Dr Gregg Brunskill of the Australian Institute of Marine Science (AIMS) said the petroleum industry and Geoscience Australia had previously observed bubble plumes at the sea surface in the Timor Sea but their composition was unknown. Dr Brunskill was the chief scientist on a major expedition aboard the Marine National Research Facility RV Southern Surveyor which set out to study the Oceanic Shoals, and communities that live on and around natural gas seeps about 300 km north of Broome in seas 90 m deep.
Another task of the voyage was to collect sediment and coral cores in deeper waters 300 km WNW of Darwin.
During the voyage, AIMS organic geochemist Dr. Kathy Burns determined that the bubbles were virtually pure methane - 99%, laced with other hydrocarbons - streaming from the seafloor 100 metres to the surface.
"We estimate, in an area of half a square kilometre, up to a tonne of methane per day is being dispersed into the atmosphere," Dr Brunskill
said methane is 20 times more powerful than CO2 as a heat trapping greenhouse gas, and natural fluxes of methane from the ocean to the atmosphere are possibly significant in the natural greenhouse gas budget.
With initial visions of children chasing bubbles at a party, the idea of using a custom built "submarine bubble catcher" in the ocean had the ship crew doubting the sanity of the scientists prior to its deployment, but all were pleasantly surprised by the outcome." The bubble catcher device successfully measured the gas flux from the sea to the atmosphere as 0.5 to 1 litre of methane per square metre per day, but most of this happened during low tides," he
"We suspect the minerals associated with the seep fluids cause a rapid fossilisation process," said Dr Gregg Brunskill
Sediment cores taken from the Timor
Sea region will be analysed at AIMS
, and will reveal the history of marine sedimentation and oceanography during the last several centuries, and some longer cores will expose a chronicle of ocean and climate variations over the last 10,000 to 20,000 years.
Coral cores were taken from large bommies on top of large mounds."Annual growth bands in the corals can be analysed for isotopes and trace elements that tell us about the past history of seawater temperature and salinity, and perhaps the rate of climate warming, " Dr Brunskill
...Dr Gregg Brunskill, AIMS Biogeochemist, Phone: (07) 4753 4218,