Flux Gate Discharge

Integrate signed normal ice flux over supplied gate strips with depth-mean/surface velocity calibration; widths are physical section measurements, not geodesy coordinates.

Description

Flux gates measure how much ice crosses a section.

Flux gates measure how much ice crosses a section. Thickness, width, velocity direction and depth-mean calibration each affect the signed discharge.^[1]

Integrate signed normal ice flux over supplied gate strips with depth-mean/surface velocity calibration; widths are physical section measurements, not geodesy coordinates.

When to use Flux Gate Discharge

Use this for the following task: Integrate signed normal ice flux over supplied gate strips with depth-mean/surface velocity calibration; widths are physical section measurements, not geodesy coordinates.

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 Flux Gate Discharge 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 gateWidthsM, iceThicknessesM, surfaceSpeedsMPerYear, anglesFromGateNormalDegrees, depthMeanSurfaceVelocityRatios using the field table, then run the tool.
Read segmentIceFluxesM3PerYear, totalIceFluxM3PerYear. 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
gateWidthsM	Gate widths m	list of number; each entry: number	Required
iceThicknessesM	Ice thicknesses m	list of number; each entry: number	Required
surfaceSpeedsMPerYear	Surface speeds m per year	list of number; each entry: number	Required
anglesFromGateNormalDegrees	Angles from gate normal degrees	list of number; each entry: number	Required
depthMeanSurfaceVelocityRatios	Depth mean surface velocity ratios	list of number; each entry: number	Required

Pair all strip vectors, requiring positive widths and nonnegative thicknesses, speeds and ratios. Convert angles from degrees and sum signed normal fluxes.^[2]

Qsegment = width × H × surfaceSpeed × velocityRatio × cos(angleDegrees)

This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.

Output field	Meaning	Value type
segmentIceFluxesM3PerYear	Segment ice fluxes m3 per year	list of number
totalIceFluxM3PerYear	Total ice flux m3 per year	number

json

{
  "input": {
    "gateWidthsM": [
      10,
      20
    ],
    "iceThicknessesM": [
      100,
      50
    ],
    "surfaceSpeedsMPerYear": [
      20,
      10
    ],
    "anglesFromGateNormalDegrees": [
      0,
      60
    ],
    "depthMeanSurfaceVelocityRatios": [
      0.8,
      1
    ]
  },
  "output": {
    "segmentIceFluxesM3PerYear": [
      16000,
      5000.000000000001
    ],
    "totalIceFluxM3PerYear": 21000
  }
}

Limitations and assumptions

Widths are physical section measurements. Surface-to-mean ratios are supplied, and angles can produce inward negative flux.

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 Gate Velocity Balance Flux for this operation: Invert integrated upstream water-equivalent net balance to steady depth-mean gate velocity; negative balance demands inward flux under this ideal storage-free budget. For a complementary task, use Parabolic Channel Discharge for this operation: Analytically integrate local slab Glen flux over a parabolic thickness section plus uniform sliding; excludes lateral stress coupling and uses stress-gradient units Pa/m.

Further background: Glacier accumulation, ablation and mass balance.

References

Glacier accumulation, ablation and mass balance — USGS
Flux Gate Discharge — tool.io

Similar or alternative tools

Gate Velocity Balance Flux
Invert integrated upstream water-equivalent net balance to steady depth-mean gate velocity; negative balance demands inward flux under this ideal storage-free budget.
Parabolic Channel Discharge
Analytically integrate local slab Glen flux over a parabolic thickness section plus uniform sliding; excludes lateral stress coupling and uses stress-gradient units Pa/m.