Totten Glacier’s underbelly is being eroded by warm sea water flowing hundreds of kilometres inland after passing through underwater "gateways".
A study estimates about 5 500 of these ice sheets could vanish by 2100, affecting millions of people.
Figures from the National Snow and Ice Data Centre indicate six or seven- year low over past three decades.
The world has become too hot for the aptly named Exit Glacier in Alaska. Like many low-altitude glaciers, it’s steadily melting.