Dynamics of ice stream temporal variability: Modes, scales, andhysteresis

Understanding the mechanisms governing temporal variability of ice stream flow remains one of the major barriers to developing accurate models of ice sheet dynamics and iceclimate interactions. Here we analyze a simple model of ice stream hydrology coupled to ice flow dynamics and including drainage...

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Bibliographic Details
Published in:Journal of geophysical research. Earth surface 2013-06, Vol.118 (2), p.925
Main Authors: Robel, A A, DeGiuli, E, Schoof, C, Tziperman, E
Format: Article
Language:English
Subjects:
Cooling
Freezing
Geothermal power
Heating
Hydrology
Ice
Meltwater
Sea level
Stream discharge
Stream flow
Surface temperature
Variability
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Summary:Understanding the mechanisms governing temporal variability of ice stream flow remains one of the major barriers to developing accurate models of ice sheet dynamics and iceclimate interactions. Here we analyze a simple model of ice stream hydrology coupled to ice flow dynamics and including drainage and basal cooling processes. Analytic and numerical results from this model indicate that there are two major modes of ice stream behavior: steadystreaming and bingepurge variability. The steadystreaming mode arises from frictionstabilized subglacial meltwater production, which may also activate and interact with subglacial drainage. The bingepurge mode arises from a sufficiently cold environment sustaining successive cycles of thinninginduced basal cooling and stagnation. Low prescribed temperature at the ice surface and weak geothermal heating typically lead to bingepurge behavior, while warm ice surface temperature and strong geothermal heating will tend to produce steadystreaming behavior. Model results indicate that modern Siple Coast ice streams reside in the bingepurge parameter regime near a subcritical Hopf bifurcation to the steadystreaming mode. Numerical experiments exhibit hysteresis in ice stream variability as the surface temperature is varied by several degrees. Our simple model simulates Heinrich eventlike variability in a hypothetical Hudson Strait ice stream including dynamically determined purge time scale, till freezing and basal cooling during the binge phase. These findings are an improvement on studies of both modern and paleoice stream variability and provide a framework for interpreting complex ice flow models. Key Points We find two modes of ice stream variability: steady-streaming and binge-purge There is hysteresis in ice stream variability Siple Coast ice streams are near an abrupt transition to steady-streaming
ISSN:2169-9003
2169-9011
DOI:10.1002/jgrf.20072