the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Feb 2026
A low-cost ice melt monitoring system using wind-induced motion of mass-balance stakes
Abstract. Surface ablation measurements of glaciers are critical for understanding mass change over time. Mass-balance stakes are commonly used for localized measurements, with the exposed length typically measured manually at infrequent intervals. This paper presents the design and validation of new instrumentation that automates mass-balance stake readings, thus enabling continuous measurements with high temporal resolution. The instrumentation comprises readout electronics that are mounted on mass-balance stakes to measure wind-induced vibrations. The stake vibrational frequency depends sensitively on the exposed length, and changes in the measured frequency therefore probe glacier surface melt and accumulation. Initial instrumentation field tests conducted at Color Lake on Umingmat Nunaat (Axel Heiberg Island), Nunavut, demonstrate centimeter-level precision on length measurements. The instrumentation can be attached to existing mass-balance stakes and is low-cost (~ $50 USD) in comparison to many other systems that perform automated surface ablation measurements. The accessibility of this instrumentation opens new possibilities for localized, high temporal resolution measurements of glacier surface activity at any locations where mass balance stakes are deployed.
Status: open (until 28 Mar 2026)
- RC1: 'Comment on egusphere-2026-428', Anonymous Referee #1, 15 Mar 2026 reply
Data sets
May 2025 data from Color Lake and lab data Felix St-Amour and Laura Thomson https://doi.org/10.5281/zenodo.18292185
Model code and software
Code to analyze BRACHI data Felix St-Amour https://doi.org/10.5281/zenodo.18292185
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- 1
This paper introduces a new approach for continuous measurement of glacier ice melt (surface ablation). The concept is to use an accelerometer to measure the vibrational frequencies of a mass balance stake hourly to determine the amount of the stake that is exposed, which is related to surface ablation. To the best of my knowledge this concept is entirely novel and, since the cost of the instrument is low, this could be an excellent addition to the glaciological toolkit. While this shows a lot of promise, it is not quite ready for prime time. The paper shows clearly how this technology could work conceptually but the testing is not thorough and reveals issues that need to be tackled. A final test on a glacier is a real must, of course. It is good to know that this is currently in progress, but there are details yet to work through.
My recommendation would be to either A) wait to publish until there are more answers to the questions raised below (i.e. manuscript rejection/withdrawal) or B) rescope and reframe this paper to be more of a record of a proof of concept. If the authors chose the latter, the manuscript could be publishable after (1) explaining the limitations of this instrument for the goal of mass balance measurement, (2) redoing some of the tests, explaining the challenges that lie ahead for (3) field testing and (4) operational use. This would serve to anchor your contribution in the literature and provide a roadmap for the second paper.
Here are considerations and questions relating to points 1-4 above:
Lab conditions should ideal conditions when you are testing your technology. If there are issues with this setup, it is hard to interpret field tests in less than ideal conditions. If the clamping was not done correctly, it would be best to redo your work so you can be sure of the data. Likewise, if you don’t have a surface to test the sonic ranger against, then get a sheet of plywood and a bracket to create one. Is there interference with the pole itself?
Testing should be first done thoroughly in the lab. Using a lake to test is an excellent idea. It doesn’t need to be in the Arctic though. It could be near Montreal. Another option is to create a mound of ice with water. That ice can ablate over time during a test and this could be monitored closely. Close observation would be helpful before testing on a glacier.
It would be good to test both the accelerometer and sonic ranger against manual measurements. If your sonic ranger model is not good enough for a comparison, add one that is, at least for the testing. Other instruments and a timelapse camera would be great as well.
Using more than one stake at each length for field and lab testing is essential. This can be used to estimate error.
Temperature dependence should be worked out. Why is this happening? The effect needs to be isolated and removed or put in the error term.
If there is no wind, there will be no motion to measure. How often do you anticipate there not being enough wind to get a measurement of F1 and F2? Or at least can you give some indication of the wind required to induce these frequencies?
Testing different brands of the same stake (pipe) will show how sensitive the method is to differences in manufacturing. What happens if the stake is slightly bent or damaged? Will that invalidate the measurement? At what point?
