Seawater oxygen isotopes fingerprint of Atlantic Meridional Overturning Circulation patterns in mid-Miocene simulations

Résumé fourni par la source

Atlantic Meridional Overturning Circulation (AMOC) pattern and strength have been shown to be highly sensitive to prescribed boundary conditions across mid-Miocene simulations. Among previously published mid-Miocene studies the intensity of simulated AMOC varies from weak to vigorous, including within single model ensemble. Shifts in AMOC are known to affect, among others, North Atlantic sea surface temperatures and atmospheric circulation and hydroclimate in the tropics. Yet, the assessment of how those changes would affect the oxygen isotope ratio of seawater remains limited; so is the potential implication for model-data comparison and the understanding of Miocene climate evolution. In this contribution we used mid-Miocene simulations with the water isotopes enabled Community Earth System Model (iCESM1.2) to investigate the relation between AMOC, regional ocean and atmosphere circulations and isotopic composition of seawater. Our set of simulations includes sensitivity tests to AMOC strength and atmospheric concentration of CO2. Our analysis shows that different AMOC patterns generate strong changes in both seasonality and upper ocean structure that are fingerprinted in the isotopic signal of the Northern Hemisphere and the tropical band. Our simulations offer mechanistic understanding for changes depicted in isotopic records from the tropical basins during and after the Mid-Miocene Climate Transition (14.6-13.9Ma).

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