气候变化领域集成服务门户(CCPortal): The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5

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DOI	10.5194/cp-16-2573-2020
	The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5
	Baatsen M.; Von Der Heydt A.S.; Huber M.; Kliphuis M.A.; Bijl P.K.; Sluijs A.; Dijkstra H.A.
发表日期	2020
ISSN	1814-9324
起始页码	17
结束页码	27
卷号	16 期号:6
英文摘要	The early and late Eocene have both been the subject of many modelling studies, but few have focused on the middle Eocene. The latter still holds many challenges for climate modellers but is also key to understanding the events leading towards the conditions needed for Antarctic glaciation at the Eocene-Oligocene transition. Here, we present the results of CMIP5-like coupled climate simulations using the Community Earth System Model (CESM) version 1. Using a new detailed 38 Ma geography reconstruction and higher model resolution compared to most previous modelling studies and sufficiently long equilibration times, these simulations will help to further understand the middle to late Eocene climate. At realistic levels of atmospheric greenhouse gases, the model is able to show overall good agreement with proxy records and capture the important aspects of a warm greenhouse climate during the Eocene. With a quadrupling of pre-industrial concentrations of both CO2 and CH4 (i.e. 1120 ppm and ∼2700 ppb, respectively, or 4 × PIC; pre-industrial carbon), sea surface temperatures correspond well to the available late middle Eocene (42-38 Ma; ∼ Bartonian) proxies. Being generally cooler, the simulated climate under 2 × PIC forcing is a good analogue for that of the late Eocene (38-34 Ma; ∼ Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are in agreement with the available information. Our simulated middle to late Eocene climate has a reduced Equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation, and ice account for a global average 5-7 °C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. This helps to explain Eocene warmth in general, without the need for greenhouse gas levels much higher than indicated by proxy estimates (i.e. ∼500-1200 ppm CO2) or low-latitude regions becoming unreasonably warm. High-latitude warmth supports the idea of mostly ice-free polar regions, even at 2 × PIC, with Antarctica experiencing particularly warm summers. An overall wet climate is seen in the simulated Eocene climate, which has a strongly monsoonal character. Equilibrium climate sensitivity is reduced (0.62 °C W-1 m2; 3.21 °C warming between 38 Ma 2 × PIC and 4 × PIC) compared to that of the present-day climate (0.80 °C W-1 m2; 3.17 °C per CO2 doubling). While the actual warming is similar, we see mainly a higher radiative forcing from the second PIC doubling. A more detailed analysis of energy fluxes shows that the regional radiative balance is mainly responsible for sustaining a low meridional temperature gradient in the Eocene climate, as well as the polar amplification seen towards even warmer conditions. These model results may be useful to reconsider the drivers of Eocene warmth and the Eocene-Oligocene transition (EOT) but can also be a base for more detailed comparisons to future proxy estimates. © 2020 Royal Society of Chemistry. All rights reserved.
来源期刊	Climate of the Past
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/183624
作者单位	Department of Physics, Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, Utrecht, 3584CC, Netherlands; Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 610 Purdue Mall, West Lafayette, IN 47906, United States; Department of Earth Sciences, Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Utrecht University, Princetonlaan 8a, Utrecht, 3584CB, Netherlands
推荐引用方式 GB/T 7714	Baatsen M.,Von Der Heydt A.S.,Huber M.,et al. The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5[J],2020,16(6).
APA	Baatsen M..,Von Der Heydt A.S..,Huber M..,Kliphuis M.A..,Bijl P.K..,...&Dijkstra H.A..(2020).The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5.Climate of the Past,16(6).
MLA	Baatsen M.,et al."The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5".Climate of the Past 16.6(2020).