2024 melt season buoy data

[uniquorn]

With the first signs of bottom melt on SIMB3 2024H it's time to start the 2024 melt season buoy data thread. As always, best efforts to get the analysis here correct but most of it will be done 'quickly' in near real time using raw data and it's highly likely that no one else is checking it.

There are a lot more SIMB3's this year so feel free to adopt one and keep an eye on it.

Bottom melt appears to have started in the western Beaufort Sea at 74.56 N, 155.4 EW!, the location of ice mass balance buoy 651330:

Snap! 2024H has begun bottom melt nearby a year later at 74.51, -157.06

Ice TypeFYI
FYI with no snow. Appears to be full-winter ice, and is surprisingly thin. Especially with no snow cover.

Snow depth has increased since deployment to ~8cm, air temps peaked at 1.625C turning negative at low sun, buoy temps peaked higher at 8.56C so probably sunny. First image optimised to show recent ice temps at -1C to -5C
Comparison of (mislabelled?) 2021#9 and 2024H apr15 to may 2023 and 2024

Could be due to ocean temperature as that location is where warm jets from the Barrow Canyon may drift and there is also a trough near that area where warmer pacific water may be sinking from the Chukchi plateau https://data.marine.copernicus.eu/-/764iscr6my

[uniquorn]

On the Atlantic side Argo Float 6904242 shows the West Spitzbergen Current (WSC) peaking at 4.55C with possibly another 6 months before the next warm fluctuation reaches Fram Strait/Barents

https://fleetmonitoring.euro-argo.eu/float/6904242

[Jim Hunt]

There are a lot more SIMB3's this year so feel free to adopt one and keep an eye on it.

There are indeed! My "manual" workflow needs updating 

I think I'll "adopt" one or two of the ones in the Lincoln Sea. Which ones remains to be seen, but here's my own humble effort for 2024H:

Thanks for the heads up. My own version, including the latest data, suggests the call may be slightly premature?

[uniquorn]

I think I'll "adopt" one or two of the ones in the Lincoln Sea.

Great, snowtatos and albedometers. If you ever want to see buoy temps above and below the ice  try adding alpha to the ax.fill lines:

ax.fill_between(timestamp, snow_height, 0, color="white", zorder=2, alpha=0.2)

Following on from https://forum.arctic-sea-ice.net/index.php/topic,4176.msg401422.html#msg401422
some more detail on 2024I

1. Check the snow height using 2cm temperature difference
2. Core ice temp of thin ice warming quickly to -3.5C
3. Ocean temp possibly already affected by warmer atmo. Could just be warmer water.

[uniquorn]

Had an idea to use the SIMB3's for ocean temperature. dtc128 is at roughly 2m depth so here is a visualisation of those temperatures for 2024B to 2024I, mar20-may20
edit: there are some anomalies on dtc128, changed it to dtc125

and a comparison with cmems potential temp at 2.6m
https://data.marine.copernicus.eu/-/pogm3vzoj0

[echoughton]

Jim, I'm sure you've seen this. One takeaway I read is that the research doesn't take into consideration the possibility that the seawater has been rushing underneath the glacier for years or decades before they identified it. Your thoughts?
https://www.cnn.com/2024/05/20/climate/doomsday-glacier-melt-antarctica-climate-intl/index.html?Date=20240520&Profile=CNN&utm_content=1716246010&utm_medium=social&u

[uniquorn]

Argo Float 1902597 found some open water north of Laptev on may25 to surface and upload some profile data. Possible cold eddies at 70m depth. The cooler surface layer was increasing steadily until nearing the Gakkel Ridge. Salinity near surface steadily increasing towards the Atlantic side.
https://fleetmonitoring.euro-argo.eu/float/1902597

https://go.nasa.gov/4e36Hvl (heavy contrast)

[uniquorn]

Had a look at the effect of snow on ArcWatch SIMB3 2023D. Ignoring the roughly 4cm freeboard that was also likely filled with snow, the snow depth is about 28cm based on the 2cm temperature difference chart.
The mean air temperature since oct1 was -21.3C, at the bottom of the snow layer it was -10.8C

https://www.cryosphereinnovation.com/deployment/300434066254600

Update on SIMB3 2023D:
About 24cm snow fell on mar3 increasing snow depth from ~28cm to ~52cm.
Average air temp since oct1 was -22.86C.
Average temp at bottom of the snow layer was -11.98C. Today, may6 it is -7.1C.
Thinnest ice was 1.2m on nov12. Today, ice has thickened by 0.6m to 1.8m

2023D update: Temperatures have risen above freezing for the whole day, peaking at +1C. SIMB3's report every 4hr.

