海洋生物化学炭素循環モデルを用いた暁新世／始新世境界温暖化極大イベントにおける炭素循環変動の復元

Abstract

The Paleocene/Eocene thermal maximum (PETM) is an event characterized by abrupt warming, negative excursion of carbon isotopic composition, and extinction of benthic foraminifera, and is considered to have been caused by the release of a large amount of methane and/or carbon dioxide from methane hydrate. In this study, we try to reconstruct changes of the marine carbon cycle during that period using a one-dimensional marine carbon cycle model and the data set of marine carbon isotopic composition. We find that the bioproductivities of organic carbon and carbonate, and the global mean upwelling rate rapidly increased at the carbon isotope excursion event. The lower level of the carbon isotopic composition observed after the excursion event probably resulted from a large quantity of light carbon remaining in the ocean. These results can be interpreted as follows : the warming of climate intensifies vertical mixing of the ocean, so large quantities of nutrients are supplied to the surface water from the intermediate water, resulting in an increase in the bioproductivity at PETM.