Glacial Lake Iroquois

As the Laurentide glacier melted several thousand years ago, retreating to the frozen north, it left behind a massive number of lakes, rivers, drainages, and waterways. One such was the massive lake now known as Glacial Lake Iroquois. This lake stood where present day Lake Ontario stands; it was hundreds of feet deeper than Lake Ontario. Its access to the Hudson valley was blocked by the Laurentide ice sheet. When this gave way, suffering the melt off, the lake suddenly drained, and the massive flood water thundered down the valley and into the Atlantic ocean.

So cold were the waters of that lake that they overwhelmed the Gulf Stream and cooled it off, this may have triggered the Younger Dryas, a cooling period that last for over a century.

And here I thought the Ice Age just made that stuff up in the movie.