A Warning From the Last Ice Age?

The melting of the polar ice sheets is an obvious, dangerous consequence of global heating. This melt would increase sea levels, especially endangering coastal and island communities. It's consequently important to know how quickly sea levels could rise. Previously, best 'guestimates' used date from repeated satellite imagery. An approach, based on the study of ancient 'grounding lines' suggests, however, that the ice sheets can melt very much faster (https://www.theguardian.com/environment/2023/apr/05/ice-sheets-collapse-far-faster-than-feared-study-climate-crisis). The 'grounding line' approach (published in the journal, Nature), uses high-resolution mapping of the seabed off Norway's coast. At this location, large ice sheets collapsed into the sea at the end of the last ice age (20,000 years ago). The 'grounding lines' are small ridges, parallel to the coast, formed at the points, where the ice sheet base met the ocean. As tides lifted the ice sheets up and down, the sediments were squashed, twice a day, into these ridges. The 'grounding line' retreats towards the shore, as the base of the ice sheet melts. This leaves behind sets of parallel ridges. Measuring the distance between ridges, is a measure of the speed of the ice sheet collapse. Speeds of between 50 and 600 metres per day were obtained in this study. This means that ice sheets can collapse up to 20 times faster than had been suggested by satellite studies. Rapid spurts of ice loss, over (at least) several days, also seemed evident. It's obviously pretty important to know whether an ice sheet collapse, assumed to take 200 years, could actually occur in only 20!