-3.875
-2.75
-2.1875
-1.9375
-0.1875
-0.25
0.625
0.625
0.5625
0.5625
0.9375
1

Snow depth is ~50cm, has settled 1.3cm so far. Nullschool Forecast surface temps to stay above zero for the next 5days.

[uniquorn]

Follow up on 2023D:
Air temp dropped to just below freezing at -0.06C.
Ice/snow interface is at 0C (dtc32)
Core ice temp rising to -2.94C (dtc77)

A closer look at the surface distance data

https://www.cryosphereinnovation.com/deployment/300434066254600

[uniquorn]

Looks like fresh snow on 2023D, temperature dropped to minimum of -4.4C

[uniquorn]

Meanwhile in the Beaufort Sea 2024I has lost 5cm snow.
My calcs estimate roughly 20cm remaining.(default website says 8.2cm)
Buoy temperature at top of the ice is at 0C though it's likely that snow close to the buoy has already melted while the surface sounder is focused further away.

Bottom melt took 2cm on may17 and another 2cm yesterday

https://www.cryosphereinnovation.com/deployment/301434060402500

[uniquorn]

This may be a better representation of ice warming both from above and below using 2024C which has drifted over the Chukchi Plateau. Buoy temps at ice surface again approaching 0C while snow levels further away have only dropped about 5cm.

deployment photo

[uniquorn]

Beaufort/Chukchi SIMB3 snow thickness based on deployment data. Out of range data has been corrected.
Currently ranges from 5cm to 28cm.
https://www.cryosphereinnovation.com/data

edit: somehow missed 2024E which looks like it has very little snow, will include that in the next update.
added Jim Hunt's image

[uniquorn]

Possibly a few cm of fresh snow on 2024E

edit: latest data is back down to 2cm depth, see what tomorrow brings.

[uniquorn]

SIMB3 Beaufort thickness update:

As the first with surface melt, so far 2024E has lost 10cm
2024I has lost 4cm
2024B lost 3cm
2024C, D, G and H lost 2cm
2024F is winning with no loss.

[uniquorn]

Over on the Atlantic side we mustn't forget the AWI meereis buoys.

There are 4 snowbuoys still active showing 20-62cm snow. Thermistor buoy T105 looks buried. Both co-located with SIMB3 2023D showing that 52cm snow reducing to 40cm, recent high air temp of 1.75C, top of buoy temp was 7.5C, so sunny.

[uniquorn]

Quick look at insolation on 2024O:

Perhaps no surprise that incident sunlight minus reflected sunlight increases as the snow layer changes with increase in air temperature. Those peak air temps look too high, they are identical to top of buoy temp dtc0.


https://www.cryosphereinnovation.com/deployment/300434066151880

[uniquorn]

Over on the Atlantic side we mustn't forget the AWI meereis buoys.

There are 4 snowbuoys still active showing 20-62cm snow. Thermistor buoy T105 looks buried. Both co-located with SIMB3 2023D showing that 52cm snow reducing to 40cm, recent high air temp of 1.75C, top of buoy temp was 7.5C, so sunny.

Data appears to have stopped on the 4 active snowbuoys on jun10. Their air temperature readings peak very high, 2023S122 peaking at 4.6C, S125 peaking briefly at 3.6C. Looks like a regular shielded air temp sensor.

Snow buoys: Nicolaus, M.; Hoppmann, M.; Arndt, S.; Hendricks, S.; Katlein, C.; König-Langlo, G.; Nicolaus, A.; Rossmann, L.; Schiller, M.; Schwegmann, S.; Langevin, D.; Bartsch, A. (2017): Snow height and air temperature on sea ice from Snow Buoy measurements. Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, doi:10.1594/PANGAEA.875638.

