Browsing by Subject "Southern Ocean"

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    Antarctica’s Dry Valleys: A potential source of soluble iron to the Southern Ocean?
    (AGU, 2015-03) Bhattachan, Abinash; Wang, Lixin; Miller, Molly F.; Licht, Kathy J.; D'Odorico, Paolo; Department of Earth Sciences, IU School of Science
    The soluble iron content and dust emission potential of sediment samples collected from the Taylor Valley in the McMurdo Dry Valleys (MDVs) and sea ice in the McMurdo Sound were evaluated to determine whether inputs to the Southern Ocean may be sufficient to affect ocean productivity. Our results show that the dust-generating potential from the MDVs soils are comparable to those of sediments from other major dust sources in the Southern Hemisphere. Sediments from the MDVs and sea ice are one order of magnitude richer in soluble iron than those in other dust sources in the Southern Hemisphere. Forward trajectory analyses show that the dust from the MDVs is likely to be deposited in the Southern Ocean. These results provide evidence of the possible supply of soluble iron to the Southern Ocean associated with dust transport from the MDVs, should climate change expand the exposed areas of the continent.
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    The “White Ocean” Hypothesis: A Late Pleistocene Southern Ocean Governed by Coccolithophores and Driven by Phosphorus
    (Frontiers Media, 2012-07-02) Flores, José-Abel; Filippelli, Gabriel M.; Sierro, Francisco J.; Latimer, Jennifer; Earth and Environmental Sciences, School of Science
    Paleoproductivity is a critical component in past ocean biogeochemistry, but accurate reconstructions of productivity are often hindered by limited integration of proxies. Here, we integrate geochemical (phosphorus) and micropaleontological proxies at millennial timescales, revealing that the coccolithophore record in the Subantarctic zone of the South Atlantic Ocean is driven largely by variations in marine phosphorus availability. A quantitative micropaleontological and geochemical analysis carried out in sediments retrieved from Ocean Drilling Program Site 1089 (Subantarctic Zone) reveals that most of the export productivity in this region over the last 0.5 my was due to coccolithophores. Glacial periods were generally intervals of high productivity, with productivity reaching a peak at terminations. Particularly high productivity was observed at Termination V and Termination IV, events that are characterized by high abundance of coccolithophores and maxima in the phosphorus/titanium and strontium/titanium records. We link the increase in productivity both to regional oceanographic phenomena, i.e., the northward displacement of the upwelling cell of the Antarctic divergence when the ice-sheet expanded, and to the increase in the inventory of phosphorus in the ocean due to enhanced transfer of this nutrient from continental margins during glacial lowstands in sea level. The Mid-Brunhes interval stands out from the rest of the record, being dominated by the small and highly calcified species Gephyrocapsa caribbeanica that provides most of the carbonate in these sediments. This likely represents higher availability of phosphorus in the surface ocean, especially in mesotrophic and oligotrophic zones. Under these condition, some coccolithophore species developed an r-strategy (opportunistic species; growth rate maximized) resulting in the bloom of G. caribbeanica. These seasonal blooms of may have induced “white tides” similar to those observed today in Emiliania huxleyi.