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Equatorial Deep Jets: an analysis of data sets at 10 W Lucia Bunge Christine Provost Annie Kartavtseff. Organization of the presentation. Introduction Data year 2000 Data year 2003 Conclusion. Where is 10° W?. Definition of Equatorial Deep Jets (EDJ). Presents in all tropical oceans.

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  1. Equatorial Deep Jets: an analysis of data sets at 10 WLucia BungeChristine ProvostAnnie Kartavtseff

  2. Organization of the presentation • Introduction • Data year 2000 • Data year 2003 • Conclusion

  3. Where is 10° W?

  4. Definition of Equatorial Deep Jets (EDJ) • Presents in all tropical oceans. • Strong zonal speeds (>10 cm/s). • Small vertical scales (400-600 m). • Found between the thermocline and 2500 m, and between 1°S and 1°N. • Zonal length??? Maybe 10 or 15°? • Time scale???

  5. LADCP profile at 23º W Vertical scale=distance between two positive or negative maxima Snapshot summer 1999

  6. Problems associated with measuring EDJs • Very long time scales? Quasi-stationary? • Small vertical scales. • Mixed up with other signals of similar or larger amplitude, e.g. annual cycle of baroclinic mode 3 or 4.

  7. Different ways of measuring velocity Currentmeter time series LADCP profile Low spatial resolution What it is important to distinguish jets are the vertical scales!!!!! No time scale

  8. 0.45˚S E 0.45˚N ADCP E1 N1 745 S1 825 840 E2 930 N2 E3 1000 1060 N3 1120 E4 1190 S2 1360 N4 E5 1385 1415 E6 1460 S3 1525 Mooring array for 2000 at 10º W 13 currentmeters between 745 and 1525 m

  9. To study the EDJs, we will focus on • Zonal velocity component • Vertical scales • Oscillations of 50-80 days and lower frequencies (it is only a these time scales that we observe vertical scales comparable to those of EDJs)

  10. 50-80 day oscillations • Present in almost all records. • Phase relations between depths that change… Is it possible to speak about EDJs of 70-day duration?

  11. The annual cycle With the aim of eliminating variability coming from larger vertical scales (e.g. annual cycle), we calculate a weighted average of all series and then subtract it from each series.

  12. Two vertical scales

  13. Evolution of “u” with and without the vertical mean

  14. Comparison with a LADCP profile made between July and August 2000, at 10º W.

  15. Summarizing the 2000 data • We find in the moorings a vertical scale of 500 m associated with a temporal scale of 8 months. These scales seem to be related to the EDJs observed at 700 and 1000 m in the LADCP data. • We also find a vertical scale of 800 m associated with a interannual variation + 50-80 day oscillations.

  16. Question-supposition • Do EDJs “feel” each other? • If they do, do they do it only in couples or is it the whole water column (where jets are present) that oscillates in a coherent manner?

  17. 775 930 1120 1265 1500 1600 1710 Nine months of new data (2003) Single mooring 7 currentmeters in ~1000 m

  18. How do the vertical means of 2000 and 2003 compare? 775-1710 m 745-1525 m

  19. Evolution of “u” with and without the vertical mean

  20. MEAN Vertical mean and residues Only the 930 and 1265 currentmeters have a noticeable negative correlation

  21. Summarizing the 2003 data • The vertical means are in good agreement. • The vertical scales observed match those of EDJs, but they are not necessarily related to the measurable time scales (no correlation between them). • In this case, EDJs timescales cannot be determined. • Comparing to data in 2000, in 2003 EDJs seem to be present during all the measuring time and at all depths.

  22. General conclusions (and questions) • EDJ may have variable time scales. Data of the array in 2000 show vertical scales comparable to those of jets associated with an ~8 month time scale, much shorter than estimated before (at least 5 years). • Results suggest an intermittent behavior. • Are EDJs events that occur by “couples”? In data of 2003, only EDJs at 930 and 1260 m are synchronized. Is the jet at 1500-1600 m a permanent eastward jet? • For both time intervals, the position of EDJs did not change… but the direction did. Is the presence of this permanent jet affecting the formation of a jet just above? • Fluctuations of 60-day period may have an important role in triggering EDJs events.

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