For long sea floor volcanoes were ignored as it was thought that there effect on atmosphere is minimal, as they lie buried in water. However, a recent study has shown that unlike the earth surface volcanoes, underwater volcanoes bursts rather than spew at slow pace. Underwater volcanoes affects the climate by emitting varying levels of carbon dioxide into the atmosphere.
Higher levels of carbon dioxide emitted into in the atmosphere, can trigger a cycle of global warming. These volcanoes have the capability to alter climate. They spew lava, carbon dioxide and other elements into the deep oceans. The carbon gets trapped in water that is circulating & gets cycled to different regions of the ocean. From these regions it gets caught up in upwelling currents and gets radiated to the atmosphere. Assumed to be in a steady state, underwater volcanoes get affected by small and large forces alike & affect atmosphere-ocean coupling in a great manner.