Variations on a Pathway to an Early Eocene Climate
Variations on a Pathway to an Early Eocene Climate
复制标题
始新世早期气候路径的变化
DOI：
10.1029/2021pa004375
复制
发表时间：
2022
影响因子：
3.5
通讯作者：
Henry M
中科院分区：
文献类型：
--
作者：
Henry M
始新世早期气候的特点是温度比今天高得多，赤道到极地的表面温度梯度比今天更小。综合气候模型在模拟年平均气候方面相当成功。然而，事实证明，对季节变化，特别是陆地上温暖得多的北极冬季进行良好的模拟更加困难。此外，虽然增加温室气体似乎是实现始新世气候所必需的，但尚不清楚是否存在一种独特的因素组合可以导致与所有可用的代理达成一致。在这里，我们使用非常灵活的大气环流模型来检查模拟气候对二氧化碳浓度、陆地表面特性、海洋热传输以及云范围和厚度差异的敏感性。即使没有冰或云量变化，二氧化碳浓度的增加也会导致极地放大的表面温度变化，因为水蒸气水平增加，加上高纬度地区缺乏对流，长波辐射对温度的非线性依赖性放大了陆地冬季的增加。北极陆地上空额外的低云通常会降低夏季气温，并进一步升高冬季气温（二氧化碳水平非常高时除外）。考虑到植被的巨大变化，陆地表面热容量的增加似乎是合理的，同时也降低了北极陆地的季节性。因此，不同的因素组合——高二氧化碳水平、低层云的变化和地表热容量的增加——可以导致在大多数代理数据的代理不确定性范围内进行模拟。
The climate of the early Eocene was characterized by much higher temperatures and a smaller equator‐to‐pole surface temperature gradient than today. Comprehensive climate models have been reasonably successful in simulating that climate in the annual average. However, good simulations of the seasonal variations, and in particular much warmer Arctic winters over land, have proven more difficult. Further, while increased greenhouse gases seems necessary to achieve an Eocene climate, it is unclear whether there is a unique combination of factors that leads to agreement with all available proxies. Here we use a very flexible General Circulation Model to examine the sensitivity of the modeled climate to differences in CO2concentration, land surface properties, ocean heat transport, and cloud extent and thickness. Even in the absence of ice or changes in cloudiness, increasing the CO2concentration leads to a polar‐amplified surface temperature change because of increased water vapor levels combined with the lack of convection at high latitudes, with the nonlinear dependence of longwave radiation on temperature amplifying the increase in winter over land. Additional low clouds over Arctic land generally decrease summer temperatures and further increase winter temperatures (except at very high CO2levels). An increase in the land surface heat capacity, plausible given large changes in vegetation, also decreases the Arctic land seasonality. Thus, different combinations of factors—high CO2levels, changes in low‐level clouds, and an increase in land surface heat capacity—can lead to a simulation within the proxy uncertainty range of the majority of proxy data.
登录
查看更多内容
影响因子：
5.1
作者：
Qun Liu;M. Collins;P. Maher;S. Thomson;G. Vallis
通讯作者：
Qun Liu;M. Collins;P. Maher;S. Thomson;G. Vallis
形成早始新世气候的不同途径
DOI：
--
发表时间：
2021
期刊：
影响因子：
--
作者：
M. Henry;G. Vallis
通讯作者：
G. Vallis
用理想化的潮湿模型解开热带对流层顶层的年循环
影响因子：
4.9
作者：
M. Jucker;E. Gerber
通讯作者：
E. Gerber
影响因子：
4.3
作者：
Henrik Carlson;R. Caballero
通讯作者：
Henrik Carlson;R. Caballero
影响因子：
5.2
作者：
T. Cronin;M. Jansen
通讯作者：
T. Cronin;M. Jansen