Largest-ever deployment of ocean floats
The NIWA vessel, Kaharoa, is setting sail on a 90-day voyage to deploy high-tech floats between New Zealand and Peru.
Kaharoa will carry 84 floats, which is the largest number ever deployed in a single voyage. Each float is worth about $20,000, making the total worth over $1.6 million.
The floats can help scientists measure global warming, predict the strength of tropical cyclones, and even get a better fix on the path of toxic algal blooms.
“Many people don’t realise that both the ocean and the atmosphere are important for controlling the climate over the long-term,” says NIWA oceanographer, Dr Philip Sutton. “We need to know what’s happening in the oceans just as much as we need weather-balloons and other atmospheric-observing tools.”
The route will take Kaharoa – which is 28 metres long – through the Tasman Sea to Tahiti, then most of the way to Peru, and back.
Each float sinks to a depth of 1000 metres and parks there, carried along by ocean currents. After nine or ten days, it sinks further to between 1250 and 2000 metres, then rises to the surface, measuring the temperature and salinity of the water on the way up. Once on the surface, the float transmits data and its location via satellite.
The voyage is a joint collaboration between NIWA, the Scripps Institution of Oceanography (San Diego), and the University of Washington (Seattle). It is part of a global programme called Argo, which aims to deploy and maintain 3,000 floats by early 2007.
Two of the world leaders of Argo, Dr Dean Roemmich of Scripps and Dr Steve Riser of the University of Washington, have been in Wellington to prepare the floats, along with a team of New Zealand and United States float engineers.
“If you want to observe global warming, the ocean is the place to look because it’s absorbing more than 90% of the additional heat,” says Dr Roemmich.
“At first look, the floats deployed by Kaharoa between here and Chile are confirming that the sea along the route is becoming less salty. That’s consistent with global warming, where temperate regions get more rain and so the upper layers of the ocean have more fresh water in them.
“Another example of Argo’s use is in tropical cyclones,” says Dr Riser. “In the Atlantic, we’ve now had 140 cases where a hurricane has travelled over an Argo float. Such storms suck heat out of the ocean – the floats have measured up to a one degree Celsius drop in temperature even at depths of 100 to 150 metres.”
“In future, computer models for forecasting cyclones could incorporate data about the temperature of the upper ocean – not just the sea surface – and so predict more accurately how strong a storm will become,” says Dr Roemmich.
To view the current global float status and for more information about ARGO worldwide, see www.argo.ucsd.edu/index.html
