Weertman Basal Sliding Law
Evaluate a supplied Weertman-type power sliding law C·sign(tau)|tau|^p/N^q; coefficient is unit-specific and zero/negative effective pressures lie outside the model.
Description
Basal sliding relates ice motion over its bed to basal stress and water-modified effective pressure.
Basal sliding relates ice motion over its bed to basal stress and water-modified effective pressure. A power law requires a coefficient calibrated to its chosen units.1
Evaluate a supplied Weertman-type power sliding law C·sign(tau)|tau|^p/N^q; coefficient is unit-specific and zero/negative effective pressures lie outside the model.
When to use Weertman Basal Sliding Law
Use this for the following task: Evaluate a supplied Weertman-type power sliding law C·sign(tau)|tau|^p/N^q; coefficient is unit-specific and zero/negative effective pressures lie outside the model.
Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
How to use Weertman Basal Sliding Law and understand its results
- Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
- Enter signedBasalShearStressesPa, effectivePressuresPa, slidingCoefficient, stressExponent, pressureExponent using the field table, then run the tool.
- Read signedSlidingVelocitiesMPerYear. Interpret flags, units, ordering and placeholder values using the rules below.
- Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| signedBasalShearStressesPa | Signed basal shear stresses pa | list of number; each entry: number | Required |
| effectivePressuresPa | Effective pressures pa | list of number; each entry: number | Required |
| slidingCoefficient | Sliding coefficient | number | Required |
| stressExponent | Stress exponent | number | Required |
| pressureExponent | Pressure exponent | number | Required |
Pair signed stresses with strictly positive pressures. Require C and p positive and q nonnegative; preserve the stress sign and return velocities in meters per year.2
u = C sign(τ)|τ|^p / N^q This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| signedSlidingVelocitiesMPerYear | Signed sliding velocities m per year | list of number |
{
"input": {
"signedBasalShearStressesPa": [
-2,
0,
2
],
"effectivePressuresPa": [
4,
4,
4
],
"slidingCoefficient": 3,
"stressExponent": 2,
"pressureExponent": 1
},
"output": {
"signedSlidingVelocitiesMPerYear": [
-3,
0,
3
]
}
}Limitations and assumptions
The law is supplied rather than fitted. Zero/negative effective pressure is outside this model; no thermal or hydrological switching is inferred.
Constants and empirical coefficients are supplied rather than calibrated. Check units and observational applicability before interpreting the model. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.
Alternative or Complementary methods
Choose Glen Flow Law Strain Rate for this operation: Evaluate signed scalar Glen shear strain rate A·E·sign(tau)|tau|^n; A units follow n, and shear tensor strain rate differs by a factor two from engineering shear rate. For a complementary task, use Effective Pressure Nye for this operation: Calculate signed ice-overburden minus subglacial water pressure and flag pressure above overburden; negative effective pressure is not clamped or interpreted as stable contact.
Further background: Basal strength and sliding laws.
References
-
Weertman Basal Sliding Law — tool.io
Similar or alternative tools
- Glen Flow Law Strain Rate
Evaluate signed scalar Glen shear strain rate A·E·sign(tau)|tau|^n; A units follow n, and shear tensor strain rate differs by a factor two from engineering shear rate.
- Effective Pressure Nye
Calculate signed ice-overburden minus subglacial water pressure and flag pressure above overburden; negative effective pressure is not clamped or interpreted as stable contact.