Valiant crew of NIWA’s Kaharoa set to spend Christmas in wild waters

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NIWA’s 28-metre research vessel Kaharoa will spend Christmas at sea. Kaharoa will be in the midst of the Indian Ocean, on an epic journey deploying over 100 ocean-profiling ‘Argo’ floats.

“The crew make a big commitment. It takes a certain sort of person, and they seem to love it. After this voyage Kaharoa will have deployed 750 floats – that is more than any other ship,” says NIWA research oceanographer Dr Phil Sutton.

Argo began in 2000 and this is the tenth Kaharoa trip since 2004. Argo programme leader Professor Dean Roemmich of Scripps Institution of Oceanography (San Diego, USA) says “without Kaharoa, there would not be a global Argo array today.”

The 82-day journey will take the crew of five in a loop from Wellington to Freemantle then to Durban in South Africa through some of the world’s roughest waters: the Pacific and Indian Oceans. Kaharoa mainly deploys floats in the Southern Hemisphere – in the most seldom visited and remote parts of the ocean. The ship will return in mid-February 2010.

Argo is an observation system for the Earth's oceans. It consists of over 3000 small, drifting oceanic robotic probes deployed worldwide. The probes descend as far as 2000 metres, before rising back to the surface profiling the temperature, pressure, and salinity of the water on the way. They do this every ten days. This measures the state of the ocean, and allows currents to be calculated. The data are transmitted to scientists on shore via satellite.

Findings based on data from Argo floats indicate that the upper ocean has been getting saltier in the past two decades. This is consistent with climate model predictions.

"Comparing Argo data with measurements made from ships in the early 1990s indicates that some of the largest changes in the world's oceans have occurred at about latitude 40 degrees south. There was warming at those latitudes, focused towards the western side of each ocean basin. This places New Zealand in the middle of one of the strongest regions for ocean warming between 1990 and the mid 2000s," says Dr Sutton.

For comment, contact:

Dr Phil Sutton

NIWA Research Oceanographer

Tel: + 64 4-386 0386

Background information on Argo floats

Why does NIWA keep deploying Argo floats?

There are about 3,200 Argo floats currently adrift at sea, as evenly spaced as possible over the ice-free surface of the world’s oceans. That is, about one float every three degrees of latitude and longitude around the globe.

The Argo floats themselves are powered by batteries which have a life expectancy of five years. They must be replaced when they leak, fill with water, go missing or even run aground. Then NIWA, and other Argo partners, come to the rescue.

600 floats must be replaced to maintain the status quo a year.

How much does an Argo float cost?

Each float is worth about NZ $25,000.

How are Argo data being used?

There are many different uses for Argo data. All data are available free: anyone can download data from two global data servers (in France and the USA). For more detail, see www.argo.ucsd.edu

Thirteen operational weather and climate centres are currently using the data. For example, Argo data can be combined with satellite altimetry (measure of sea surface height) to improve predictions of hurricane intensity. The data can help improve understanding of variations such as El Niño.

Why do we need Argo data

Lack of sustained observations of the atmosphere, oceans, and land have hindered the development and validation of climate models. Scientists and decision-makers need information about global change and its regional impacts. In response, a key objective of Argo is to observe ocean signals related to climate change.

Scripps deployment of floats

There are several slightly different designs for Argo floats. The ones from Scripps Institution of Oceanography are unusual because they are usually deployed inside their cardboard packaging!

The Scripps floats are packed in biodegradable cardboard boxes that open in the ocean to release the float. Floats are "started" up to prepare them for deployment before the voyage begins. Once at sea, a technician readies the box for deployment and, at predetermined locations, eases it over the stern into the ocean to launch the float.

Partners and funding

NIWA is a partner in the Argo voyages.

There are 23 countries involved in the deployment of Argo floats.

The funding of Kaharoa missions is shared between US Argo (supported by NOAA) and NIWA. Scripps Institution of Oceanography UCSD, the University of Washington, and NIWA provide floats to be deployed by Kaharoa. This current mission also has funding from CSIRO Australia.

The vessel also deploys surface drifters for the Global Drifter program.

Argo is a major contributor to the World Climate Research Program’s Climate Variability and Predictability Experiment (CLIVAR) project and to the Global Ocean Data Assimilation Experiment (GODAE). The Argo array is part of the Global Climate Observing System/Global Ocean Observing System (GCOS/ GOOS). The project is overseen by an International Argo Steering Team and a Data Management Team that are comprised of representatives of float-providing countries. The array's growth is monitored by the Technical Coordinator at the Argo Information Center (AIC) in Toulouse.

Christmas onboard RV Kaharoa, right to left: Peter Rodley, Paul Pascoe, Carol McCormack, Daniel Jones, Lindsay Copland, Mike Naidanovici. (Photo: NIWA)
Research subject: Oceans