It was during the period when the entire area was under water! They Called it the Short warming period.... it happened... everybody left Greenland it couldn’t grow Food because it was a swamp like! If It was really hot maybe it could grow rice!
I think you are misreading something. Most of Greenland (not counting ice) is well above see level running from hundreds of feet to thousands of feet. If all the ice in the world completely melted, it would only raise the sea levels 150 feet.
So how did Greenland get completely flooded c. 1600 AD without also flooding all of Florida and most of Southern England?
I think you are reading about one particular area of Greenland where warmer wheather turned the permafrost into mud.