https://phys.org/news/2018-06-wrinkle-history-west-antarctic-ice.html

Surprising new data and ice-sheet modeling suggest that between roughly 14,500 and 9,000 years ago, the ice sheet below sea level partially melted and shrunk to a size even smaller than today—but it did not collapse. Over the subsequent millennia, the loss of the massive amount of ice that was previously weighing down the seabed spurred uplift in the sea floor—a process known as isostatic rebound. Then the ice sheet began to regrow toward today's configuration.

"The WAIS today is again retreating, but there was a time since the last Ice Age when the ice sheet was even smaller than it is now, yet it didn't collapse," said Northern Illinois University geology professor Reed Scherer, a lead author on the study. "That's important information to have as we try to figure out how the ice sheet will behave in the future."