海底堆積物に記録された炭素循環の記録とミランコビッチサイクル

概要

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Several hundred years of astronomical observations have left no doubt that the Earths orbit is subject to cyclic variations. While the annual energy receipt of solar radiation over the Earth as a whole is not change, the distribution of this energy, by latitude and by season, is affected by three parameters: an obliquity cycle of 41kyr, an eccentricity cycle of a quasi-period of 100kyr, and a precession cycle of 26kyr. The variance spectrum of the records of foraminiferal δ18O and magnetic susceptibility from Indian Ocean and organic carbon percentage from the equatorial regions of Pacific and Atlantic Oceans shows the well-documented concentrations of power at the orbital periodicities of 100kyr, 41kyr and near 23 and 19kyr. On the other hand, the resolution of the precessional bands in carbonate dissolution index is much less clear than those of obliquity and eccentricity bands. These results show that orbital forcing of global climate has strongly affected global carbon cycle. Detailed analysis of coherency and phase spectrum between δ18O and carbon-related data (i. e., carbon contents and isotopic composition) will improve our understanding global carbon cycle.
社団法人東京地学協会の論文