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GrIS ∆ 2 (Alpine System Iken & Bindschadler 1986 (Basal water…
GrIS ∆ 2
Motivation
Biggest error SLR estimates
Lack of understanding of
drivers
of likely dynamic change
What contribution will GrIS dynamic ∆ make to sealevel rise ?
Driver Observed Dynamic ∆
Is the cause
Atmospheric ? (Zwally, 2002)
Oceanic ? (Holland et al 2008)
Big GrIS Study
Investigate
role of atmos forcing
on dynamic stability
of Greenland's outlet glaciers
Field-based
To get @
processes
causing dynamic ∆
= Difficult to do from satellite obvs alone
Aim
Does ↑ surface melt lead to ↑ ice flow (acceleration) ?
Research Q/ Hypotheses
Will IS margin/interior
accelerate
with climate warming ?
Test Zwally hypothesis
↑ Melt accessing bed
∴ Overpressurises/lubricates bed
→ enhanced basal sliding (acceleration)
Possible positive feedback
Accelerated flow → quick mass transfer
(from high to low elevations)
∴ Greater potential to melt @ lower elevations ?
Thus enhancing basal sliding...
Melt Enhancement Ice Velocity
Observed @ polythermal/temperate glaciers
smaller alpine glaciers
e.g. Bingham 2003 - summer enhanced vs winter
Zwally Hypothesis
Suggested surface melt & dynamics may also be related on GrIS
Alpine System
Iken & Bindschadler 1986
Basal water pressure ↑ drives ice velocity ↑
Closer get to floating ice, lower the friction
∴ Enhanced basal sliding
→ Further melting = positive feedback
Subglacial drainage system
Affects basal water pressure ∴ ice motion
Theoretically when in steady-state
Efficient channelised
Melt Q ↑ causes water pressure ↓
Inefficient distributed
Melt Q ↑ causes ↑ basal water pressure
Land terminating part GrIS
Hydrology vs flow velocity ∆
Uncertain if relation on ice sheets resembles that in alpine glaciers
Thus= focus of much study