In brief: Kaharoa’s Argo cargo
In October, NIWA research vessel Kaharoa set out across the South Pacific with a cargo of Argo floats.
Over two months, the crew placed 120 of the remote sensing instruments between latitudes 28 and 46 degrees South, between New Zealand and South America, adding them to some 3500 floats already recording real-time data worldwide, for use in climate, weather, oceanographic and fisheries research.
The two-metre-high robotic probes usually drift about 1000 metres down, for about nine days. Then they automatically descend to profiling pressure – often as deep as two kilometres – before rising, profiling water temperature, pressure and salinity as they go.
The data are transmitted via satellite every ten days to scientists ashore, and the satellites determine how far each float has drifted, before the process begins again. Around 800 new Argos are deployed each year globally, and their data is freely available to all.
One of the programme leaders, Dr Dean Roemmich of the US Scripps Institution of Oceanography, says Japanese and US scientists are now testing Argos capable of descending to four, or even six kilometres. "Argo data are invaluable for informing governments, science and the community on inter-annual variability such as El Niño, as well as decadal and multi-decadal changes in the global ocean."
During this, Kaharoa's 13th Argo voyage, floats were placed on behalf of Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), Scripps and the University of Washington. A further two were deployed for NIWA.
On its return, the vessel will have deployed a total of 1100 floats since the programme's inception back in 1999, more than any other vessel. Twenty seven countries are involved in the project.