2024 to 2025 stake height change

[jasonebox]

using the following codes, I can remove offsets and obtain ice ablation results

JAR_O
From maintenance sheets…2024 08 19 438.5 cm, 2025 08 20 318 cm Difference: 438.5-318 = 120.5 … makes sense
From daily stake SR50 data: no result as SR50 was out
SWC_O
From maintenance sheets…2024 08 20 182 cm, 2025 08 20 437 cm Difference: 437-182 = 255 … seems too high, subtracting 2 m makes more sense, i.e. 55 cm ablation
From daily stake SR50 data: end of melt season (EOMS) 2024 to EOMS 2025 = 0.565 m
average of the two: 0.558 m ice ablation

                if site=='JAR':
                    df.loc['2024-08-20':, 'temp'] += 2.451
                    df.loc['2023-09-19':, 'temp'] -= 0.9852

                    print(df.loc['2023-08-10':'2023-11-10', 'temp'].max())
                    print(df.loc['2024-08-1':'2024-11-10', 'temp'].max())
                if site=='SWC':
                    df.loc['2024-08-27', 'temp'] =np.nan
                    df.loc['2025-08-20':, 'temp'] += 2.01
                    df.loc['2025-08-20':, 'temp'] =np.nan
                    df.loc['2024-08-24', 'temp']
                    # df.loc['2023-09-19':, 'temp'] -= 0.9852

                    print(df.loc['2024-08-10':'2024-08-30', 'temp'].max())
                    print(df.loc['2025-08-1':'2025-08-25', 'temp'].max())```

[BaptisteVandecrux]

Hi Jason,

Thanks for reporting those values.

I have updated the surface height adjustment.
The stitched surface height (in brown in the middle panel) should now look like:

Yearly ice ablation:
2022: -0.39 m (starting in August)
2023: -0.88 m
2024: -0.57 m
2025: -0.75 m (set manually due to data gap)
Because of the failure of SR50 on stake and PTA the ice ablation for 2025 is manually defined. Should it really be 120cm like you report? It is very high compared to the previous years. Note that we anyways ask users not to trust surface height change over data gaps.

Here is how SWC_O should look like once the new adjustments have been processed:

Yearly ice ablation:
2022: -0.28 m (starting in August)
2023: -0.52 m
2024: -0.05 m
2025: -0.73 m

[jasonebox]

I've dug into field notes and photos from 2024 and 2025. The following is about JAR and it's not as conclusive as I'd like...

I now see that in maintenance sheets, at the 2024 visit, we did not record the height of the SR-50 stake after maintenance. From photos, I estimate the SR-50 stake top 2024 08 19 at 174 cm. ~ a year later, on 2025 08 20, the carbon stake height was observed to be 318 cm, so the difference: 318 - 174 suggests 144 cm ice ablation...

Now, from carbon stakes installed on a triangle ~ 600 m N, E and W of JAR_O for our GNSS survey, we made stake height measurements on the same dates in 2024 and 2025. From these, we get ablation rates of:

JAR 25N: 221 cm
JAR 25W 268 ablation
JAR 25E: 100 cm ablation

Wow, these numbers are all over the place! Assuming the values are OK, the 4 stake-based results average (221,268,100,144) 183 cm

From your graphic above, measuring ablation from end of melt season (EOMS) 2024 to EOMS 2025, looks like ca. 80 cm ice ablation.

My sense is that 2025 was a stronger melt year than the previous two melt seasons.

Above you write "2025: -0.05 m". Is that meant to be EOMS 2025 minus EOMS 2024?

Jason

ps. there are still the heights of the continuous GPS sensors from 2024 and 2025 to compare.

[BaptisteVandecrux]

Apologies, there was a problem with my calculation. AWS surface height indicate:

JAR_O

Summer ablation:
2022: -0.39 m (starting in August)
2023: -0.88 m
2024: -0.57 m
2025: -0.75 m (set manually due to data gap)

SWC_O

Summer ablation:
2022: -0.28 m (starting in August)
2023: -0.52 m
2024: -0.05 m
2025: -0.73 m