarctic Pacific. At depths of 150 to 400 m, O2 variability on isopycnals and heaving of the climatological oxycline both contribute importantly to variability on interannual to decadal time scales. O2 anomalies adjusted for isopycnal variations are shown to be well correlated with results from a stochastic climate model driven by local Ekman pumping over the 54 year period, 1956–2010. This variability is associated with vertical heaving of isopycnals at low frequencies occurring as an integrated response to local wind‐forcing. Long‐term oxygen declines observed below the mixed layer at Station P are due to secular trends on isopycnal surfaces. These declines have been moderated over the 200–400 m depth range by the downward vertical displacement of the oxycline associated with the long‐term deepening of isopycnal surfaces. Key Points Low‐frequency variability of dissolved oxygen below the mixed layer at Station P Vertical heaving is important to variability and secular trends in oxygen Local Ekman pumping drives oxygen variability below the mixed layer