DOI: 10.1016/j.epsl.2019.115881
论文题名: The coupled effects of mantle mixing and a water-dependent viscosity on the surface ocean
作者: Chotalia K. ; Cagney N. ; Lithgow-Bertelloni C. ; Brodholt J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 530 语种: 英语
中文关键词: mixing
; parametrised mantle convection
; sea level
; water-dependent viscosity
英文关键词: Antennas
; Degassing
; Sea level
; Viscosity
; Convection model
; Global mean sea levels
; Instantaneous mixing
; Mantle convection
; Mantle rheology
; Mid-ocean ridges
; Simple modeling
; Water in the mantle
; Mixing
; mantle convection
; mid-ocean ridge
; mixing
; Rayleigh number
; sea level
; viscosity
; water content
英文摘要: Water content plays a vital role in determining mantle rheology and thus mantle convection and plate tectonics. Most parameterised convection models predict that Earth initially underwent a period of rapid degassing and heating, followed by a slow and sustained period of regassing and cooling. However, these models assume water is instantaneously mixed and homogeneously distributed into the mantle. This is a limitation because the mixing time for water entering and leaving the mantle is a function of the Rayleigh number which varies dramatically with water content, temperature, and through time. Here we present an adapted parametrised model (Crowley et al., 2011) to include the coupled effects of the time scale of mixing with a water-dependent viscosity. We consider two mixing types: first, where the mixing time is constant throughout the model and second, where mixing time varies as a response to an evolving Rayleigh number. We find that, facilitated by the effects of water content in the melt region at mid-ocean ridges, a constant mixing time can induce long periods of degassing. The inclusion of a variable mixing time dependent on the Rayleigh number acts to limit the period of degassing and also results in more water being stored in the mantle and less at the surface than in both the constant and instantaneous mixing cases. Mixing time cannot be more than ∼2 billion years as large mixing times trap water in the mantle, leaving a dry surface. Even small changes in the surface ocean induced by mixing times on the order of 0.1 Gyrs can cause changes in the global-mean sea level on the order of 10's of metres. These changes in sea level could easily uncover topographic highs in the bathymetry, potentially aiding sub-aerial erosion a process thought to be important in early Earth evolution. Even in this relatively simple model, the inclusion of a mixing time between water entering and leaving the mantle creates a more dynamic water cycle. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164922
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom; School of Engineering and Materials Science, Faculty of Science and Engineering, Queen Mary University of London, Mile End Road, London, E1 4NS, United Kingdom; Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567, United States; Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, 0316, Norway
Recommended Citation:
Chotalia K.,Cagney N.,Lithgow-Bertelloni C.,et al. The coupled effects of mantle mixing and a water-dependent viscosity on the surface ocean[J]. Earth and Planetary Science Letters,2020-01-01,530