The biogeochemistry and residual mean circulation of the southern ocean

• Main Author: Ito, Takamitsu
• Other Authors: John C. Marshall., Massachusetts Institute of Technology. Technology, Dept. of Earth, Atmospheric, and Planetary Sciences., Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology 2005
• Subjects: Technology; Earth; Atmospheric; and Planetary Sciences; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/1721.1/30290

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005. Includes bibliographical references (p. 233-244). I develop conceptual models of the biogeochemistry and physical circulation of the Southern Ocean in order to study the air-sea fluxes of trace gases and biological productivity and their potential changes over glacial-interglacial timescales. Mesoscale eddy transfers play a dominant role in the dynamical and tracer balances in the Antarctic Circumpolar Current, and the transport of tracers is driven by the residual mean circulation which is the net effect of the Eulerian mean circulation and the eddy-induced circulation. Using an idealized, zonally averaged model of the ACC, I illustrate the sensitivity of the uptake of transient tracers including CFC11, bomb-[Delta]¹⁴C and anthropogenic CO₂ to surface wind stress and buoyancy fluxes over the Southern Ocean. The model qualitatively reproduces observed distribution of CFC11 and bomb-[Delta]¹⁴C , and a suite of sensitivity experiments illustrate the physical processes controlling the rates of the oceanic uptake of these tracers. The sensitivities of the uptake of CFC11 and bomb-[Delta]¹⁴C are largely different because of the differences in their air-sea equilibration timescales. The uptake of CFC11 is mainly determined by the rates of physical transport in the ocean, and that of bomb-[Delta]¹⁴C is mainly controlled by the air-sea gas transfer velocity. Anthropogenic CO₂ falls in between these two cases, and the rate of anthropogenic CO₂ uptake is affected by both processes. Biological productivity in the Southern Ocean is characterized with the circum- polar belt of elevated biological productivity, "Antarctic Circumpolar Productivity Belt". (cont.) Annually and zonally averaged export of biogenic silica is estimated by fitting the zonally averaged tracer transport model to the climatology of silicic acid using the method of least squares. The pattern of export production inferred from the ...