[uniquorn]

Default SIMB3 snow depth for the northern CAB (no deployment data) 22cm-45cm

[uniquorn]

Update on SIMB3 2024E leading the ice melt with 22cm. Looks like it is maintaining at least a 20cm melt pond. Will be interesting to see if more bottom melt occurs near the shelf break.

https://www.cryosphereinnovation.com/deployment/301434060407510

[uniquorn]

Argo float 7901038 surfaced on jun11 NE of FJL sending a number of stored profiles giving us some idea of recent ocean temp and salinity in the Franz Victoria channel
Profiles shown are 25/10/2023 onwards.

https://fleetmonitoring.euro-argo.eu/float/7901038
map from https://core.ac.uk/download/pdf/480701092.pdf

[uniquorn]

https://fleetmonitoring.euro-argo.eu/float/6904084

4.92C down to 30m in the WSC west of Svalbard

[uniquorn]

SIMB3 Beaufort/Chukchi snow melt update.
I took out recent data for 2024D, details here

https://www.cryosphereinnovation.com/data

[kassy]

With the crossing tracks it´s hard to figure out what goes where. Could you give the paths the colour of the graph above?

[uniquorn]

It's possible but would take time. Cameron already provides a similar facility at
https://www.cryosphereinnovation.com/data with links to individual buoys. I find it useful to look at them all together.
By the way, my charts are adjusted to match deployment data so there are some differences.

[kassy]

If it´s not a simple palette assignment then we can do without. I also like to look at them together but when a lot of them cross tracks it can be hard to follow (probably easier if you follow them closer like you do).

[uniquorn]

SIMB3 2024E began progressively slipping in the borehole on jun22. Currently just over 1m thick.
Bottom half of the temp strip failed at the half way join.
Water temp also higher recently.

[uniquorn]

2024H also slipped in the borehole yesterday with roughly 85cm ice thickness. I'm beginning to think the warmer water is due to a layer of warmer meltwater rather than insolation as once again there are few signs of open water nearby.
https://go.nasa.gov/4eFm1hZ

[binntho]

Insolation through less than 1m ice should be expected? It doesn't need open water.

[uniquorn]

Things may have changed since August 2011 but is a 'measly' 2W/m² (by your standards) enough? 


https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL053738
Changes in Arctic sea ice result in increasing light transmittance and absorption
M. Nicolaus, C. Katlein, J. Maslanik, S. Hendricks
First published: 29 December 2012  https://doi.org/10.1029/2012GL053738

3. Results and Discussion
3.1. Sea-Ice Conditions in Summer 2011

[6] The sea-ice surface consisted of melt ponds and white ice, with the high reflectance of the latter resulting in strongly-scattered solar irradiance. The stations established prior to the North Pole station had open ponds and no snow cover, while surface freezing was observed thereafter. Only the last 3 stations were covered with new snow thicker than 0.05 m. Airborne sea-ice thickness measurements obtained via electromagnetic inductance (EM-bird) along a total length of more than 2500 km resulted in a modal total (snow plus sea ice) ice thickness of 0.9 m, and a mean ice thickness of 1.26 m. The routine sea-ice observations from the bridge show that 42 ± 10% of the FYI surface was covered by melt ponds, while only 23 ± 13% of MYI were covered (Figure S1 in theauxiliary material). These results do match the findings of Fetterer and Untersteiner [1998], who did find melt-pond concentrations of 30–50% for FYI and 15–25% for MYI from AIDJEX data. The main reason for this are differences in the surface topography of FYI and MYI [Eicken et al., 2004]. FYI surfaces are generally smoother, allowing a wider spread of melt water, resulting in large networks of connected shallow ponds. In contrast, MYI is more deformed and favors more distinct but deeper ponds (see photographs in Figure 3).

