Argo Floats Technical Workshop Summary in La Jolla

1. Argo Technologies Argo TC Inputs by S. Riser (UW) DBCP #22, Technical Workshop La Jolla, California

2. Argo Fleet • 2576 Active Floats

3. Argo Floats • A fleet of US, French, German and Japanese profiling floats Remark: IFREMER & JAMSTEC work on a new float generation

4. Argo Floats NEMO Provor SOLO APEX

5. Argo Cycle • Standard mission 150-200 cycles, t = 10 days,profile to 2000 m, Sensors: T, S, p sampling ~100 levels

6. Float Lifetime • Float lifetime improving but not yet optimal • Solutions: • Alkaline to Lithium batteries • Park & profile • New float generation

7. Argo Sensors Most of floats use a SeaBird CTD. About 200 floats (WHOI) use a FSI CTD T accurate to 0.005 C p accurate to 5 dbar S accurate to 0.01 Psu The SBE CTD unit pumps seawater through a fluid circuit; temperature and conductivity are measured inside this loop, pressure is measured outside. A biocide prevents fouling (growth) inside the loop.

8. Argo Profile [data from 71 levels]

9. CTD stability UW float 063 was recovered after 3 years and recalibrated. The results showed that salinity, temperature, and pressure had all remained stable to within the manufacturer’s specifications.

10. Iridium Floats • About 25 iridium floats are operating (UW) High resolution T and S data (p = 2 dbar) over a 2000 m profile sampling 1000 levels surface time  6 minutes

11. Iridium Floats • High resolution profile (75 to 1000 levels) • More bandwidth (required for other sensors) • A few min at surface vs. ~10 hours • Downlink available to e.g. upload new conf. • Collection of T and p data at drift depth • Data management ? • modem/modem, SBD, RUDICS • Cost ? (per byte << Argos, per profile ~= Argos) • Energy budget ?

12. New sensors SST There are plans to modify the CTD sensor on floats in order to measure SST; this will be done by adding a 2nd thermistor outside of the CTD tube that will collect samples at 1 m intervals between a depth of 20 meters and the sea surface. Accuracy  0.05 C. Cost  $200 per float. First tests ongoing. SSS There are a number of scientists interested in making high quality measurements of SSS. This appears to be difficult and perhaps costly and will not be attempted soon.

13. New sensors • Dissolved Oxygen CTD sensors SBE O2 sensor Optode sensor

14. New sensors • Optical/biogeochemical sensors (chlorophyll, carbon cycle, NO3, pH, …) • Acoustic wind/rain gauges Rainfall and wind speed can be measured acoustically using the spectrum of ambient acoustic noise in the ocean. The float is drifting at a depth of 700 m … Strong seasonal variation

15. New features • Acoustically-tracked profiling floats that can operate under seasonal ice; store profiles during winter and transmit during ice-free seasons • Ice avoidance software • POPS for real-time under ice obs. • New battery packs (APEX +50%) • Alkaline vs. Lithium

16. Hurricanes EM-APEX (T, S, V) • Rapid shallow profiling • Electromagnetic velocity measurement • Iridium transmissionsswitch Argo-mode to rapid-shallow mode if floats cross a hurricane …. • More Info: Thomas Sanford, sanford@apl.washington.edu • CBLAST  project Hurricane Frances, 2004

17. Summary • New sensors use impacts Argo core mission • SST should be feasible • Iridium technology is ready • Float lifetime should be improved with the batteries • “Exotic” sensors should be taken into consideration in the future for other components of the GOOS …