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Titel |
Cyclic behaviour on millennial time scale due to creep instabilities in western Dronning Maud Land, Antarctica |
VerfasserIn |
Thomas Kleiner, Angelika Humbert |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250080808
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Zusammenfassung |
At the base of a thick ice sheet the temperature locally reaches the pressure melting point and
melting generates a thin subglacial water layer. The basal water lubricates the base and thus
enhances the sliding of the ice sheet. As a consequence of sliding, the heat source of internal
strain heating decreases and the basal ice cools down over time. When frictional heat and heat
advection do not counterbalance this, the ice will become frozen to the bedrock again.
In addition, strain heating within a temperate ice layer generates a liquid water
fraction in the ice, leading to a softer material and enhanced deformation. If the
horizontal or vertical advection of cold ice to the base is weak, this positive feedback
will lead to a local creep instability. The effect of basal water is thus twofold: it
affects the sliding, as well as the rheology and via both ways the ice dynamics.
Subglacial water is therefore a crucial component in the dynamic evolution of ice
sheets.
We present numerical simulations of the present day ice flow using the three-dimensional
thermo-coupled full- Stokes model TIM - FD3 on a 2.5 km horizontal grid in the area
of the western Dronning Maud Land, Antarctica, including the three ice streams
Stancomb-Wills, Veststraumen and Plogbreen and the adjacent Brunt and Riiser- Larsen ice
shelves. Three different flux routing algorithms for the subglacial meltwater and a modified
Weertman-type sliding relation were implemented in the model to account for higher sliding
velocities under wet basal conditions.
Subsequent to spin-up simulations different sliding simulations considering wet and dry
basal conditions were performed. The simulations show a cyclic behaviour on millennial time
scale at distinct locations in the model domain. We estimate the distribution of subglacial
water based on different flux routing methods and the effect on the ice flow and the basal
thermal regime. We further present our analysis of the involved feedback mechanism
between ice flow, temperature and rheology, that are related to the simulated cyclic
behaviour. |
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