Now we know how much ice will melt from Greenland at the very least

Published 29-08-2022

Based on two decades worth of measurements instead of models, glaciologists have for the first time determined the minimum ice loss committed from the Greenland Ice Sheet as from the climate warming so-far. This leaves out the uncertainty of any positive or negative future climate scenario, letting us know the absolute lower bound for what’s to come.

Note: This article has been edited in order to correct an error in mass loss; originally the article stated a mass loss of 110 quadrillion tonnes, the correct number is 110 trillion tonnes. 

Even if the whole world stopped burning fossil fuels today, the Greenland Ice Sheet would still lose about 110 trillion tonnes of ice leading to an average of global sea level rise of at least 27 centimetres.

By looking at the climate in the Arctic from 2000 to 2019 and the imbalance it has created in the Greenland Ice Sheet, researchers have calculated that the shape of the ice is set in motion to correct this imbalance – inevitably – by losing 3.3 percent of its current volume, which corresponds to the numbers mentioned.

Actually, this is a low estimate according to the lead author on the study just published in Nature Climate Change, Professor Jason Box from the National Geological Survey of Denmark and Greenland (GEUS).

“It is a very conservative rock-bottom minimum. Realistically, we will see this figure more than double within this century,” he says and elaborates:

“In the foreseeable scenario that global warming will only continue, the contribution of the Greenland Ice Sheet to sea level rise will only continue increasing. When we take the extreme melt year 2012 and take it as a hypothetical average constant climate later this century, the committed mass loss from the Greenland Ice Sheet more than doubles to 78 cm.”

Notably, this study is only looking at the situation of the Greenland Ice Sheet, not considering the mass loss from Antarctica or other glaciers around the world.

New ice equilibrium
In the recent (2000–2019) climate, the Greenland ice has built up a disequilibrium which will inevitably correct itself by reducing total mass by at least 3.3 percent in order to regain equilibrium at a new average snow line in a higher alteration. (credit: The Geological Survey of Denmark and Greenland, GEUS)

The snow falling on the ice during winter turns into new ice over time. If the snow does not melt away during summer, that is. In order for the ice sheet to be in equilibrium, the added mass must equal the lost mass. In a stable climate, that’s the case. If a hot summer causes the layers of snow to be lost by melt, that snow will be missing in the mass budget for years to come, creating a mass budget deficit or disequilibrium.

It is this disequilibrium Professor Box and colleagues has calculated the consequence of based on more than a decade of research. Using a rigorous glaciological theory abiding the physics of ice flow based on measurements from satellites and other observations, they calculated the average snow line needed to bring the ice sheet back into balance. This average snowline increases the melt area resulting in increased imbalance and ultimately a slower alteration of the shape of the ice sheet. Now equivalent with losing an absolute minimum of 3.3 percent of total volume, equal to 110 trillion tonnes of ice or a sea level rise of 27 cm.

As a lower bound, the Greenland Ice Sheet is committed to lose 3.3 % of current mass possibly within this century. This corresponds to:

  • 110 trillion tonnes of ice (110,000,000,000,000 tonnes)
  • Covering the entire United States with 11 meters of water (37 feet)
Sea level rise minimum and likely