Large areas of the tundra are wetlands but so far tropical...

Large areas of the tundra are wetlands but so far tropical wetlands have been the biggest driver of growing methane emissions over the last decade or so.

The question with frozen methane, whether in permafrost or as hydrates on shallow arctic continental shelfs is how much will be devoured by microbes before it can reach the atmosphere. Obviously with violent explosions like craters in Russia,, microbes won't have a chance to feed but those are few and far between compared to slow leaks as frozen deposits of methane thaw. So you're right, it could be a tipping point but it's unclear what the magnitude of that tipping point could be.