Greenland’s ice shelves hold back sea level rise. There are just 5 left.

The vast floating ice platforms of northern Greenland, unrivaled features of the northern hemisphere that keep our seas lower by holding back many trillion tons of ice, are in stark decline, according to new scientific research published Tuesday.

These northern Greenland ice shelves, as they are called, have lost 35 percent of their overall volume since 1978, the research published in “Nature Communications” found. That’s equivalent to a loss of roughly 400 billion tons of floating ice that acted like the stopper of a decanter, preventing glaciers from flowing into the sea and accelerating sea level rise.

And now there are only five large shelves left, stretching out from their fjords toward the Greenland Sea and the Arctic Ocean. That includes three major ones — Petermann, Ryder and Nioghalvfjerdsbrae (often referred to as 79 North for its location in degrees Latitude) — whose respective glaciers could ultimately account for 3.6 feet of sea level rise if they were to melt entirely — a process that would take centuries to play out.