Dr. Thomas William TRULL
Senior Principal Research Scientist
Commonwealth Scientific and Industrial Research Organization, Australia
PhD., Oceanography, Massachusetts Institute of Technology – Woods Hole Oceanographic Institution Joint Program 1989
i. The Southern Ocean Time Series is a set of deep ocean moorings southwest of Tasmania, serviced just once a year, measuring >150 parameters important to climate and carbon cycle processes. Recent results for the full seasonal pCO2 cycle with hourly resolution reveal that the biological carbon pump is as effective in these high-nutrient low-chlorophyll (HNLC) Subantarctic waters as in North Atlantic high-chlorophyll spring bloom waters. Current work is attempting to determine the role of community ecology in this effectiveness, using detailed information on 4 biogeochemical compartments (nutrients, phytoplankton, zooplankton, detritus) collected by the moorings.
ii. Biogeochemical-Argo autonomous profiling floats equipped with phytoplankton fluorometers and oxygen sensors were used to track the impact of natural iron fertilization for 1000 km downstream of the Kerguelen plateau in the Southern Ocean, and reveal that biomass exceeds that visible from satellite remote sensing and involves a community with high export efficiency. Interpreting the biomass distributions in a Lagrangian framework suggests iron removal in winter is a key control on the overall impact on the carbon cycle.
iii. the ecosystem service of CO2 uptake comes at the cost of acidification impacts, particularly on carbonate forming organisms. Remote sensing has inferred the presence of a potentially susceptible “Great Calcite Belt’ of coccolithophores in the Southern Ocean, but semi-automated sampling from Antarctic resupply ships suggests this is over-estimated south of Australia, especially in polar waters where these organisms appear to contribute only ~1 % of phytoplankton biomass.
These investigations were carried out by the Antarctic Climate and Ecosystems Cooperative Research Centre - the talk will start with an introduction to its international partnerships.