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1950-1980 map

Oregon near-bottom dissolved oxygen

J. A. Barth and S. D. Pierce
College of Oceanic & Atmospheric Sciences


The National Ocean Data Center's World Ocean Database 2009 was searched for dissolved oxygen data out to the 200 m isobath. The WOD09 database was updated with additional NODC acquisitions up to April 2011. The data were required to pass all nine NODC quality control tests.

Here we map late-upwelling-season (July-Sept.) near-bottom (within 10 m or 15% of bottom depth) data ranging from 1950 to 1980, showing gridded results (color image) and raw data (points).

We use a two-stage gridding procedure. The first stage grids oxygen data in depth-latitude space, using a Barnes objective analysis (Barnes, 1994). The second stage translates from depth-latitude to a longitude-latitude grid using another Barnes analysis. The first stage uses a 4-iteration Barnes with radii of 50 m and 50 km, and the second stage uses 2 interations with radii of 8 km and 8 km. The effect of this mapping method is to allow bathymetry to influence the mapped field somewhat, reducing unrealistic smearing between deeper and shallower regions (as recommended for example by Dunn and Ridgway [2002], although methods differ).

Final results on a 1-km grid are in an ascii file available here with the three columns: longitude, latitude, and dissolved oxygen (ml/l). Oxygen column has "NaN" for missing data.



REFERENCES

Barnes, S. L. (1994) Applications of the Barnes objective analysis scheme. Part I: effects of undersampling, wave position, and station randomness. J. of Atmos. and Oceanic Tech., 11, 1433-1448.

Dunn, J. R., and K. R. Ridgway (2002) Mapping ocean properties in regions of complex topography. Deep-Sea Res. I, 49, 591-604.