[7] Considering the entire Arctic, in August 2011, the sea ice extent was 5.5 Million km2with a mean sea-ice concentration of 63%, as observed from passive microwave satellite data (Figure S4). Sea-ice age analyses [Maslanik et al., 2011] reveal that 50% of the sea ice were FYI and 50% were MYI, with MYI dominating along the Greenland and Canada coasts and FYI dominating between 60°E and 150°W (Figure S5). As noted in Maslanik et al. [2011], for the data set used, some FYI is likely to be present even in predominantly MYI locations. Hence, the age data to some degree underestimate total area of FYI, so the effects of the transition from a predominantly MYI pack are likely to be even greater than those described here. Mean solar surface irradiance was 12.3 ± 2.1 Wm−2 (Figure S3), with similar fluxes around the mean in the most central Arctic and minima (8.3 Wm−2) in the Barents Sea and maxima in the Laptev Sea (30.1 Wm−2).
3.2. Light Transmission Through FYI and MYI

[8] Under-ice measurements revealed highest fluxes and transmittances under ponded FYI and thin new ice, while much less light transmits through MYI. At the same time, a horizontal variability of one to two orders of magnitude was found on single ice floes of each ice type. This is clearly illustrated in Figure 2, showing the spatial distribution of light transmittance through MYI for the North Pole station on 22 August 2011. At this ice station, sea-ice thickness was 1.5 to 3.0 m, freeboard was 0.2 to 0.4 m, snow depth was <0.01 m, and ice thickness on ponds was <0.05 m. The nadir photograph, taken from a helicopter, shows the distribution of melt ponds and white ice. Each dot represents one light measurement of a grid flown with the ROV under sea ice. Short-wave transmittance ranged from <0.01 to 0.05 for white ice and from 0.08 to 0.20 for ponded ice. This highlights the high contrast between white and ponded MYI, and in particular the variability across the edges between white and ponded ice. Frequency distributions of light transmission through sea ice for this MYI station and the FYI station of 19 August are shown in theFigure S2. Both histograms (FYI and MYI) show distinct modes for ponded and white ice, resulting in light transmittance through Arctic summer sea ice of 0.22 for ponded FYI, 0.04 for white FYI, 0.15 for ponded MYI, and 0.01 for white MYI (Figure 3). These examples are also representative for the entire data set of approx. 6000 under-ice measurements. However, these modes are less dominant in the complete data set since ice conditions varied over the time of the cruise, in particular through snowfall and surface freezing in the later part of the cruise. Therefore, we consider these two stations as most representative for light transmittance through ponded summer sea ice. Reasons for the strikingly higher light transmission through ponds are the missing surface scattering and the thinner ice underlying the ponds [Eicken et al., 2002]. This demonstrates the important role of melt ponds for the surface energy budget and illustrates why they are often considered windows to the ocean.

[9] Including the different fractions of ponded and white ice for both ice types, this results in a total transmittance that is almost threefold greater for FYI (0.11) compared with MYI (0.04) (Figure 3). Applying the same distribution of ponded and white ice for FYI and MYI onto surface albedo [Perovich, 1996], we find that FYI has a total albedo of 0.37 while MYI reflects 50% more short-wave radiation, a total of 0.62. This finding was expected and confirms earlier studies [Perovich and Polashenski, 2012; Perovich et al., 2011]. But combining these results for albedo and transmittance, we find also that absorption is about 50% larger in FYI (0.52) than in MYI (0.34), favoring a stronger internal warming and melt of sea ice in FYI than in MYI.

3.3. Arctic-Wide Under-Ice Light Distribution

[10] Based on the total transmittance (FYI: 0.11, MYI: 0.04) from the field measurements, and the additional data sets of ice types, ice concentration, and surface solar radiation, an Arctic-wide estimate of light transmission through summer sea ice was derived for August 2011. To do so,ET (Equation 1) was calculated for each grid cell and each day and averaged over the month. We consider August as the best-represented month from our measurements, when sea ice is covered with open and fully developed melt ponds. Also sea ice conditions are expected to be most consistent over the entire Arctic, because autumn freeze-up has not yet started [Markus et al., 2009]. Figure 4shows a map of the Arctic-wide distribution of solar heat input through sea ice into the upper ocean, excluding fluxes through open water. This shows an absolute heat input into the ocean between 0 and 2 W m−2 for August 2011. Regions with predominant FYI show larger heat input than those with predominating MYI, but the absolute flux is also controlled by surface solar irradiance. Including fluxes through open water, the effect of sea-ice concentration (Figure S4) becomes most obvious, particularly in the marginal ice zones, and fluxes within the sea-ice extent reach more than 5 W m−2 (Figure S6). Mean heat flux through the sea ice over the entire Arctic was 0.68 W m−2(mean transmittance: 0.08) in August 2011. Including open water within the sea-ice extent it was 12.3 W m−2 (mean transmittance: 0.40).

my emphasis

[uniquorn]

AWI 2023R25 was the sole radiation station remaining from ArcWatch 2023.
The last full day data was jun4 with 4 datapoints every 6hrs from 00 to 1800. I don't know how to interpret the data though there may be some clues at
https://tc.copernicus.org/articles/15/183/2021/tc-15-183-2021.html
if it is the same device.

