1. Argo September 2004 The status of the Argo project What is Argo trying to do How is it doing it? What have we achieved so far? What has happened since last year? What impact is Argo having? What are the targets and challenges for the coming years?

2. What is Argo trying to do? Collect a novel global temperature/salinity data set. ( Restricted to ice-free areas, deeper than ca2000m) Make data available in real-time (24hrs) Achieve delayed-mode data quality approaching that of research ship observations Use with other in-situ and satellite data for ocean state estimation and ocean forecasting (GODAE). Document ocean heat and fresh water storage and large scale transport (CLIVAR)

4. How is it trying to achieve this? Array of 3000 autonomous profiling floats. Derived from floats used in WOCE (1990-1998). Collaboration of many countries. All subscribe to global objectives and freedom of data access. Start array in 1999. Completion estimated by end 2006. Its primary impetus comes from the requirements of two projects - GODAE - Global Ocean Data Assimilation - CLIVAR - Climate Variability and Predictability

5. Float technologies Three models SOLO - designed and constructed by SIO (USA) APEX - designed and marketed by WRC (USA) PROVOR - designed and marketed by Martec (France) Two CTD sensor suites FSI (USA) SeaBird (USA) Prototypes being developed Ninja (Japan - JAMSTEC) COPEX (China - IOT) New Martec - 100*2000m cycles, no ballasting

6. How are they deployed? Research ships + Rarely visited area + Technical support available + Ancillary data collection - Few such ships Commercial vessels + Long tracks - Mostly N hemisphere - Need to provide tech support - Vessel won’t stop Aircraft (C-130) + Dedicated mission + Remote area coverage - Logistics (certification) - Higher failure rate? SOLO float deployments Logistical challenge - deploy ~ 800 floats per year NZ RV Kaharoa

7. The Argo data system The system delivers real- time (target within 24hrs) data to users via the GTS and by ftp from two global data centers (GDACs). Delayed-mode data are subject to detailed salinity scrutiny by PIs and in regional centres to correct sensor drift/jump. Target delay is 1 year. DM data are about to be delivered to to GDACs.

8. What have we achieved so far? 1300 floats contributed by 18 countries delivering data. The array is close to 100% complete (3°x3°) in N Atlantic, N Indian and parts of N Pacific. But it is a sparse array! 0°N 30°N 180°W 150°W

9. Data quantity and spatial/temporal distribution The WOCE One time survey 12,000 full depth stations in 8 years Confined to transocean sections

10. How are the data being used? Over 10 operational ocean analysis and forecast centers are using Argo data. Key factors benefits cited are :- Depth penetration (> XBTs) Improved data quality Availability of salinity No seasonality in distribution Uniform spatial coverage Global coverage Wide range of climate science (Nov 2003 Workshop) Air-sea interaction under tropical cyclones ENSO forecasts + other seasonal forecasts Indian monsoon Decadal and anthropogenic change

11. Some Argo-based pre-operational products 0 1 UK Met Office salinity at 300m from operational model. Difference from Levitus Top.Old model. Bottom New model with salinity assimilated Metéo France. Salinity at 1000m by assimilating Argo data.

12. Remaining challenges Improve technology (communications, sensors) Delayed-mode quality control Implement system just agreed Clear backlog Improve and update T/S climatologies Regional data centers Evaluate data Work closely with GODAE Dialogue with users Provide appropriate international infrastructure Entrain new countries - Float providers - Deployment help - EEZ access Outreach - Web sites, brochure, education (SEREAD) Complete the global array (Sustain funding, address N hemisphere bias) Sustain and improve float reliability

13. Argo float failure rates These are based on an exponential (e.g. 0.002 per cycle) failure rate and are a more meaningful measure than float performance being 100% until it fails.

14. The present challenge in context From The Argo Prospectus (N. Smith, 1998) “As with the sampling strategy, there are presently uncertainties concerning the technical development and cost of the floats, concerning telemetry, and relating to deployment. It would be unwise to portray these as solved issues, but it would be equally a poor strategy to delay given the already demonstrated capabilities of the instrument and the compelling scientific and societal justifications for the array. In the following we try to give cost and capability estimates for the present, near-future (Year 2000) and five years hence when presently developing technology should be ready for implementation and GODAE is beginning its intensive, “experiment” phase”.