[M-IS18] Paleoclimatology and paleoceanography

[MIS18-P10] Potential link of the Bering straight closure, increasing of deep water CO2 storage, and Mid Pleistocene Transition, noted from stacked Benthic foraminiferal Carbon and Oxygen Isotope evidence of IODP Exp. 323

*Hirofumi Asahi¹, Sev Kender⁶, Minoru Ikehara¹, Yusuke Okazaki², Alan Mix⁵, Christina Ravelo⁴, Carloz Alvarez-Zarikian³, Mea Cook⁷, Kozo Takahashi², Karla Knudson (1.Kochi University, 2.Kyushu University, 3.IODP Taxas A &M, 4.Univesity of California, Santa Cruze, 5.Oregon State Univesity, 6.University of Exeter, 7.Williams College)

Keywords:Bering Sea, Mid Pleistocene Transition, stratification

CO₂ storage history within the deep ocean at any climatic transitions provides intriguing insights toward understanding the Earth’s Climate system. Several pieces of paleoceanograpic evidence, especially from high latitude, suggest changes in deep water CO₂ storage may play marked roles (or responses) along with the glacial-interglacial pictures. Importantly, deep water CO₂ increases witnessed at Mid Pleistocene Transition (MPT: 0.8-1.2 Ma) elsewhere imply that potential linkage of ocean carbon system toward the global Glacial Interglacial cyclicity. Unlike other high latitudes (e.g., N. Atlantic and the Southern Ocean), evidence from the northern Pacific (and the Bering Sea) has been exclusively limited in associations with poor preservation of calcareous fossils. Here we present species offset corrected for benthic foraminiferal d¹³C and d¹⁸O at a total of seven sites drilled during IODP Exp. 323 in the Bering Sea. Drilled sites are in the Bering Sea (2 sites, 850–2200 m), including those proximal to modern ocean winter ice margin (Bering Slope; 4 sites, 1000–3000m), partially represent regional deep ocean CO₂ storage back to 1.0 Ma. While d¹⁸O at each site present orbital scale age model, d¹³C represents regional (depth-transect) trends. Prior to 1.0 Ma, d¹³C of all sites showed similar values (-1.0 permil). After 1.0 Ma, marked d¹³C drops to -2.0 permil were only witnessed at 3 sites of the Bering Slope. Regarding regional d¹⁸O together, such regional d¹³C can be further interpreted as enhanced deep-water CO₂ rise associated with sea-ice extent over the Bering Slope and Beringia exposure during the glacial period after 1.0 Ma. Together with the coincident of d¹³C drops reported from elsewhere as in the Bering Sea, we hypothesize that ocean stratification due to sea-ice evolution (i.e., reducing ocean CO₂ leakage) after 1.0 Ma has brought strong influence global glacial-interglacial signals.