OK, 600 square kilometers, lets rough that out and call it 200 square miles, which is a piece of dirt 10 miles by 20 miles.
Don’t get me wrong. But I’m betting there have been plenty of years when the Cascade mountains in Or/Wa and BC have had like 40-70 foot base of snow on them.
And the Cascades add up to a little more than 20 square miles.
I’m just fudging around a bit, but seems to me there are other things that in the greater scheme make this into small potatoes.
Add in the interaction between the earth and moon and really mess with your figures.
I believe the moon/earth/tide action is slowing the earth down and sending the moon further away.
The glaciers over North America and Asia only 20,000 years ago would dwarf that reservoir. They put 400 feet of water that is now in the oceans on top of the continents.