We will explain more on ice sheet collapse later, but prior to about 1900, we know sea level was stable for several thousand years. (washingtonpost.com)
This process is difficult to accurately model, but rapid ice sheet collapse would certainly result in dramatically higher rates of sea level rise once this critical threshold is passed. (antarcticglaciers.org)
Joughin, I., Smith, B. E. & Medley, B. Marine ice sheet collapse potentially under way for the Thwaites Glacier basin, West Antarctica. (nature.com)