More interesting crumbs of data coming in. The crumbs sure seem to point to my doming theory. You can see the close diffuser is dealing with a dome. The ice doming up causes the "doughnut pattern" because the plume no longer touches the ice. The warmer water travels out and melts the outside ring of the circle. If the dome does not break by the time aeration turns off then the ice has time to refreeze overnight and tomorrow when the aeration resumes the ice lifts even further off the water making it even more difficult to melt a hole. It appears even the quad is struggling to stay open even though it's hole was open all the way to the shore. The windmill hole is totally gone. Meanwhile the ONLY diffuser with the pipe in the plume is still wide open.

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