Seasonal cycles of oxygen, temperature and salinity at Ocean Weather Station P in the subarctic Pacific Ocean reveal a regular 4--6% supersaturation of oxygen in the surface waters during the summers of the 10-year period 1969--1978. The main processes causing supersaturation are surface water heating and the net effect of primary production and community respiration. The biological and heating signals are separated using a mixed layer model and estimates for the air-water gas exchange rate calculated from empirical correlations to wind speed. Biological new production during the summer (mid-May to mid-August) is estimated to be 100-300 mg C m-2 d-1. These values are within the range of independent estimates calculated from the summer nitrate depletion. There is a factor of 3 variation in the new production estimates during the period 1969-1978 with a minimum in 1973-1975. This trend is positively correlated with the interannual variation in zooplankton standing stock at station P. ¿American Geophysical Union 1987