Argo world 

How well is Argo able to observe the global ocean?

A key objective of Argo is to observe ocean signals related to climate change. This includes regional and global changes in ocean temperature and heat content, salinity and freshwater content, the steric height of the sea surface in relation to total sea level, and large-scale ocean circulation.

The global Argo dataset is beginning to observe global change signals. Seasonal and interannual variability dominate the upper ~600 m of the ocean, but temperature anomalies down to 1900 m show a consistent warming trend. There is now a 10+ year time series of good global coverage, but analyses of decadal changes presently focus on comparison of Argo to sparse and sometimes inaccurate historical data. Indeed, Argo floats only go down to 2000 meters now and the deeper half of the volume of the ocean is not being observed by Argo. Work is being down to develop Deep Argo floats that can measure all the way down to 6000 meters to help answer questions about deep ocean warming. Argo's greatest contributions to observing the global oceans are still in the future, but its global span is clearly transforming the capability to observe climate-related changes.

Over the past 50 years, the oceans have absorbed more than 80% of the total heat added to the air/sea/land/cyrosphere climate system (Levitus et al, 2005). As the dominant reservoir for heat, the oceans are critical for measuring the radiation imbalance of the planet and the surface layer of the oceans plays the role of thermostat and heat source/sink for the lower atmosphere.

Each month, the figure below showing the global average ocean temperature anomaly in the upper 1900 meters based on the gridded RG Argo Climatology (http://sio-argo.ucsd.edu/RG_Climatology.html) is updated.

Global coverage is essential, but for global change applications, Argo data must also have high accuracy and minimal systematic errors. Therefore, a high priority for Argo is to continue work aimed at identifying and correcting pressure measurement errors, especially those with systematic impacts. High quality shipboard CTD transects are critical for assessing data quality in nearby profiling floats.