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arXiv 1803.10751astro-ph.EPphysics.ao-ph
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在一个耦合的大气-海洋模式中在高湿度下稳定的赤道冰带

Stable equatorial ice belts at high obliquity in a coupled atmosphere-ocean model

Cevahir Kilic, Frank Lunkeit, Christoph C. Raible, Thomas F. Stocker

摘要:

利用一个水行星结构的动态大气-海洋-海冰气候模式,实现了在一系列恒星辐照度下,高密度下的各种气候状态。三个稳定的气候状态得到不同的海冰覆盖的程度。对于低辐照度值,该模型模拟了具有常年全球海冰覆盖的Cryoplanet。通过增加恒星辐照度,转变发生在一个常年赤道海冰带的无盖冰冻行星上,最终转变为一个没有冰的水行星。使用模拟器模型,我们发现,无帽Cryoplanet是一个强大的稳定状态的范围内的辐照度和高的CO2和对比早期的结果,高CO2的气候状态与赤道冰带可能是不可持续的或无法实现的。当赤道海洋热通量增强时,由于赤道海冰的融化,允许一个稳定的无盖冰冻行星的参数范围减小。当赤道海洋热通量超过一个临界阈值时,常年赤道冰带消失。因此,一个强大的海洋环流可能会使它不稳定。我们的研究结果表明,常年赤道冰层覆盖是一个可行的气候状态的高湿度系外行星。然而,由于多重平衡,这种状态只能从更多的冰川条件下达到,而不是从较少的冰川条件。

英文摘要:

Various climate states at high obliquity are realized for a range of stellar irradiance using a dynamical atmosphere-ocean-sea ice climate model in an Aquaplanet configuration. Three stable climate states are obtained that differ in the extent of the sea ice cover. For low values of irradiance the model simulates a Cryoplanet that has a perennial global sea ice cover. By increasing stellar irradiance, transitions occur to an Uncapped Cryoplanet with a perennial equatorial sea ice belt, and eventually to an Aquaplanet with no ice. Using an emulator model we find that the Uncapped Cryoplanet is a robust stable state for a range of irradiance and high obliquities and contrast earlier results that high-obliquity climate states with an equatorial ice belt may be unsustainable or unachievable. When the meridional ocean heat flux is strengthened, the parameter range permitting a stable Uncapped Cryoplanet decreases due to melting of equatorial sea ice. Beyond a critical threshold of meridional ocean heat flux, the perennial equatorial ice belt disappears. Therefore, a vigorous ocean circulation may render it unstable. Our results suggest that perennial equatorial ice cover is a viable climate state of a high-obliquity exoplanet. However, due to multiple equilibria, this state is only reached from more glaciated conditions, and not from less glaciated conditions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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