New research reveals that polar ice is melting from below, as two scary scenarios unfold.

Ice shelves: These hybrid formations hug the coasts of Greenland and Antarctica, with part of the shelf floating and part on land. They serve to put the brakes on the flow of massive land glaciers into the sea. They are collapsing virtually everywhere, most notably the Thwaites Glacier (otherwise known as the Doomsday glacier) and the Pine Island ice shelf. It has slowly become clear that the warming waters beneath the shelves is accelerating the melt rate, with cascading effects.

Land ice sheets melting from the foundation up: What is not obvious, however, is the behavior of trillions of tons of land ice, as billions of gallons of meltwater from the surface of the ice sheets flows down to the base of the mass. Falling meltwater is converted to kinetic energy as it flows downward, which heats the pools forming at the foundation of the ice sheet. This invisible process is accelerating at unprecedented rates.  The meltwater also behaves as a lubricant that increases ice flow as well as the quantity of ice discharged into the ocean.

The Antarctic ice sheet averages one mile thick and contains about 30% of the planet’s fresh water. It is already responsible for about 4% of sea level rise around the world.

Simply put, if this ice (not to mention more trillions of tons on the Greenland land mass) continue to accelerate into the Southern Ocean, the effect on coastal sea level rise will be catastrophic. Equally catastrophic will be the change in the ocean’s basic chemistry as more fresh water is added.

Fun Fact: the Twaites Glacier is about the size of Great Britain. The rate of melt has doubled in the past two decades.