What is Argo?

In 2000, the international Argo observational program was launched by the IOC and WMO to observe the global in situ ocean temperature and salinity, in order to monitor the ocean's variability and understand its role in climate. To reach this scientific goal, the pre-requisite was to provide in near-real time profiles of ocean state parameters every 10 days for each 3x3 degrees area of the global ocean. This corresponds to about 3000 floats operating permanently at sea (Riser et al., 2016). Given the autonomous floats technology available at the beginning of the program in 2000, parameters were limited to temperature and salinity, sampling depth was limited to the first 2000m of the water column and sampling area was limited to the open ocean, away from marginal seas as well as high latitudes. It took about 8 years to the international community to reach this sampling target (from 2000 to the end of 2007). Then, more than ten years later (2018), more than 2 millions quality controlled profiles have been provided, overwhelming in one decade the amount of profiles ever carried out in the history of oceanography. In addition to the major increase in high quality data quantity due to Argo, the historical northern hemisphere and near-coastal biases are greatly reduced in the much more uniform global sampling. Argo also has rectified a major seasonal bias in sampling, particularly in the polar oceans. It is thus not surprising that the Argo program is now the backbone of in situ Global Ocean Observing System (GOOS) and hence revolutionizes our vision and understanding of the ocean in unexpected ways days after days.

Argo float deployment

The international Argo program aims to build and sustain a global real-time observational network of in-situ measurements integrated to other observational systems of the Earth in order to:

  • observed climate variability from the seasonal to decadal timescale and to observe climate change of the oceans. This includes regional and global changes in oceanic heat, fresh water content, sea surface steric height and large scale circulation.
  • provide observations for calibration and validation satellite remote measurements.
  • provide observations to initialize and constraint numerical model simulations and operational ocean forecasting systems.
  • promote new parameters and observation sites (biogeochemical parameters, deeper layers, high latitude, marginal seas) to foster emergence of a interdisciplinary in situ network measurement (physic, biogeochemical,…) to fill the observational gab of the core-Argo mission.

Argo floats global network