Abstract

AbstractWe use a one‐dimensional reactive transport model of isotopes in precipitation (δ18O) to investigate the physical mechanisms controlling global meridional isotope profiles under early Eocene hothouse conditions. Simulations of early Eocene precipitation isotopes display reduced meridional gradients relative to the modern climate with the largest increases in δ18O occurring at high latitudes, matching proxy data. These reduced gradients are controlled primarily by polar amplification that increases high‐latitude length scales of specific humidity and match our compilation of proxy‐based reconstructions. Comparing Eocene general circulation model simulations run with pCO2 of 2240 and 4480 ppm, we find that meridional isotopic profiles are insensitive to the associated 5°C change in global temperatures due to the relative lack of polar amplification. Finally, we hypothesize that observed negative δD anomalies in precipitation during peak warming of early Eocene hyperthermal events are the result of a theorized reduction in the strength of midlatitude transient eddies.

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