HR: 11:20h
AN: A52A-05 INVITED     [Abstracts]
TI: Interactions between Dust Aerosols and Ecosystems in the Global Oceans
AU: * Gregg, W
EM: watson.gregg@nasa.gov
AF: NASA/GSFC/GMAO, Code 610.1, Greenbelt, MD 20771, United States
AB: Iron is an important micro-nutrient for phytoplankton in the oceans. Iron is brought to the surface layers of the ocean, where most of the phytoplankton live, from the deep ocean, the coasts, and, most importantly, by soil dust aerosols. Since phytoplankton represent the base of the food web, dust aerosols play a role in ocean ecosystem structure, function, and variability. Since the distribution of dust aerosols, and deposition of iron from them, is variable in time and space, so is the importance of dust aerosols for ocean ecosystems. Using a coupled three-dimensional biogeochemical model of the global oceans, we investigated the relationships between dust aerosols and ocean ecosystems. By varying the amount of iron deposition deriving from dust, we can quantify the local, regional, and global effects on ocean phytoplankton, ecosystems, and primary production. In the most extreme experiment, all dust aerosol deposition was ceased for 25 years. Reduction in dissolved iron concentrations was greater than 60 per cent. Phytoplankton populations nearly disappeared in the central ocean gyres. A 10 per cent decline was observed in the North Pacific. But surprisingly, global chlorophyll concentrations did not change, and global primary production declined by only about 3 per cent. Losses incurred by reduced dissolved iron were compensated by increased nitrate, enhancing nitrogen- limited ecosystems at the expense of iron-limited ecosystems. These results show the importance of regional variability in the relationship between dust aerosols and ocean ecosystems.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly