Eddy correlation – basic principles 10 20 30 40 50 60 310 311 -5 5 O2 (µM) uz (cm s-1) Time (sec) Example of measured vertical velocity and O2 data through 1 min where eddy correlations are visible: Noise in data. Means and smoothing added. Typical pattern visible: when velocity points down (yellow) the O2 concentration is above average, and when velocity points up (green) the O2 concentration is below average. This pattern gives over time a net O2 transport down towards sediment surface. Time averaged vertical flux Source: Peter Berg

Eddy correlation – flux calculation 310 311 10 20 30 40 50 60 -5 5 O 2 ( M) uz (cm s-1) m Same data, but compressed. Same data Source: Peter Berg

Eddy correlation – flux calculation 310 311 10 20 30 40 50 60 -5 5 O 2 ( M) uz (cm s-1) m 10 20 30 40 50 60 Time (sec) Cumulative flux (mmol m-2) 0.02 0.04 0.06 0.08 0.1 Important variable: cumulative flux. Looks like this for these data. A clear linear trend indicate a good strong flux signal in data. Rule of thumb: Need ~10 min of good data to get a statistically sound flux estimate. Source: Peter Berg