[uniquorn]

2024H




2024F at 91cm thickness further south hasn't yet slipped in the borehole and doesn't show the same ocean warming.

[Freegrass]

Them dropping down into the borehole should be easily fixed with a support that rests on the ice, no? Something like you see in the picture.

With the right engineering, you could even make them float on the water after the ice melts. Close those support pipes, so the water doesn't get in, and they stay buoyant, and put a ballast in the bottom to keep it upright. Shouldn't be too difficult or expensive.

[uniquorn]

Starting to see more open water or large melt pond near 2024H. Could explain the warm up.
https://go.nasa.gov/3zm9BM2

[binntho]

Things may have changed since August 2011 but is a 'measly' 2W/m² (by your standards) enough? 

Last time I checked I didn't have any particular standards when it comes to W/m².

The article is informative and they claim that maximum heat transfer through the ice was 2W/m² but they do not tell us how this varies with thickness, which would have been very interesting. We don't know whether they did any measurements below ice less than 1m thick and with meltponds on the surface.

My gut feeling is that if a meltpond is recieving up to 30 W/m² and the ice is only 0.85m thick, then a lot more than 2W/m² would manage to get through. So I would like to remain skeptical.

However, 2W/m² is more than nothing - approximately 15% of average Arctic surface irradiance of 12.3W/m² according to the paper. Which means that even with that number, real heat transfer is happening. The problem is of course to quantify whether it is sufficient to lead to observed bottom melt in this case. I have no idea!

[uniquorn]

My bad, you use measly for tides.

Anyway, there was a correction for that paper which increases the maximum to 13W/m², including open water it rises to 150W/m² so measly no longer applies 
https://agupubs.onlinelibrary.wiley.com/doi/10.1002/grl.50523

[1] In the paper “Changes in Arctic sea ice result in increasing light transmittance and absorption” by Nicolaus et al. (Geophysical Research Letters, 39(24), L24501, doi:10.1029/2012GL053738, 2012), the presented data on solar surface irradiance are erroneous.

[2] In order to generate monthly means of the solar heat input into the Arctic Ocean, among others, the ERA interim (European Centre for Medium-Range Weather Forecasts) data set of solar surface irradiance was used. The original data set consists of eight time slices with integrated fluxes over 3 h each. But in the presented results, only the mean (not sum) of two slices (from 00:00 to 03:00 and from 12:00 to 15:00) was considered, resulting in too low fluxes, approx. by a factor of eight. As a consequence, two text passages (in paragraph 3.1 and 3.3) and three figures (Figure 4 of the main article and Figures S3 and S6 of the auxiliary material) contain too low fluxes. However, the main conclusions of the manuscript remain completely valid and unchanged, since those are only based on relative fluxes, which are not affected by this mistake. The corrected paragraphs read

3.1 Sea Ice Conditions in Summer 2011

[3] …

[4] Considering the entire Arctic, in August 2011, the sea ice extent was 5.5 million km2 with a mean sea ice concentration of 63%, as observed from passive microwave satellite data (Figure S4). Sea ice age analyses [Maslanik et al., 2011] reveal that 50% of the sea ice was First-Year Ice (FYI) and 50% was Multi-Year Ice (MYI), with MYI dominating along the Greenland and Canada coasts and FYI dominating between 60°E and 150°W (Figure S5). As noted in Maslanik et al. [2011], for the data set used, some FYI is likely to be present even in predominantly MYI locations. Hence, the age data to some degree underestimate total area of FYI, so the effects of the transition from a predominantly MYI pack are likely to be even greater than those described here. Mean solar surface irradiance was 110.2 Wm−2 (Figure S3), with similar fluxes around the mean in the most central Arctic and minima (66.0 Wm−2) in the Barents Sea and maxima in the Laptev Sea (230.8 Wm−2).
3.3 Arctic-Wide Under-Ice Light Distribution

