A mechanistic analysis of early Eocene latitudinal gradients of isotopes in precipitation

作者：Winnick Matthew J; Caves Jeremy K; Chamberlain C Page

来源：Geophysical Research Letters, 2015, 42(19): 8216-8224.

DOI：10.1002/2015GL064829

• oxygen isotopes
• precipitation
• Eocene climate
• isotope gradients

We use a one-dimensional reactive transport model of isotopes in precipitation (O-18) 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 O-18 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 pCO(2) of 2240 and 4480ppm, we find that meridional isotopic profiles are insensitive to the associated 5 degrees C change in global temperatures due to the relative lack of polar amplification. Finally, we hypothesize that observed negative D 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.

• 出版日期2015-10-16