The meteor hits the atmosphere; makes a noise; the dams break; massive quantities of water spill out into the St. Lawrence and Mississippi valleys.
Those waters spread out over the Gulf of Mexico, etc. and interrupt the haline circulation in the North Atlantic.
A sudden refreeze happens. The Sa'ami find they can travel to America along the edge of the winter sea-ice (eating seals the whole way), and arrive there just in time to find all the large game dead, the sabertooth tigers and direwolves expired (from want of game), and the world to themselves as the TOP PREDATOR.
All makes sense. Yup.
About 4,000 years later the same sort of thing happens in Antarctica. Large icedams surround the (much extended) coast, kept cool by the circumpolar cyclone, and melt water backs up behind them.
A meteor hits the atmosphere with enough force to make a loud noise which causes cracks to occur in the icedams which then break.
Vast quantities of water are suddenly released into the ocean causing a tsunami that rushes Northward to flush every coast on Earth of every living thing.
Only those who lived on top the coastal mountains or far inland, or in deep caves, survived to tell the story.
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.
I have come to the conclusion based on various inputs that there was something bad that happened about 8,000 years ago. Can you recommend any links?