Glacial melting can have quite fast effects. For example when a glacial lake is building do to melting and the ice dam holding back all the water breaks. The co

Glacial melting can have quite fast effects. For example when a glacial lake is building do to melting and the ice dam holding back all the water breaks. The content of the whole glacial lake can be swooped to the oceans in one flush. It doesn't even have to be melted water. Rivers under the ice due to melting ice can transport whole ice sheets to the coast and into the oceans. Carrying all the weight of the ice with it, into the oceans. Now the ice sheets have a MASSIVE weight that pushs on the whole antarctic continent. Releasing all that weight has an effect on the earth crust. Much less weight on the antarctic continent and overall more weight on the oceans. This will result in tensions in the earth crust. We know how these are released: Earth quakes. Earth quakes can also result in tsunamis. A lot of coastal cities are not really prepared for tsunamis. Just telling a story what CAN happen.