If a volcano erupted, under the ocean, the atmospheric cooling affect of sulfur and dust is scrubbed by the ocean water, giving you just an ocean warming affect that can cause CO2 to be released. The crust is much thinner under the oceans, allowing the plates to move easier and heat to seep from the mantle.
Is everyone aware that there a place under the Atlantic Ocean where the earth's mantle is exposed without any crust covering it.
Mission to Study Earth's Gaping 'Open Wound'
There was another discovery of oceans of water, under the crust, in the upper mantle, below SE Asia and USA.
Huge 'Ocean' Discovered Inside Earth
New Evidence for Oceans of Water Deep in the Earth
I put these two discoveries together; mantle exposed and the upper mantle water, to speculated that a large breech in the crust, caused hot mantle water to pour into the Atlantic, creating that exposed scar.
The earth is integrated and climate science is not fully addressing the affects of the balance of the water in the atmosphere, the oceans and in the inner earth. El Niño and La Niña are both ocean water affects, that can determine whether California gets a lingering drought or too much rain from an atmospheric river of water. This has little to do with CO2, but manmade gets all the credit.
El Nino was first observed in the 1600's by fishermen. This is connected to a warming and cooling of ocean water at reoccurring place.