Greenland 'zombie ice' an ominous warning for future, new study finds

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The Greenland ice sheet will lose at least 3.3% of its total mass in the coming years. (Baptiste Vandecrux, GEUS)

"Zombie ice" sounds like a very bad idea for a weather-themed horror movie, but it's real, and researchers have recently found that it's causing glaciers in Greenland to melt faster than experts previously predicted.

Scientists have known for years that sea levels are rising, but a new study published Monday in the journal Nature Climate Change shows that over time that rise could be at least 10 inches or more -- mainly because of what scientists are describing as zombie ice.

"It's dead ice. It's just going to melt and disappear from the ice sheet," study co-author William Colgan, a glaciologist at the Geological Survey of Denmark and Greenland (GEUS), told The Associated Press. "This ice has been consigned to the ocean, regardless of what climate (emissions) scenario we take now."

Researchers say to think of zombie ice as an "ice budget deficit" that occurs when glaciers stop receiving enough snow to replenish the ice already melting away each year. In an ideal situation, yearly snowfall would easily be able to compensate for the ice that naturally melts on the edges of glaciers, but emissions since at least the 1980s have made that impossible, the study says.


The study claims that 10 inches of ocean rise is inevitable, but it could be even worse -- up to 30 inches -- if preventative measures aren't taken. That's several orders of magnitude greater than the estimate from the Intergovernmental Panel on Climate Change (IPCC) of 2 to 5 inches by 2100. The absolute minimum ice loss means 120 trillion tons of water will melt off the Greenland ice sheet. That's enough to cover the entire United States in 37 feet of water, according to the AP.

Jason Box takes ice samples while standing on exposed ice below the snow line of the Greenland ice sheet. (GEUS)

"(Ten inches) is a very conservative rock-bottom minimum. Realistically, we will see this figure more than double within this century," lead author of the study Jason Box from GEUS said in a press release. As the climate continues to change and the ice sheet keeps melting, its impact on sea levels will only go up.

According to the National Aeronautics and Space Administration (NASA), glaciers in northwestern Greenland have been losing about 4 to 8 billion tons of ice per year in recent decades amid accelerated warming. That's more than the peripheral glaciers in southeastern and southwestern Greenland are losing, but less than in northern Greenland, where peripheral glaciers have been losing as much as 29 billion tons per year since the early 2000s.

The Helheim Glacier, on the southeast edge of Greenland, is one of the hardest-hit areas of the country by climate change. It shrunk about 6 miles in area between 2005 and 2019, meaning the ice pack that formed thousands of years ago simply dissolved into the sea. According to the AP, about 440 billion tons of ice melted or fell off the glacier in 2019, enough to flood Pennsylvania with a foot of water.

"If you look at climate model projections, we can expect to see larger areas of the ice sheet experiencing melt for longer durations of the year and greater mass loss going forward," University of Georgia ice scientist Tom Mote told AP. "There's every reason to believe that years that look like this will become more common."

However, an important aspect of this new study is that it's based entirely on real-world, recorded measurements, not simulations or computer models that tend to have a high degree of uncertainty. Over the last 20 years, researchers combined satellite measurements with visits to the glaciers to make their own recordings. The only catch with this method is that it lacks a specific timeframe. Whether that 10 inches of sea level rise will happen by 2100 or 2200, or somewhere in the middle, is currently unknown.

The research team sets up an automatic weather station on the snowy surface above the snow line in Greenland. (GEUS)

"In order to get the figure that we have, we had to let go of the time factor in the calculation," Box said. "But our observations suggest that most of the committed sea level rise will occur this century."

The study also considers only the melting in Greenland and does not factor in melting from any other ice sheets like Antarctica. That may not matter much, because even using the data from this study alone, Box said the severity of the melting zombie ice is like having "one foot in the grave."

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