Oxygen decreases and variability in the eastern equatorial Pacific
Article first published online: 17 NOV 2012
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 117, Issue C11, November 2012
How to Cite
2012), Oxygen decreases and variability in the eastern equatorial Pacific, J. Geophys. Res., 117, C11019, doi:10.1029/2012JC008043., , and (
- Issue published online: 17 NOV 2012
- Article first published online: 17 NOV 2012
- Manuscript Accepted: 3 OCT 2012
- Manuscript Revised: 2 OCT 2012
- Manuscript Received: 14 MAR 2012
- floats (oxygen);
- oxygen minimum zone
 Observations indicate increasingly large and strong oxygen minimum zones (OMZs) in the tropical Pacific over recent decades. Here we report on oxygen decreases and variability within the eastern equatorial Pacific OMZ. We construct time series from historical and profiling float oxygen data and analyze data from repeat hydrographic sections at 110°W and 85°50′W. Historical data are quite sparse for constructing oxygen time series, but floats with oxygen sensors prove to be good tools to fill measurement gaps in later parts of these time series. In the region just south of the equator a time series over the last 34 years reveals that oxygen decreases from 200 to 700 m at a rate between 0.50 and 0.83 μmol kg−1 yr−1. This strong decrease seems to be related to changes in the Pacific Decadal Oscillation (PDO). Oscillations on shorter time scales (e.g., an El Niño signal in the upper 350 m) are superimposed upon this trend. In the section data, a general trend of decreasing oxygen is present below the surface layer. While velocity differences appear related to oxygen differences in the equatorial channel, there is less correlation elsewhere. Contrasting with long-term trend computations, the trends derived from two repeat sections are obscured by the influence of seasonal and longer-term variability. Multidecadal variability (e.g., PDO) has the strongest influence on long-term trends, while El Niño, isopycnal heave, current variability, seasonal cycles, and temperature changes are less important.