Decadal dynamics and predictability of oxygen and subsurface tracers in the California Current System

Abstract

The oxygen of the source waters that feed the upwelling in the California Current System shows prominent multidecadal fluctuations that are not significantly correlated with the dominant modes of Pacific climate variability. By combining observations and ocean reanalysis products between 1950 and 2010, we show that decadal changes in oxygen are linked to subsurface salinity variability and primarily controlled by ocean circulation dynamics. We find that subsurface anomalies in the core of the North Pacific Current propagate the oxygen signal downstream into the coastal upwelling system following the path of the mean gyre circulation with a time scale of 10 years. These results suggest that decadal variability in the ocean subsurface is a key process for understanding, and potentially predicting, hypoxia and other biogeochemical tracers in upwelling systems. According to the current sign of the subsurface tracer anomalies in the gyre, California may experience a new period of strong decline in oxygen by 2020.