[M-IS14] Paleoclimatology and paleoceanography

[MIS14-29] A theoretical study of the marine biogeochemical cycles during the Paleocene-Eocene Thermal Maximum using a one-dimensional vertical ocean model

*Tamaki Rina¹ (1.The University of Tokyo)

The Paleocene-Eocene Thermal Maximum (PETM) was a significant warming event that occurred approximately 56 Ma (million years ago). Geological studies have shown that the carbon isotope ratio (δ13C) decreased by 2–3‰ over about 10,000 years, and that the difference in δ13C between surface water and deep water also decreased. These studies have also indicated that the collapse of methane hydrates introduced isotopically light carbon into the atmosphere and ocean system, and caused both the warming event and the negative carbon isotope excursion. The PETM has been drawing attention as an analogy for current global warming. However, there are few quantitative studies on how marine geochemical cycles and marine biological activities changed during the PETM.
Therefore, in this study, we developed a one-dimensional vertical ocean model to investigate marine biochemical cycles during the PETM. In this model, carbon, phosphorus, and calcium cycles are considered, allowing for quantitative examination of the marine biogeochemical cycles. The results indicate that an increase in upwelling rate or a decrease in primary production leads to a decrease in the δ13C difference between ocean surface and deep water. The results also indicate that primary production may not have been limited by phosphorus during the carbon isotope excursion.