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

ocean control of carbon dioxideCO2-05: BiogeochemicalsimulationsProject leaderRichard Matear – CMARProject staffM Mongin, T Roy, ACE; M Nuñez, L Forbes, UTAS;C Rathbone, T Moore, CMAR; T Trull CMAR/UTASProject AimThrough the development and application ofocean carbon models, we are quantifying theSouthern Ocean uptake of atmospheric CO 2and exploring potential feedbacks of projectedglobal warming on this uptake. The results ofthis research will be vital to predicting the rolethe Southern Ocean will play in absorbing andstoring anthropogenic CO 2in the future and,therefore, how future atmospheric CO 2levels willevolve.• Investigation of possible microbial ecosystemresponses to elevated iron inputs andocean stratification using a model tuned toreproduce seasonal cycles at the Kerfix PolarFrontal Zone time series site suggests that10-fold increases in aerosol iron deliveryare insufficient to induce significant change,but that 100-fold and, especially, 1000-fold increases lead to significant increasesin production and changes in ecosystemstructure. Increased stratification ofthe upper water column in response toapproximately 3-fold decreases in windstresses can induce similar increasesin production, emphasising that lightlimitation is also a key factor in SouthernOcean productivity (Mongin et al., GlobalBiogeochemical Cycles, in review).Key achievements in 2005-06• Simulation of ocean acidification through theend of this century suggests major impactson carbonate-shell forming organisms, andthat the greatest effects are likely to occurin Antarctic waters (in collaboration with US,European, and Japanese researchers, Orret al., Nature, 2005). This work emphasisesthe direct effect of anthropogenic CO 2onmarine ecosystem, which is not dependent onclimate warming.• Assessment of spatial and temporal variabilityof air-sea CO 2exchange in the SouthernOcean from a global ocean circulationand biogeochemical model suggests thatmeasuring uptake with sufficient precision tocapture interannual variability in the net fluxover the whole Southern Ocean will requirean approximate two-fold improvementspatial coverage by observational networks(Lenton et al., Global Biogeochemical Cycles,in review). Further investigation suggeststhat large scale atmospheric dynamics (theSouthern Annular Mode) are importantdrivers of internannual variability (Lentonand Matear, Global Biogeochemical Cycles, inreview).Antarctic Climate & Ecosystems CRC - Annual Report 2005-06 33