News and events

Argo - Float of January 2011

The float followed the continental shelf edge around the Greenland and Newfoundland coasts before heading east at 50° N.
The float followed the continental shelf edge around the Greenland and Newfoundland coasts before heading east at 50° N. ©

10 January 2011

The oceans have a major influence on our climate system and cover 70% of the Earth's surface, yet relatively little is known about them. To improve our understanding vital data from previously data-sparse ice-free deep ocean areas are being collected by Argo - an international programme that was established in 2000.

In 2007, Argo achieved its aim to create a global array of over 3000 profiling floats; these provide about 100,000 observations each year.

One UK float, deployed in the North Atlantic during October 2005, has completed 187 cycles and is approaching a complete loop of the North Atlantic sub-polar gyre — a large, permanent, circular rotation of ocean water.  The float continues to supply good profiles and application of the Owens and Wong (2009) calibration method reveals no significant sensor drift over its lifetime. More details of its voyage and the data it has collected are provided below.

Potential temperature (top) and salinity (bottom) as measured by float WMO# 6900388 during its voyage.
Potential temperature (top) and salinity (bottom) as measured by float WMO# 6900388 during its voyage. ©

The overall journey helps illustrate the circulation features in the North Atlantic. In particular the narrow, linear flow around the north of the basin, which contrasts with the turbulent progress of the Gulf Stream in the south. Full size and additional data plots are also available in an Adobe PDF View float wmo#6900388 data plots in Adobe PDF  (2 MB) document.

UK float WMO#6900388 (red) and Canadian float WMO#4900628 (blue) trajectories.
UK float WMO#6900388 (red) and Canadian float WMO#4900628 (blue) trajectories. ©

With over 3000 floats active at any one time, it is inevitable that paths may cross. The final plot shows the path of our float (red) when compared with an Argo Canada float (blue). These are overlain on an annually averaged temperature colour map at 1000 m depth supplied by the UK Met Office FOAM hindcast model.

It appears that our float has followed the north-western arm of the North Atlantic current and may commence a second circuit. Meanwhile the Canadian float has taken an alternative route traveling up the Rockall Trough, another main arm of the current, which carries warm water toward Norway and the Polar regions.

References

Owens W.B., Wong A.P.S., 2009. An improved calibration method for the drift of the conductivity sensor on autonomous CTD profiling floats by theta-s climatology, Deep-Sea Research Part I: Oceanographic Research Papers, 56(3), 450-457.

Schlitzer R., 2010. Ocean Data View, http://odv.awi.de

BODC act as the data centre for UK floats in the Argo programme, regardless of their location. We also act as the Regional Data Centre for the Southern Ocean in collaboration with the Commonwealth Scientific & Industrial Research Organisation (CSIRO), Australia.


Related BODC pages

More news and events       More about Argo at BODC
UK Argo float data        

Related external links

International Argo Information Centre (AIC)       UK Hydrographic Office (UKHO)
Other 'floats of the month'       Department for Environment, Food and Rural Affairs (defra)
Met Office       Ministry of Defence (MOD)
National Oceangraphy Centre, Southampton (NOCS)       Commonwealth Scientific & Industrial Research Organisation (CSIRO), Australia