The melting of the Arctic ice may be laid directly to this effect. There is a part of the Pacific Rift “ring of fire” that extends into the relatively shallow Arctic Ocean, and it has been extraordinarily active of recent, melting the ice cap from beneath. The resulting outflow of relatively fresh water (low salinity), a surface flow, has resulted in the replacement of warm flows from the Gulf Stream flowing INTO the Arctic ocean at some depth (deep current), further exacerbating the melt effect, until it cools sufficiently.
All water, saline or fresh, assumes a temperature of approximately 38 degrees F (abut 4 gradients C) at depth from 500 to 1,500 meters depth, and this temperature is relatively stable to even great depths, except at those points where there are subsurface volcanic vents. At very great depths, the enormous pressure keeps the escaping gas from actually bursting forth as a gas jet, but the water in the immediate vicinity may be superheated to 700 degrees F or more, but because of the pressure, remains a liquid. These jets of water, rising rapidly through sometimes several MILES of water under a decreasing pressure gradient, warm the layers it passes through, setting up a vast thermal current from the depths.
Even a very few years ago, none of this was understood, or even suspected.
Convection currents of greater or lesser force depending on lava output which varies according to water depth? Sounds very reasonable.
Thank you for taking the time to give us this explanation. Fascinating, really.