"Survostral has given us a foundation for much of what is known about the way the ocean in this inhospitable and difficult-to-access region controls the global climate," Rintoul said.

The project leader said sea level rise was not uniform in the Southern Ocean and that rises were not guaranteed to continue at the same rate in the future.

The study had also shown that the Southern Ocean's uptake of carbon dioxide changed with the seasons.

In summer, an increase in phytoplankton brought about by the greater light caused the Southern Ocean to absorb more carbon dioxide from the atmosphere than in colder months, he said.

The study showed that as waters warmed, some species of phytoplankton were extending further south, although more research was needed to determine the importance of this finding.

"What's significant is that we've detected changes in the physical environment and now we're also detecting changes in the biology in response to those physical changes.

"The next challenge is to figure out what these biological changes mean for carbon uptake and for higher levels of the food chain," he said.

Tiny phytoplankton are at the bottom of the food chain and are a crucial food source for a number of species.

Investigations by the L'Astrolabe in the world's largest ocean current between Tasmania and Antarctica had shown that deep streams of water were taking warming deep into the ocean.

"The program started as just measuring temperature and salinity. We've now recently begun a much more comprehensive chemistry and biology program of measurements," Rintoul said.

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