[5] Based on the total transmittance (FYI: 0.11, MYI: 0.04) from the field measurements, and the additional data sets of ice types, ice concentration, and surface solar radiation, an Arctic-wide estimate of light transmission through summer sea ice was derived for August 2011. To do so, evapotranspiration (equation 1) was calculated for each grid cell at each day and averaged over the month. We consider August as the best-represented month from our measurements, when sea ice is covered with open and fully developed melt ponds. Also sea ice conditions are expected to be most consistent over the entire Arctic, because autumn freeze-up has not yet started [Markus et al., 2009]. Figure 4 shows a map of the Arctic-wide distribution of solar heat input through sea ice into the upper ocean, excluding fluxes through open water. This shows an absolute heat input into the ocean between 0 and 13 W m−2 for August 2011. Regions with predominant FYI show larger heat input than those with predominating MYI, but the absolute flux is also controlled by surface solar irradiance. Including fluxes through open water, the effect of sea ice concentration (Figure S4) becomes most obvious, particularly in the marginal ice zones, and fluxes within the sea ice extent reach more than 70 W m−2 (Figure S6). Mean heat flux through the sea ice over the entire Arctic was 4.70 W m−2 (mean transmittance: 0.08) in August 2011. Including open water within the sea ice extent it was 32.9 W m−2 (mean transmittance: 0.40). …

[binntho]

Fair enough, what goes around comes around ... and you are right, these figures are not so measly now.

"measly" - 16th century, pig infected with measles! Modern meaning since 19th century "paltry, meager, scanty".

[uniquorn]

fig2 and 3 from the same paper.

[binntho]

The difference between FYI and MYI is very interesting - it seems the latter has fewer but deeper meltponds? Which makes FYI even more likely to melt faster than MYI (in addition to higher saline content and brittleness).

If I remember correctly, bottom melt is generally more signifcant than top melt, as shown by the bouys, although timing is different. The normal assumption is that bottom melt is caused by irradiation through the ice, but that is maybe not correct?

We have often mentioned the unseen factor of heat transport within the ocean, whether from down below through turbulence, or from currents rising to the surface due to changes in bathymetry. Meltwaters from the rivers are of course also a factor, but I doubt if it is significant once you get away from the deltas.

FYI covered in meltponds will absorb a lot of solar energy and, depending on thickness, will allow a significant portion to penetrate through to the underlying water. But which of the two is more conducive to melt? Energy that is absorbed within a 2.5 meter thich FYI flow will raise the internal temperature of the ice, and possibly create pockets of warter or expand pockets of brine. At the end of the day, I guess this is irrelevant to final volume loss unless the ice manages to melt through, in which case it might speed the process.

Energy that reaches the underlying water, on the other hand, will cause bottom melt directly and straight off the bat. Another question is when dispersion becomes sufficient to enable open water to heat enough to cause widespread bottom melt under the ice. Water absorbs incoming radiation and heats at the surface, but that in itself will not cause bottom melt in neighbouring floes unless some sort of churning and mixing takes place, possibly when floes drift in over open water.

[oren]

If I remember correctly, bottom melt is generally more signifcant than top melt, as shown by the bouys, although timing is different. The normal assumption is that bottom melt is caused by irradiation through the ice, but that is maybe not correct?

It has been my impression, following the many buoy chart posts by uniquorn and others over the  years, that bottom melt starts soon after air temps reach close to zero.
The ice floats in a giant heat sink of saline water, and can only remain stable when  there is a gradient of heat flow towards the surface, or at least towards the middle layer of the floe. When that gradient is gone, following the warming of the core layer, the bottom-most layer starts melting into the ocean.
Obviously, energy added directly to the water or to the lower ice layers via insolation speeds up the process.

[uniquorn]

If I remember correctly, bottom melt is generally more signifcant than top melt, as shown by the bouys, although timing is different. The normal assumption is that bottom melt is caused by irradiation through the ice, but that is maybe not correct?

It has been my impression, following the many buoy chart posts by uniquorn and others over the  years, that bottom melt starts soon after air temps reach close to zero.
The ice floats in a giant heat sink of saline water, and can only remain stable when  there is a gradient of heat flow towards the surface, or at least towards the middle layer of the floe. When that gradient is gone, following the warming of the core layer, the bottom-most layer starts melting into the ocean.
Obviously, energy added directly to the water or to the lower ice layers via insolation speeds up the process.

