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 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. 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
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.
14 New sensors Optical/biogeochemical sensors (chlorophyll, carbon cycle, NO3, pH, …) Acoustic wind/rain gauges The float is drifting at a depth of 700 m … Strong seasonal variation Rainfall and wind speed can be measured acoustically using the spectrum of ambient acoustic noise in the ocean.
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 transmissions switch Argo-mode to rapid-shallow mode if floats cross a hurricane …. –More Info: Thomas Sanford, firstname.lastname@example.org email@example.com –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 …