Self-consistent generation of single-plume state for Enceladus using non-Newtonian rheology
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Date
2014-03
Publication Type
Journal Article
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yes
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Abstract
The thermal dichotomy of Enceladus suggests an asymmetrical structure in its global heat transfer. So far, most of the models proposed that obtained such a distribution have prescribed an a priori asymmetry, i.e., some anomaly in or below the south polar ice shell. We present here the first set of numerical models of convection that yield a stable single-plume state for Enceladus without prescribed mechanical asymmetry. Using the convection code StagYY in a 2-D spherical annulus geometry, we show that a non-Newtonian ice rheology is sufficient to create a localized, single hot plume surrounded by a conductive ice mantle. We obtain a self-sustained state in which a region of small angular extent has a sufficiently low viscosity to allow subcritical to weak convection to occur due to the stress-dependent part of the rheological law. We find that the single-plume state is very unlikely to remain stable if the rheology is Newtonian, confirming what has been found by previous studies. In a second set of numerical simulations, we also investigate the first-order effect of tidal heating on the stability of the single-plume state. Tidal heating reinforces the stability of the single-plume state if it is generated in the plume itself. Lastly, we show that the likelihood of a stable single-plume state does not depend on the thickness of the ice shell.
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published
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Journal / series
Volume
119 (3)
Pages / Article No.
416 - 439
Publisher
American Geophysical Union
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Subject
Enceladus; Convection; Non-Newtonian; Single-plume; Tidal heating; Subcritical
Organisational unit
03698 - Tackley, Paul / Tackley, Paul