A topic of persistent interest in the Atlantic Ocean is the meridional overturning circulation. This circulation finds its origins in deep convection in the Labrador and Norwegian/Greenland Seas, which are the coldest and freshest basins of the North Atlantic. Yashayaev and Loder (2008) used Argo data to simulate a station in the central Labrador Sea. Using this technique they were able to monitor the onset and development of deep convection exceeding 1600m resulting in the voluminous production of Labrador Sea Water. This was a surprise after a decade of much less intense convection. The relation of the onset of convection in the Labrador Sea to atmospheric conditions is described by Sproson et al (2008) and the implications of these surprising observations was reviewed by Våge et al (2009).
A transatlantic section at 24°N in the Atlantic Ocean has been occupied in 1957, 1981, 1992, 1998 and 2004. Using these data, Bryden et al (2005) suggested that the Atlantic meridional circulation had slowed by 30% over this period. This contrasts with the computations of Vélez-Belchi et al (2008) and Hernández-Guerra et al (2008) which used Argo data to create synthetic versions of this section. These have been analyzed using inverse theory and deep velocities estimated from Argo float trajectories (Lebedev et al 2007) and suggest that the meridional overturning circulation has not changed significantly since 1957.
Argo observations in the Indian Ocean are creating new insights from many different authors on a variety of subjects. Argo is enabling a new understanding of the upper ocean variability of the Arabian Sea, such as summer cooling during contrasting monsoons (Vinayachandran, 2004), temporal variability of the core-depth of Arabian Sea High Salinity Water mass (ASHSW) and the origin of this water mass (Joseph and Freeland, 2005).
Additionally, Argo data have been used to examine buoyancy flux variations and their role in air sea interactions (Anitha et al, 2008), identification of the low-salinity plume off the Gulf of Khambhat, India, during the post-monsoon period, mixed layer variability of western Arabian Sea (Bhaskar et al, 2006) and seasonal variability of the barrier layer (Thadathil et al, 2008).
The importance of upper ocean temperature and salinity structure during a cyclone was illustrated by McPhaden et al (2009). Chowdary et al (2009) used Argo profiles to reveal a pronounced westward propagation of subsurface warming in the southern tropical Indian Ocean associated with Rossby waves on the sloping thermocline. Using Argo and satellite observations, Vinayachandran and Saji (2008) found intense cooling of the sea surface at intraseasonal time scales in the southern tropical Indian Ocean during austral summer.
Within the Pacific Ocean, Argo is allowing new views of water mass formation (Oka, 2009), properties of mesoscale eddies (Qiu and Chen, 2005), and the response of the upper ocean to cyclone forcing (Liu et al, 2006). Also in the Pacific is where there is evidence of the impact of Argo observations on fisheries management (She et al, 2006, Yang et al, 2009 and Irvine and Crawford, 2008).
The western boundary current extension regions have been observed by Argo in both the Atlantic and Pacific Oceans, but the Kurishio Extension Region has had double the density of floats compared with the Gulf Stream Extension Region and the Argo plan. This occurred as a result of the intense Kuroshio Extension System Study (KESS). Cronin et al (2009) discuss observations of ocean-atmosphere interactions in western boundary current extensions, presenting a case for increased float density to the levels that resulted from float deployments in support of KESS. The primary object of such an increased density would be to map ocean atmosphere heat exchange over spatial scales of about 100 km.
Argo is clearly set apart from previous studies by the global coverage and especially the effort made to sample the northern and southern hemispheres without bias. This wealth of new data is allowing a thorough examination of the Southern Ocean and its variability for the first time. When Argo began it was limited to the area between 60°S to 60°N. Changes in technology now allow us to consider extending the range of Argo to higher latitudes (van Wijk et al, 2009).
One result of more data is the possibility to assess the mixed-layer heat budget in the Southern Ocean (Dong et al, 2007). Gille (2008) compared Argo temperature observations with spatially co-located profiles from the previous seventy years and identified multi-decadal warming trends. Gille observes that although the data do not preclude the possibility that the Southern Ocean has warmed as a result of changes in heat fluxes, the trends suggest a poleward migration of the Antarctic Circumpolar Current.