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oceanresearch Scientists Discover How Carbon Is Stored in the Southern Ocean British and Australian scientists have determined how carbon is drawn down from the surface of the Southern Ocean to the deep waters beneath. Rather than carbon being absorbed uniformly into the deep ocean in vast areas, it is drawn down and locked away from the atmosphere by currents 1,000 kilometers wide, scientists from the British Antarctic Survey (BAS) and Austra- lia's Commonwealth Scientific and Industrial Research Or- ganisation (CSIRO) reported in Nature Geoscience in July. These winds, currents and ocean eddies create localized pathways or funnels for carbon to be stored. "Until now we didn't know exactly the physical process- es of how carbon ends up being stored deep in the ocean," lead author Jean-Baptiste Sallée, of BAS, said. "Now that we have an improved understanding of the mechanisms for carbon drawdown, we are better placed to understand the effects of changing climate and future carbon absorption by the ocean." In 2002, 80 Argo floats were deployed in the Southern Ocean to collect data on temperature and salinity, creating 10 years worth of observations. Due to the size and remote location of the Southern Ocean, scientists have only recent- ly been able to explore the workings of the ocean with Argo floats, which today number 3,000 worldwide. The team also analyzed temperature, salinity and pressure data collected from ship-based CTD profiler observations since the 1990s. Around 40 percent of the annual global CO2 emissions ab- sorbed by the world's oceans enter through this region. The rate-limiting step in the anthropogenic carbon uptake by the ocean is the physical transport from the surface into the ocean interior, CSIRO co-author Richard Matear said. "Our study identifies these pathways for the first time, and this matches well with observationally derived estimates of carbon storage in the ocean interior." Iron-Fertilized Algae Takes Absorbed CO2 Down to Seabed Scientists from the Alfred Wegener Institute for Polar and Marine Research published in July the results of an ocean iron fertilization study that demonstrates a substantial pro- portion of carbon from an iron-induced algal bloom sank to the deep seafloor. Fertilization of the ocean by adding iron compounds into an eddy of the Antarctic Circumpolar Current induced diatom-dominated phytoplankton blooms accompanied by considerable CO2 drawdown in the ocean surface layer, the scientists reported. The bloom developed in a 100-meter- deep mixed layer, which is much deeper than believed to be the lower limit for bloom development. The team used 7 tonnes of iron sulfate to fertilize a patch of 150 square kilometers within an vertically coherent, me- soscale eddy in the Southern Ocean. The iron stimulated the growth of phytoplankton, and the team followed the devel- opment of the resulting bloom for five weeks. "We were able to prove that over 50 percent of the plank- ton bloom sank below 1,000 meters depth, indicating that 78 st / SEPTEMBER 2012 www.sea-technology.com