tried a discussion in the Melt Season thread ...a lot is happening which categorically *isn't* being captured in our traditional metrics.
That thread has been hijacked by legacy extent trackers, 10-day wx disaster forecasters, and self-nominated Nobel laureates (for seasonal weather prediction, ice physics outcomes six months out, even 2022 melt season finale.)
a 'solid pack' view of arctic ice struggles with 'real world' conditions
Looking at Hycom ice thickness at the north pole from July 28th through the Aug 19th photo forward to the Aug 28th forecast, the ice is shown having a fairly narrow range of thickness, notably 0.75 m at the time the Polarstern was there. It continues to thin moderately over the forecast week but part of that is just ice pack motion bringing thinner ice in. Click to see daily thickness.
Piomas thickness could also be tracked down but it too has zero knowledge of melt pond specifics in its model.
Since no representative measured ice thickness data has been released, actual thickness remains unknown. It's a pity that Mosaic holds back data to 2023 instead of informing the current melt season.
-- What do we even want 'thickness' and 'volume' to mean when melt ponds of various depths and evolutionary stages occupy fully half the scene, extending out beyond the horizon?
-- Did ice physics models have any real awareness of current conditions at the scale needed? Now that we have data, has it been assimilated? No.
-- What is the effect of draining melt ponds on floe buoyancy and does that fool freeboard satellite altimeters?
-- Could 'averaging' somehow average away melt ponds and leads when they nevertheless dominant the scene at all scales? How is the remaining ice scored after melt ponds drain?
-- Who knew in advance what 88-90º would look like? Nobody. If the PS had not taken those photos, would we ever have known? No.
Meanwhile the PS has left the pole, already 150 km south along the 105th meridian looking for a suitable floe to moor onto. This will take them back into satellite range and back into the TransPolar Drift which is not drifting, but not quite back to their original October lat lon of 85.1 134.3. Sentinel-2 can image melt ponds on clear days (lol) to 10 m resolution (not quite enough).
According to Ascat, this is FYI formed in the Laptev. It might have maxed out as 2m in late February but is assuredly thinner by now, sub 1m. It's questionable whether they will find a thick enough floe to work on safely -- freeze season is still six weeks off and they'll be leaving before that really sets in. The better CAB floes are off on higher different meridians, say the 180th meridian to Wrangel.
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Forum discussion of melt pond energetics -- a very big topic in Arctic academia -- went way off the rails. The sky and water are blue from Rayleigh elastic scattering, not adsorption of light and conversion to heat. Insolation energy at the surface is largely at visible wavelengths. Neither H
20 nor ions like Na
+ or C
l- have any ability to accept photons at these wavelengths.
Melt ponds are clear to the bottom regardless of salinity. The ice bottoms of melt ponds are reflective white, scattering incoming light in all directions including down. Melt pond albedo is thus less of a drag on fractional BOE than open water albedo. Indeed shallow melt ponds have an albedo of 0.4-0.5 per NSIDC. Yet ROV images show some sunlight manages to pass below everything above.
https://www.sciencedirect.com/science/article/abs/pii/S0165232X15003171Adsorptive impurities abound even though the scene looks pristine: wildfire ash, miscellaneous industrial and agricultural pollutants and plastics, thermokarst shore erosion, river sediment, fallen aerosols, desert dust, volcanic ash, flakes of unburned bunker fuel, algae and copepods channeled into the ice bottom, and so on and on. Those do convert light to heat (molecular motion) and that heat equilibrates with the surrounding water.
In summary, a good portion of incident sunlight energy is scattered back into the atmosphere, melt ponds lessening that somewhat. The rest is absorbed somewhere in the 'water column', mostly in the upper few meters, the exact apportioning depending on many parameters that change locally over the melt season. The heat cannot readily equilibrate because of diffusive and conductive barriers but still manages to affect many processes.
The hycom image needs a click to display its thickness boxes. To make, I put a one pixel dot right at the pole and put the color picker too on it there so that it also highlighted the right box on the thickness palette, then cropped the stack of co-screenshots.