Data-gathering floats provide a clearer picture of how temperature rise affects the oceans.

Hundreds of robotic instruments deployed across the South Pacific have begun to reveal dramatic new insights into the impact of climate change upon oceans in our corner of the world.

One of the world's leading oceanographers, Professor Dean Roemmich, is basing himself in Wellington as he analyses the earliest indicators from a decade of data collected by a range of instruments called Argo floats.

About 3700 of the torpedo-like floats have been deployed across the world's oceans, with hundreds of them transmitting data from the South Pacific in near-real time to satellites.

Information from the floats, which sink to about 2000m below the surface and measure temperature and salinity, enables scientists to observe large-scale changes across oceans - ultimately improving climate predictability and modelling. There are now enough of them to measure every degree of latitude and longitude of the world's oceans four times a year.


Professor Roemmich, of the University of California's Scripps Institution of Oceanography, told the Herald he and colleagues had observed an ongoing trend of change in the South Pacific Gyre - a mass of circular currents that rotate anti-clockwise and dominate the circulation of the South Pacific Ocean.

The amount of water being transported by the gyre over the past decade had increased about 10 per cent - the same rate observed in each of the two decades previously - and Professor Roemmich suspected this was mainly being driven by winds.

While temperature and salinity changes are relatively clear, changes in the currents forming the large-scale ocean circulation are more difficult to define. However, a clear signal is emerging.

Professor Roemmich said the changes so far seen in ocean circulation were linked to climate change, which had contributed to a heavily evidenced warming of oceans over the past 50 years.

Now the Argo programme was being expanded to measure conditions at the lowest depths of the ocean.

Without the contribution of Niwa, which has deployed about 1200 floats from its Kaharoa vessel, the Argo programme could not have succeeded, Professor Roemmich said. "New Zealand has been absolutely critical for achieving a global array."