60. Biogeochemical changes in the Southern Ocean, South of Tasmania

Paula C. Pardo (1), Bronte Tilbrook (1,2)

1 Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Tasmania, Australia.
2 Commonwealth Scientific and Industrial Research Organisation, Oceans and Atmosphere, Hobart, Tasmania, Australia.

The Southern Ocean is a region undergoing significant changes in seawater carbonate chemistry with potential to disrupt marine ecosystems. We used data from 8 repeats of the GO-SHIPS SR3 hydrographic section between Tasmania and Antarctica to characterise the evolution of biogeochemical properties in the region. The sections were completed between 1991 and 2011 in all seasons, and cover one of the most frequent repeat sections occupied in the Southern Ocean. An optimum multi-parametric analysis was use to define the major subsurface water mass distributions. The analysis allows us to determine how CO2 system and other biogeochemical properties are changing, including the pH and anthropogenic CO2 content. Key features like the influence of High Salinity Shelf Water that cascades down the continental slope and mixes with deeper waters to produce Antarctic Bottom Water are resolved. We will discuss the observed changes in the major water masses, distinguishing between the natural variability and the possible effects of climate change and relating them to the dynamics in the region.