Agreed partly, though I would turn it round. The sea begins to freeze when the air temperature is cold enough and bottom melt starts when it isn't, and the ice thickness/snow depth should make a big difference to the temperature gradient within the ice.
 However, if we stay up to date and look at 2024I, the first bottom melt occurs when 3day trailing air temps were around -4C and the second at -2C, with roughly 25cm of snow at surface. Maybe the thickening on may14 was still fragile.

2024I
Ice Thickness 109cm
Snow Depth 22cm
Ice Type MYI
Surprisingly thin MYI. Adjacent FYI is about the same thickness, with less snow.

The ratio between top and bottom melt depends a lot on location and time of year. These Beaufort buoys may all melt out before bottom melt gets a chance. Once the buoy slips in the borehole the whole environment changes anyway. As we know, the buoy also affects its surroundings.



Some background on SIMB3:
https://www.cryosphereinnovation.com/docs/simb3-capabilities
SIMB3 Capabilities
Designed for unattended extended operation in some of the world's harshest environments, SIMB3 gives you the capability to remotely measure ice, ocean, and atmospheric data from a singular, integrated platform.

Environmental capabilities
SIMB3 spans from the ice into the ocean and air, bridging three environments simultaneously. It is equipped with a fully sealed and buoyant hull and can be installed in existing ice or in open water.

SIMB3 can measure ice from 0 m (open water) to 2.5 meters thick. It is designed specifically for measurements of seasonal ice (first-year ice) that fully melts out each year. It's buoyant design allows it to capture data long into the melt season and even survive refreezing for multi-seasonal operation.
SIMB3 is capable of year-round operation in maritime environments with temperatures down to < 40 C.

[uniquorn]

SIMB3 2024E began progressively slipping in the borehole on jun22. Currently just over 1m thick.
Bottom half of the temp strip failed at the half way join.
Water temp also higher recently.

2024E thickness now 90cm, losing ~3cm/day

some fog from mosaic exp

[uniquorn]

Had a look at SIMB3 2024o. The sounders aren't working but the temperature strip is (mostly). It's fairly easy to see the snow layer reducing from the temperatures.

incidence minus reflected peaking at 227W/m²

2024o Initial conditions
Ice Thickness 172cm
Snow Depth 51cm
Ice Type MYI
Large MYI pan. Appears 2nd year since surface is quite level and may have experienced little surface melt. Equipped with SnowTatos.

[be cause]

That 51cm of snow is a lot  more than the 0 cm that GFS sees .. if is it purely a guess , why do they bother ?

[uniquorn]

My mistake, 51cm is the initial snow depth. By clicking on the images it's fairly easy to see it has reduced to about 20cm.
Very few bother to look at them 

Was just looking at 2024J, sounders are working, currently has ~30cm snow, lost 4cm to bottom melt but it is already heading to the Fram Strait.
No air temp or ocean/ice bottom provided on the Lincoln sea buoys so I have less interest in them. Albedometers are interesting but without the air temp not so useful. Maybe more interesting later in the season.
https://www.cryosphereinnovation.com/deployment/301434060407490

[uniquorn]

update on 2024D
https://www.cryosphereinnovation.com/deployment/301434060405490

[oren]

I have moved 7 posts about fog to the freeform seasonal thread, as they were off topic here.

[uniquorn]

Float 6903564 surfaced on jun30 close to the entrance to the St Anna Trough sending a number of profiles back. The drift track while under ice is estimated as a straight line between known coordinates but gives us an idea of what is going on below the ice.
Profiles 495-512 are missing, 28/12/2023-26/02/2024
Data shown is 22/12/2023-30/06/2024, highlighted in the first image.

https://fleetmonitoring.euro-argo.eu/float/6903564

[Steven]

The buoys in the Lincoln Sea are showing a spike in melting in the last few days, especially buoys 2024N and 2024L.

https://www.cryosphereinnovation.com/data

[uniquorn]

Snow depth may be underestimated by 13cm on the website for 2024L. Still about 10cm of ice melt though, maybe melt pond drainage.

https://www.cryosphereinnovation.com/deployment/301434060104850