I have more satellite data that I have been hoping to present this season but due to my system breakdown and cost of repairs US$1,500, I have not been able to access the images I would have wished to put out this season on some debates. (Difficulty is that the firmware reader of data is incompatible with all PC and MacIntosh so finding people and spares is very hard for me to fix it.)
I can on this debate offer you a few images that I have put on my Curriculum Vitae that can be downloaded from Academia.edu. They are not of best resolutions, nor all of the images available that are highlighting this matter, but every bit will, nevertheless, help.
It is costly to produce images which provide optic side scans and repeat scans (multiplexing) of sea ice as this involves flying satellite constellations repeatedly in different angles and one after another. It is getting ever easier and one day all this is probably routine. Also a Fournier triangulation is avoided to spot visually a target such as a moving warship and to identify which ship or submarine has surfaced from the Arctic sea ice. It is tedious exercise to keep tabs (particularly on nuclear submarines as they are small and can disappear quickly back into ice).
For our discussion here we are interested about the formation of the leads, why and where they form:
Multiplex imaging with satellite cluster produces images of entire Arctic Ocean cloud-free during sunlight season, including the infrared and UV-scanners that identify sources or ships' heat or electric lights, whatever. On CV page 10 you can see how the continuous breakwater pulse propagates within the Arctic Ocean and weakens the sea ice from the estuary onwards. (The large image on the top.) Typically ultimate "C", penultimate "B", and antepenultimate "A" ice floes form from the Russian coast running their weakened seams perpendicularly to Canada where the ultimate "C" typically hits at the Western Last Sea Ice Area (Western - LIA) where the turning process causes opposite stress point, thus segregating the ultimate "C" and penultimate "B". There are two of these, but only one C/B is shown on my CV, both of them would be interest to this discussion.
There are couple other processes on the Arctic Ocean:
Page 8 The antepenultimate "A" facing the Atlantic runs on its own with the alternating zebra patterns of green and white on this image (result of breakwater waves or cells rolling on shallow sea).
The density differentials form the colours here as the river water from Russia moves along and rolls a bit like Swiss roll on its way to deep water near Fram Strait. The high density water is white as sea surface is lower than the ocean median ice surface (the median lines are highlighted on image for clarity), the low density river water is green due to it representing higher than the ocean median ice surface (due to its being less saline, it needs higher water column than saline water to keep ocean surface at equilibrium pressure).
The white colour forms over the dense water where ocean surface is lower than median and fills with drift snow. The green colour forms on the crest that is higher and without the drift snow that accumulates on troughs. The snow accumulation further amplifies the effect anchoring even more snow over the dense, saline rollers.
Because of this constant rolling of Swiss rolls between the ocean floor and its surface (sea ice), there is an overall current which has higher gravity potential and faster forward movement on surface, this then marks the boundary between antepenultimate "A", and penultimate "B" as the B flows slower than A.
These things have also changed over the years as ice in overall has pulverised and not been forming uniform films, but overall show the effect of North Asian rivers discharging onto the Arctic Ocean and forming weak points by supply of warmer water and its mixing and dragging heat out from warmer waters beneath - then maintaining a thinner ice along a narrow channel which presses against Canada (Western Last Sea Ice Area, by splitting the sea ice C/B and B/A, with B/A junction also running at different speed.
The differential movement on p. 8 is shown by 12 perpendicular secondary cracks (highlighted) on the main B/A crossing from Komsomoletski Island to Ellesmere Island.
Page 9 focuses on vortices or breakwater cells that fall into the deep channel, warm up aggressively and surface like cumulus cloud with the centre of pancake elevated with edges bending down and below median and filled by snow. These curving sea ice "spaghetti" edge formations are rare in comparison of the rectangular edge formations caused by breaking ice and re-freezing ice.
The rest of my Curriculum Vitae outside pages 8, 9, 10 are irrelevant to this forum.
https://www.academia.edu/5859691/Curriculum_Vitae_for_Exploration_and_ResearchIt's useful to read the Wikipedia entry on Pressure Ridges, and another entry about Stamukha.
https://en.wikipedia.org/wiki/Pressure_ridge_(ice)
https://en.wikipedia.org/wiki/Stamukha
Pressure ridges are the thickest sea ice features and account for about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice.
One of the largest pressure ridges on record had a sail extending 12 metres (39 ft) above the water surface, and a keel depth of 45 metres (148 ft). The total thickness for a multiyear ridge was reported to be 40 metres (130 ft). On average, total thickness ranges between 5 metres (16 ft) and 30 metres (98 ft), with a mean sail height that remains below 2 metres (6.6 ft).
Interesting. stamukha (the grounded version of ridges) are most often found at depth of 20m which corresponds to Niall's depth chart above. Additionally, stamukha is a Russian word and the crack in question is found on the Russian coast.
So far, the shoe fits !!
So, a good working theory is that the repeating initial crack in the ESS is found at the 20m depth stamukha line.
If I were to imagine how the works in total, you have incoming warm Atlantic water entering the Arctic and Coriolis forces have it hugging the Siberian coast until it hits the stamukha wall and is forced toward the surface which is just a few meters above. Sound reasonable ?
Thanks for the wiki link Oren.
Edit: Alternative / complementary view is that the opening of this crack is also influenced heavily by wind. Looking at Aluminum's most recent post (#339) it seems like the crack was pretty wide a few days ago and then shut down with a change in wind direction.