Soft-bed glaciers show a hydrology continuum
Seasonal ice-speed patterns on Icelandic and Norwegian glaciers reveal mixed, not purely channelized or distributed, soft-bed drainage.
Source
Seasonal velocity patterns provide insights for the soft-bed subglacial hydrology continuum
Study at a glance
- Design
- Other — GNSS, till probes, GPR, and Sentinel-1 seasonal velocities on soft-bed outlet glaciers
- N
- N=4 · Four glaciers (Skálafellsjökull, Fjallsjökull, Breiðamerkurjökull, Briksdalsbreen)
- Population
- Soft-bedded Icelandic and Norwegian outlet glaciers
- Outcome
- Seasonal speed-up patterns indicating mixed soft-bed subglacial drainage
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Inspect source passages
Soft-bed glaciers show a hydrology continuum
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
ISMIP6 ice-sheet simulations had about 55% uncertainty tied to subglacial process knowledge.
It has been suggested that this lack of understanding of subglacial process led to a total uncertainty of ~55% between different ice-sheet simulations associated with the Ice Sheet Model Intercomparison for CMIPS (ISMIP6) .
Skálafellsjökull spring speed-up occurs about 17 days after the beginning of spring.
Each year the spring speed-up occurs ~17 days after the beginning of spring (see Methods for derivation of the seasons) and is not related to a specific weather event.
What they did
Authors combined GNSS, in-till wireless probes, GPR, and 12-day Sentinel-1 velocities on Skálafellsjökull, Fjallsjökull, Breiðamerkurjökull, and Briksdalsbreen to relate air temperature, water pressure, and speed-up events.
What they found
Spring speed-ups follow seasonal melt onset (~17 days after spring at Skálafellsjökull) more than single storms. Winter speed-ups track warm days; summer speeds stay high and stable. Diurnal cycles and lake-calving setting differ by glacier, implying a soft-bed hydrology continuum identifiable from Sentinel-1 alone.
The limits
What it doesn't show
Four outlet glaciers do not map all ice sheets. Briksdalsbreen velocities are from nearby Nigardsbreen after retreat. 12-day SAR averages smear daily events, and ISMIP6’s ~55% sliding uncertainty is context, not a new model run.
Key terms
- Soft bed
- Sedimentary till under a glacier whose water pressure controls sliding.
- Effective pressure
- Ice overburden minus basal water pressure; lower values favor faster sliding.
- Spring speed-up
- Seasonal acceleration when meltwater first reaches the bed.
- Distributed drainage
- Sheet-like or linked-cavity water flow, often assumed for soft beds.
- Channelized drainage
- Efficient conduits classically assumed for hard beds in summer.
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Soft-bed subglacial hydrology here is best described as:
Common questions
Is soft-bed drainage always distributed?
No; these glaciers show mixed seasonal behaviors along a continuum.
Can satellites replace in situ sensors?
The authors argue Sentinel-1 seasonal patterns can identify hydrology type.
What triggers winter speed-ups?
High air temperatures (often >5 °C) that generate melt.
Why does summer speed stay high?
Water pressures remain high; velocity variation is only a few percent.
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