I absolutely do not know the process for aquifer formation, however:
* the ice age left immense amounts of water behind, including hidden under ground ice bergs that took thousands of years to thaw
* if you had a lake in a place, that sort of saturation would lead to an aquifer I think. Then the lake disappears, but the saturated ground remains, hidden from the air and sun, until drained
Yeah I have no idea what they are referencing either. Ice sheets are called as such because they sit on top of the continents. Apparently North America was actually compressed downwards by the last sheet and is still basically rising back up.
Maybe they are thinking of permafrost or something? I'm not sure how deep that gets at the Northern reaches like Svalbard. But most of the land on earth is not permafrost for a long time now.
* the ice age left immense amounts of water behind, including hidden under ground ice bergs that took thousands of years to thaw
* if you had a lake in a place, that sort of saturation would lead to an aquifer I think. Then the lake disappears, but the saturated ground remains, hidden from the air and sun, until drained