KEY POINTS:
HOBART - Not many ships go to sea to offload their cargo. But for the crew of the research vessel Kaharoa, the emptier their ship, the closer they are to going home.
The New Zealand vessel holds the world record for deploying robotic ocean profilers, known as Argo floats, for global climate and oceanographic research.
Standing about 1.5m tall and worth $35,000 each, the aluminium Argo floats send profiles on water salinity and temperature to researchers.
They work like a hot-air balloon, using oil instead of air to dive up to 2km below the ocean's surface.
Every 10 days, they return to the surface to send out the information via satellite technology.
Kaharoa crews have deployed more than 400 of the world's 2573 floats and the ship still holds a 100 per cent success rate with its floats after three years.
The vessel is proving essential to scientists, who hope to build a global climate warning system when 3000 floats are deployed worldwide.
Floats are typically deployed from merchant ships but the 28m Kaharoa, operated by the National Institute of Water and Atmospheric Research, is the only vessel that "fills in the gaps" between shipping channels.
Ship's master Evan Solly said floats deployed from the small Kaharoa had a better survival rate than those thrown from giant container vessels.
"It's not rocket science," he said.
"We've only got to take the boat to fixed positions and throw them over the stern ... but we're careful."
Australian Argo team leader Susan Wijffels said the floats provided regular information that would be otherwise difficult to obtain.
"It's like going from black-and-white TV to colour for us," she said.
Dr Wijffels said the Argo network could provide an accurate picture of global heat content and how it was changing over time.
It also could measure and track global warming, allowing scientists to check their climate-change predictions.
Floats also measured ocean salinity and Dr Wijffels said early results showed "big salinity changes" linked to El Nino.
The Argo network is a project shared by 15 countries, including Australia, the United States and New Zealand.
Crew on the Kaharoa have recently deployed 93 floats between New Zealand and Mauritius.
The final seven floats on board will be deployed on the voyage back to New Zealand, the last of their cargo after 68 days at sea.
All at sea
* Argo floats are robotic ocean profilers.
* They stand about 1.5m tall and are worth $35,000 each.
* Made of aluminium, the floats send profiles on water salinity and temperature to researchers.
* They work like a hot-air balloon, using oil instead of air to dive up to 2km below the ocean's surface.
* Every 10 days, they return to the surface to send out the information via satellite technology.
- AAP
