TY - JOUR
T1 - The influence of hydrology on the dynamics of land-terminating sectors of the Greenland Ice Sheet
AU - Davison, Ben
AU - Sole, Andrew
AU - Livingstone, Stephen
AU - Cowton, Tom
AU - Nienow, Peter
N1 - Funding: The Scottish Alliance for Geoscience, Environment and Society (SAGES) provided financial support for this work in the form of a studentship for BJD.
PY - 2019/2/21
Y1 - 2019/2/21
N2 - Coupling between runoff, hydrology, basal motion and mass loss
(‘hydrology-dynamics’) is a critical component of the Greenland Ice
Sheet system. Despite considerable research effort, the mechanisms by
which runoff influences ice dynamics and the net long-term (decadal and
longer) dynamical effect of variations in the timing and magnitude of
runoff delivery to the bed remain a subject of debate. We synthesise key
research into land-terminating ice sheet hydrology-dynamics, in order
to reconcile several apparent contradictions that have recently arisen
as understanding of the topic has developed. We suggest that meltwater
interaction with subglacial channels, cavities and deforming subglacial
sediment modulates ice flow variability. Increasing surface runoff
supply to the bed induces cavity expansion and sediment deformation,
leading to early-melt season ice flow acceleration. In the ablation
area, drainage of water at times of low runoff from high-pressure
subglacial environments towards more efficient drainage pathways is
thought to result in reductions in water pressure, ice-bed separation
and sediment deformation, causing net slow-down on annual to decadal
time-scales (ice flow self-regulation), despite increasing surface melt.
Further inland, thicker ice, small surface gradients and reduced runoff
supress efficient drainage development, and a small net increase in
both summer and winter ice flow is observed. Predicting ice motion
across land-terminating sectors of the ice sheet over the 21st century
is confounded by inadequate understanding of the processes and feedbacks
between runoff and subglacial motion. However, if runoff supply
increases, we suggest that ice flow in marginal regions will continue to
decrease on annual and longer timescales, principally due to (i)
increasing drainage system efficiency in marginal areas, (ii)
progressive depression of basal water pressure and (iii)
thinning-induced lowering of driving stresses. At higher elevations, we
suggest that minor year-on-year ice flow acceleration will continue and
extend further into the interior where self-regulation mechanisms cannot
operate and if surface-to-bed meltwater connections form. Based on
current understanding, we expect that ice flow deceleration due to the
seasonal development of efficient drainage beneath the land-terminating
margins of the Greenland Ice Sheet will continue to regulate its future
mass loss.
AB - Coupling between runoff, hydrology, basal motion and mass loss
(‘hydrology-dynamics’) is a critical component of the Greenland Ice
Sheet system. Despite considerable research effort, the mechanisms by
which runoff influences ice dynamics and the net long-term (decadal and
longer) dynamical effect of variations in the timing and magnitude of
runoff delivery to the bed remain a subject of debate. We synthesise key
research into land-terminating ice sheet hydrology-dynamics, in order
to reconcile several apparent contradictions that have recently arisen
as understanding of the topic has developed. We suggest that meltwater
interaction with subglacial channels, cavities and deforming subglacial
sediment modulates ice flow variability. Increasing surface runoff
supply to the bed induces cavity expansion and sediment deformation,
leading to early-melt season ice flow acceleration. In the ablation
area, drainage of water at times of low runoff from high-pressure
subglacial environments towards more efficient drainage pathways is
thought to result in reductions in water pressure, ice-bed separation
and sediment deformation, causing net slow-down on annual to decadal
time-scales (ice flow self-regulation), despite increasing surface melt.
Further inland, thicker ice, small surface gradients and reduced runoff
supress efficient drainage development, and a small net increase in
both summer and winter ice flow is observed. Predicting ice motion
across land-terminating sectors of the ice sheet over the 21st century
is confounded by inadequate understanding of the processes and feedbacks
between runoff and subglacial motion. However, if runoff supply
increases, we suggest that ice flow in marginal regions will continue to
decrease on annual and longer timescales, principally due to (i)
increasing drainage system efficiency in marginal areas, (ii)
progressive depression of basal water pressure and (iii)
thinning-induced lowering of driving stresses. At higher elevations, we
suggest that minor year-on-year ice flow acceleration will continue and
extend further into the interior where self-regulation mechanisms cannot
operate and if surface-to-bed meltwater connections form. Based on
current understanding, we expect that ice flow deceleration due to the
seasonal development of efficient drainage beneath the land-terminating
margins of the Greenland Ice Sheet will continue to regulate its future
mass loss.
KW - Subglacial hydrology
KW - Ice dynamics
KW - Land-terminating
KW - Supraglacial lakes
KW - Greenland ice sheet
KW - Glaciers
U2 - 10.3389/feart.2019.00010
DO - 10.3389/feart.2019.00010
M3 - Review article
SN - 1863-4621
VL - 7
JO - Frontiers in Earth Sciences
JF - Frontiers in Earth Sciences
M1 - 10
ER -