Annual report 2005-06.indd - Antarctic Climate and Ecosystems ...

ocean control of carbon dioxideProgram LeaderAssoc Prof Tom TrullUniversity of Tasmania andCSIRO Marine & AtmosphericResearchThe ocean currently absorbs about onethirdof the carbon dioxide (CO 2) emittedby human activities. This reduces thebuild-up of greenhouse gases in theatmosphere, but makes the ocean moreacidic and may have a major impact onmarine ecosystems.Determining CO 2uptake and its effecton the ocean, and relating this to thelarger goal of predicting human-inducedglobal change, requires considerationof natural climate processes and theirinteraction with the global carbon cycle.New knowledge arising from the ACE CRCOcean Control of Carbon Dioxide Programwill help Australia plan effectively formitigation and adaptation in response toa changing climate.Program Objectives• To determine the current magnitude ofuptake of anthropogenic atmosphericCO 2by the Southern Ocean south ofAustralia. To predict future atmosphericconcentrations of greenhouse gases, we needto know how much CO 2is currently absorbedby the ocean. Work by the ACE CRC iscontributing to an assessment of global oceanuptake and helping quantify relationshipsamong ocean circulation and CO 2transfersbetween the atmosphere and the ocean.• To determine the role of upper oceandynamics in the control of phytoplanktonproduction and biological carbon exportto the deep ocean. ACE CRC researchersare collecting and analysing suspended andsinking marine particles and documenting theecological processes that form and destroythem. These particles redistribute carbon,nutrients and other elements within theocean. Understanding the transfer rates ofthe particles between the surface and thedeep ocean is important for understandingthe contributions of the Southern Ocean tothe control of atmospheric CO 2.• To determine the influence of ironavailability on Southern Ocean planktoncommunity structure and the associatedecosystem control of carbon transferto the deep ocean. ACE CRC scientistsare examining the availability of iron andother micro-nutrients in the Southern Oceanthrough extensive field mapping, samplingand laboratory analyses. Documenting thedistribution of iron in surface and deepwaters, and understanding the processes thatsupply iron and remove it from the SouthernOcean will help us assess the benefits andrisks of proposals to increase biologicalsequestration of carbon through controllediron fertilisation.• To determine the impact of increasingCO 2concentrations on phytoplanktonand on the relative growth rates ofdifferent classes of Southern Oceanphytoplankton. In order to predict thefuture capacity for biological uptake of CO 2into the ocean, we need to understandhow phytoplankton communities andassociated ecosystems will respond toincreased concentrations of CO 2. ACECRC scientists from this program and theAntarctic Climate & Ecosystems CRC - Annual Report 2005-06 27