OK, I'm certainly not a physicist, so my confusion is increasing with the length of this thread :(
Is/has the southern ocean warmed in recent decades, or not? And given the now accepted vortexes discovered in the southern ocean, how is it that the CO2 and be sucked to greater depths, but not the warmth from the upper layes?
I also think there is growing evidence that changes, be they at the surface initially, are definitely having an impact on deeper Antarctic waters. For instance:
May 21, 2012
reduction in the amount of Antarctic Bottom Water found off the coast of Antarctica. Comparing detailed measurements taken during the Australian Antarctic program's 2012 Southern Ocean marine science voyage to historical data dating back to 1970, scientists estimate there has been as much as a 60 per cent reduction in the volume of Antarctic Bottom Water, the cold dense water that drives global ocean currents.
In an intensive and arduous 25-day observing program, temperature and salinity samples were collected at 77 sites between Antarctica and Fremantle. Such ship transects provide the only means to detect changes in the deep ocean.
The new measurements, which have not yet been published, suggest the densest waters in the world ocean are gradually disappearing and being replaced by less dense waters.
"The amount of dense Antarctic Bottom Water has contracted each time we've measured it since the 1970s," said Dr Steve Rintoul, of CSIRO and the Antarctic Climate and Ecosystems CRC. "There is now only about 40 per cent as much dense water present as observed in 1970."
The ocean profiles also show that the dense water formed around Antarctica has become less saline since 1970.
"It's a clear signal to us that the oceans are responding rapidly to variations in climate in polar regions. The sinking of dense water around Antarctica is part of a global pattern of ocean currents that has a strong influence on climate, so evidence that these waters are changing is important," Dr Rintoul said.
The research was carried out by more than 50 scientists on the Australian Antarctic Division's research and resupply vessel Aurora Australis, which sailed to Commonwealth Bay, west along the Antarctic coast, and returned into Fremantle.
The Australian Antarctic Division's Chief Scientist, Dr Nick Gales, said the findings of the oceanographic study are profoundly important.
"Not only will this research improve our understanding of ocean currents, but will also feed into our knowledge of how the Southern Ocean and the Antarctic continent drives the world's climate processes," Dr Gales said.
Dr Rintoul was Chief Scientist on the recent voyage and has made a dozen voyages to the Southern Ocean. "When we speak of global warming, we really mean ocean warming: more than 90 per cent of the extra heat energy stored by the earth over the last 50 years has gone into warming up the ocean.
The Southern Ocean is particularly important because it stores more heat and carbon dioxide released by human activities than any other region, and so helps to slow the rate of climate change" Dr Rintoul said. "A key goal of our work is to determine if the Southern Ocean will continue to play this role in the future."
While the final analysis is yet to be completed by his team, Rintoul believes increased melt of floating glacial ice is likely to be the largest contributor to these salinity changes.
“Changes in snowfall or sea ice seem to be too small or have the wrong distribution to explain the changes we have measured in the deep ocean.
“The composition of the water also provides a clue: water that comes from melting glacial ice has a particular isotope signature, allowing us to track input of melt water. The isotopic measurements back up the story that there’s been an increase in the amount of melting of floating glacial ice around the edge of Antarctica,” he says.