There is documented evidence of tremendous icedams breaking in the scablands of Washington State and in the Great lakes, sending water down the Columbia Gorge and the Mississippi River, respectively.
I hadn't heard of the Antarctic Meltdown, but that also could account for evidence of 1000 foot waves throughout the world.
One analyst suggested it's almost as though a female gave birth to cubs deep in a den while all the world above was destroyed along with the Cheetahs running around. A massive widespread tsunami would do the trick every single time (provided these animals preferred very flat alluvial plains for their habitat).
I've read that when the fresh water ice dam broke at Hudson bay that the water rushed out then the humungus ice sheet covering the lake broke in half and it too rushed into Hudson Bay causing outrageous tsunamis. The water level worldwide was raised by a foot overnight.
Here in the Pacific NorthWest we have ample evidence for the floods, up to 120, that created the WA state scablands and deepened the Columbia River. All of the western Montana valleys were full of meltwater, held back by an icedam near Thompson Falls. Periodically it would break, sending cubic miles of floodwater racing to the pacific. Spokane falls is a result of that deluge/gouging action.
Mt Saint Helens happened in 1980, there is ample proof of a 300 foot high wave that hit the Olympic peninsula/Pac NW coast hundreds of years ago, caused by the Cascadia fault. Point : natural forces operate on their own timescale, chicken little algore and his fearmongering has nothing to do with causing it, it’s Mother Nature doing her thing.