How easy is it to use a different kind of stake? Can users easily recalibrate to make use of steel, wood or plastic stakes? Glaciologists will need to know this to adopt the method.
What happens when it snows? Loose snow won’t constrain the stake. Will dense snow constrain the stake vibration? At what point? Is there a way to use the sonic ranger to detect snow and account for it?
What happens when the ice surface around the stake melts a little water-filled hole such that the stake is held firmly ~15 cm below the general ice surface?
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Specific comments:
Title: I think surface ablation is better than ice melt in the title
Abstract
Surface ablation measurements of glaciers are critical for understanding mass change over --> Surface ablation measurements are critical for understanding glacier mass change over
depends sensitively on the exposed length, --> depends sensitively on their exposed length,
Color Lake --> Colour Lake (here and elsewhere in the manuscript – proper name with Canadian spelling)
surface activity at any locations --> surface activity at any location
1. Introduction
Hulth (2010) presents a draw-wire method, although the measurement is sensitive to only surface lowering and not accumulation --- I think your method and many of the others presented also cannot measure accumulation at least directly (since for mass accumulation, snow density needs to be known)
representing annual or seasonal summer and winter balances, respectively --> representing annual or seasonal (summer and winter) balances, respectively
2 BRACHIOSAURUS design
, and a depth sensor (Figure 1 (b)). This sensor measure range. It is a sonic ranger and it measures distance. There is no quantity ‘depth’ being examined in this paper. I recommend you replace depth with range or distance.
2.2 Depth [Range] sensor
Sonic range varies according to temperature (which affects the speed of sound). Please explain how this is corrected for.
The sonic pulse will spread out with distance from the sensor. What is the angle that describes the cone of ensonification? How do you avoid having the pole interfere with this measurement?
2.5 Circuit board...
sensor ‘eyes’ -> sensor transducers
3 Vibrational frequency
Equation explanation of symbols – please include the units of measure here as well.
The mass of BRACHI (assumed here to be a point mass at the end of the beam)
Fig 2 caption – make clear that numerical solution is for extended mass and analytic is for point mass
4. Data acquisition...
10 equal length chunks of 12 s each
below the noise floor – can you explain what the noise floor is in this case and why you would not just eliminate data that is below it? I think it is a matter of rewording the sentence to be clearer.
Future measurements will save and process the motion of all axes separately without squaring. - This needs to be explained (why) and moved to a better place (Future development section?)
Local maxima that lie above the noise floor – define the noise floor.
Finding a candidate F1, determined by ...highest amplitude within a frequency range of 0 to 2F1 -- this seems rather circular logically. You need F1 to look for F1? !
By numerically propagating the errors from F1 and F2 – how do you determine the errors for F1 and F2? How are they propagated? In quadrature? Other? What happens if F1 or F2 can’t be found?
Fig 3 – label the peaks adjacent to F2 as F2-F1 and F2+F1
5 Lab measurements
2.7 g/cm^3
radii were respectively measured --> measured respectively
Non-rigidity in the clamping point – please explain your set up here. Ideally you would redo it properly.
Analysis of higher-order modes, if present --- how often are they present? Under what conditions?
Estimated precision of 0.25 cm – explain how you derive this? Is it variation in ice surface? Parallax error? Other?
Although the depth sensor was tested qualitatively in the lab... I think you can do better!
6.1 BRACHI comparison against ...
was below freezing and at a local minimum – what do you mean by ‘at a local minimum’?
Surrounding the stake is solid --> replace with not actively melting
failed to detect ... degraded performance at low temperatures ... close to... operational limits – the temperature range is down to -20C but the temperature was not always close to this. Please look for another reason.
The BRACHI -derived lengths – there are 2 sensors to detect lengths. Please be specific
Temperature-dependent systematic effects – Yes, agreed you have some digging to do to explain how your system is impacted by temperature.
How are you measuring temperature? Can you measure actual ambient air temperature?
Figure 6 –
It would be good to know if you measured the length of the stake during this time. Maybe there was ablation?
How are you computing the error bars in this graph?
7 Conclusions
I think you can only characterize your field tests as partly successful
References:
axel heiberg island canadian high arctic – capitaliztion