This phrase is interesting:
Colder and/or saltier seawater is denser than fresher and/or less salty seawater. Waters in the Arctic depths remain trapped near the bottom. They do not mix much with surface waters. Almost no heat is transmitted all the way up to the underside of the ice.
I agree with you Anart...in your post above...
I hope I would not sound "flippant", but even though I can understand the Arctic is much bigger than an analogy I am going to try to use, the principle seems to be about the same:
Imagine you have a pot of water sitting outside in below the freezing point of water ( > 32 degF./0 degC. ) & it forms a skim of ice on the surface of the water, or perhaps you could imagine a pot that has many icecubes floating in that water. If you take that pot & place it on a burner, the heat at the bottom makes the molecules vibrate faster as they heat up & the heat will then rise up to the suface where the ice is. Whether it is a low heat or a high heat, the heat(heated water) will eventually reach the underside of the ice at the top, & dependant on the duration of the heating time/amount of heat generated, the ice will likely start to melt from below, & the below ice water will heat up, even if the ice continues to form above.
Maybe that analogy is over simplified, but since it seemed to me that the "principles" are the same. So, if a volcano is erupting below the surface & acting as a "heat source", no matter the depth, that warmed water is going to rise, & as it rises it encounters even warmer water, & so on til it reaches the ice.
Makes sense to me, although I am not a scientist. I have certainly heated pots of skim ice water here in the North while outside in below freezing weather & have boiled water for both cooking & making hot beverages. (It is a also a means to purify water if someone found the need.) So I know this works on this smaller scale. Would it not work the same as in a larger scale? Regardless of if it was salty water or not?
This "Whoi" I think... just might be full of "Hooeey".