Glacial‐interglacial CO2 change: The Iron Hypothesis
Tóm tắt
Several explanations for the 200 to 280 ppm glacial/interglacial change in atmospheric CO2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients. An hypothesis is presented herein in which arguments are made that new productivity in today's southern ocean (7.4 × 1013g yr−1) is limited by iron deficiency, and hence the phytoplankton are unable to take advantage of the excess surface nitrate/phosphate that, if used, could result in total southern ocean new production of 2−3 × 1015 g C yr−1. As a consequence of Fe‐limited new productivity, Holocene interglacial CO2 levels (preindustrial) are as high as they were during the last interglacial (≈ 280 ppm). In contrast, atmospheric dust Fe supplies were 50 times higher during the last glacial maximum (LGM). Because of this Fe enrichment, phytoplankton growth may have been greatly enhanced, larger amounts of upwelled nutrients may have been used, and the resulting stimulation of new productivity may have contributed to the LGM drawdown of atmospheric CO2 to levels of less than 200 ppm. Background information and arguments in support of this hypothesis are presented.
Từ khóa
Tài liệu tham khảo
Bainbridge A. E., 1981, CEOSECS Atlantic Expedition: HydrographLc Data, 1972–73
Broecker W. S., 1982, GEOSECS Pacific Expedition: Hydrographie Data, 1973–1974
Cooke D. W., 1982, Antarctic Geoscience, 1017
El‐Sayed S. Z., 1988, Productivity of the southern ocean: A closer look, Comp. Biochem. Physiol., 9, 489
Hardy A. C., 1967, Great Waters
Hart T. J., 1934, On the phytoplankton of the south‐west Atlantic and the Bellingshausen Sea, 1929–31, Discovery Rep., 1
Hart T. J., 1942, Phytoplankton periodicity in Antarctic surface waters, Discovery Rep., 261
Liebig J., 1847, Chemistry in Its Application to Agriculture and Physiology
Morel F. M. M., 1985, Chemical Processes in Lakes, 251
Neftel A., 1982, Ice core sample measurements give atmospheric C02 content during the past 40,000 years, Nature, 295, 220, 10.1038/295220a0
Weiss R. F., 1983, GEOSECS Indian Ocean Expedition: Hydrographie Data, 1977–1978
Whitworth T., 1988, The Antarctic Circumpolar Current, Oceanus, 31, 53