Ocean robots set course to the middle of nowhere
NIWA Media Release 19 June 2007
Ocean robots
set course to the middle of nowhere
NIWA’s 28-metre long research vessel Kaharoa, will spend the next month deploying high tech ocean-profiling floats in the mid-Pacific. The 28–30 day journey will take the crew of five in a loop from Wellington up towards French Polynesia then back to Auckland without making landfall.
The ‘Argo’ floats measure properties and currents of the upper ocean then surface to beam this data to satellites.
This is RV Kaharoa’s seventh Argo assignment: the ship has deployed more Argo floats than any other vessel in the world. In many places, the floats have been deployed from regular container ships, or even from the air. Neither option is feasible for much of the Pacific, so, in 2004, Scripps Institution of Oceanography (San Diego) and the University of Washington (Seattle) formed a collaboration with NIWA (National Institute of Water & Atmospheric Research) to use RV Kaharoa.
Argo programme leader Professor Dean Roemmich of Scripps Institution of Oceanogaphy says “without Kaharoa, there would not be a global Argo array today.”
Argo data are used by operational weather and climate centres as well as researchers around the world. For the south-west Pacific, Argo data are showing that the ocean east of New Zealand has warmed up faster than the global average for the past 40 years.
RV Kaharoa is currently scheduled to leave Wellington on Wednesday 20 June or Thursday 21 June.
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Background
What Argo floats do: a typical
ten day cycle
How deep a float goes and how long it
spends there is pre-programmed.
In general, Argo floats
first sink to about 1000 metres. At a rate of about 10
centimetres per second, this takes about 6 hours. Floats
usually drift at this depth for about 9 days. They then
descend further, down as far as 2000 metres, before rising
back to the surface profiling the temperature, pressure, and
salinity of the water on the way.
A float will spend
6–12 hours on the surface transmitting data to passing
satellites.
How long does an Argo float
last?
Floats have a lifespan of approximately 4–5
years.
How much does an Argo float cost?
Each
float is worth about NZ$20,000.
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).
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. It’s been suggested that about ten years of Argo
data would be required to get a good indication of longer
term changes in the world’s oceans associated with global
warming.
For more detail, see www.argo.ucsd.edu
ENDS