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Land-terminating GrIS (Tedstone et al 2015 (Spatial scale (~ 800 km2 area)…
Land-terminating GrIS
Limitation Leverett Study
Lack of
Long-term observations
Over large areas (limited spatial coverage)
Enter:
Tedstone 2015 study
Tedstone et al 2015
Broader scale study
Spatial scale
~ 800 km2 area
Time scale
1985 - 2014
Used satellite imagery (Landsat)
to derive annual ice velocities
Tedstone Finding 1
84% study area
slowed
~ 12% decrease in ice motion
[2007 - 2014] vs [1985 - 1993]
Implications
Regional trends agree with Leverett study
i.e.
Not anomalous behaviour
@ Leverett
Systematic ↓ ice velocity
→ related to enhanced melt season
Why ?
More efficient drainage system
extends further into ice sheet
Key conclusions Tedstone
50% rise in meltwater production
→
has NOT led to speedup
along land-terminating margin
Instead: Ice has
slowed
on average by ~12%
Slow down
SLOWDOWN = marked
Found 2 statistically different periods of ice motion
1985 - 2001 vs 2002 - 2014
Slowdown cause proposed
Likely driven by
long term ↓ subglacial water pressure
→ resulting from
more extensive efficient subglacial drainage
(upglacier)
Land- terminating conclusions
Ice motion evolves
in
response to subglacial hydrology ∆
forced by supraglacial melt ∆
No evidence
for runaway dynamic response
in a warming climate
Land-terminating annual
slowdown
suggested