Metalimnion Thickness

Locate one contiguous sampled metalimnion using a caller absolute-gradient threshold; disjoint layers are ambiguous and are not merged into a false single thickness.

Description

The metalimnion is a transition layer identified from strong vertical temperature gradients.

The metalimnion is a transition layer identified from strong vertical temperature gradients. A sampled-gradient threshold defines its boundaries at observed depths.^[1]

The tool returns topMetalimnionDepthM, bottomMetalimnionDepthM, metalimnionThicknessM. The computation uses supplied observations and parameters rather than acquiring measurements.

When to use Metalimnion Thickness

Use this for the following task: Locate one contiguous sampled metalimnion using a caller absolute-gradient threshold; disjoint layers are ambiguous and are not merged into a false single thickness. Prepare observations and calibration parameters on the same unit and reporting basis.

How to use Metalimnion Thickness and understand its results

Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
Enter depthsM, temperaturesC, minimumThermalGradientCPerM according to the field table, then run the tool.
Read topMetalimnionDepthM, bottomMetalimnionDepthM, metalimnionThicknessM. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
Review the supplied assumptions and calibration before comparing or reporting the result.

Input field	Meaning	Value type and bounds	Requirement
depthsM	Depths m	list of number	Required
temperaturesC	Temperatures c	list of number	Required
minimumThermalGradientCPerM	Minimum thermal gradient c per m	number	Required

Supply aligned temperatures and increasing nonnegative depths, plus a positive threshold. Find the first and last selected intervals and require every intervening interval also selected.

select interval when abs(ΔT/Δz)≥minimumGradient; thickness=bottomDepth−topDepth

The symbols and boundary conditions refer to the supplied fields and the implementation described above.

Output field	Meaning	Value type
topMetalimnionDepthM	Top metalimnion depth m	number
bottomMetalimnionDepthM	Bottom metalimnion depth m	number
metalimnionThicknessM	Metalimnion thickness m	number

json

{
  "input": {
    "depthsM": [
      0,
      5,
      10,
      15
    ],
    "temperaturesC": [
      20,
      19,
      9,
      8
    ],
    "minimumThermalGradientCPerM": 1
  },
  "output": {
    "topMetalimnionDepthM": 5,
    "bottomMetalimnionDepthM": 10,
    "metalimnionThicknessM": 5
  }
}

Limitations and assumptions

No selected interval or disjoint selected layers is rejected. The threshold is caller chosen, and boundaries are sample depths rather than continuous fitted interfaces.

Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.

Alternative or Complementary methods

Choose Thermocline Depth Max Gradient when you need its operation: Identify a unique maximum absolute interval temperature gradient, reporting interval center rather than claiming sub-sample thermocline precision. Choose Epilimnion Hypolimnion Volume Split for the complementary operation: Integrate a supplied piecewise-linear area-depth curve across thermal-layer boundaries including split contour intervals; geometry is supplied, not reconstructed from map coordinates.

Background reference: Lake Physics Tools: rLakeAnalyzer reference manual.

References

Lake Physics Tools: rLakeAnalyzer reference manual — Winslow, Read and colleagues; GLEON

Similar or alternative tools

Thermocline Depth Max Gradient
Identify a unique maximum absolute interval temperature gradient, reporting interval center rather than claiming sub-sample thermocline precision.
Epilimnion Hypolimnion Volume Split
Integrate a supplied piecewise-linear area-depth curve across thermal-layer boundaries including split contour intervals; geometry is supplied, not reconstructed from map coordinates.