Understanding the Southern Ocean is important not only to improving weather forecasts for Australia.
The region surrounding Antarctica is also a"modulator of the global climate",said Cai Wenju,director of CSIRO's new Centre for Southern Hemisphere Oceans Research that is also a partner of the Investigator's research.
While oceans globally take up about 93 per cent of the extra heat trapped in the atmosphere by greenhouse gases,they also absorb about a third of the extra carbon-dioxide released by human activities,such as burning coal.
Of those totals,the Southern Ocean accounts for as much as 75 per cent of the ocean heat sink and 40 per cent of the CO2 dissolved in the seas,Dr Rintoul said.
“Changes in the[deep ocean] circulation would alter the efficiency that the Southern Ocean takes up heat and carbon,and have a big impact on climate,” he said.
Dr Rintoul said the salinity changes detected may be a response following the breaking off of half the Merz Glacier Tongue in 2010 in eastern Antarctica.
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“The big step in[bottom water] freshening that happened in 2010 after the calving of the Merz Glacier may now be recovering after the sea ice distribution changed again,"he said.
The drop in sea ice coverage from a record large extent about four years ago to record - or near record - low coverage this year may also be a factor,he said.
According to Jan Lieser,a sea ice expert at the ACE CRC,sea ice levels as of February 17 were the lowest in accurate satellite records going back to 1981 for this date,at about 2.17 million square kilometres.
The melting season is nearing its end,and it remains to be seen whether coverage will drop below the record minimum set last March,Dr Lieser said.
The RV Investigators'researchers also collected samples of key ocean nutrients,such as iron.
They also monitored cloud formation with a special NASA plane making regular flights overhead when conditions were ideal.
The interaction between clouds and aerosols,and their role in future global warming,is one of the largest uncertainties in climate models,CSIRO said.
Air over the Southern Ocean is relatively pristine compared with other regions of the world,with the source of aerosols mainly organic material produced by tiny phytoplankton,Dr Rintoul said.
The scientists had collected"a fantastic data set"of aerosols using a combination of instruments based on the vessel,in the aircraft and from satellites,he said.