Greenland Ice Sheet is approaching a critical tipping point 

The Greenland Ice Sheet, a massive body of ice covering an area of 1.7 million square kilometers (660,200 square miles) in the Arctic, has the potential to raise global sea levels by about seven meters (23 feet) if it were to melt completely. 

Understanding the timeline and rate of this melting process is crucial for scientists, as it helps them predict and prepare for the potential impacts on coastal regions worldwide. However, determining the rate at which the ice sheet could melt has proven to be challenging due to the myriad of factors that influence it.

In a groundbreaking new study, climate scientist Dennis Höning from the Potsdam Institute for Climate Impact Research and his team have identified two critical tipping points that could determine the fate of the Greenland Ice Sheet. Tipping points are thresholds where a system’s behavior undergoes an irreversible change, and in this case, could lead to the permanent loss of large portions of the ice sheet. 

According to the study, published in AGU’s journal Geophysical Research Letters, if humanity releases 1,000 gigatons of carbon into the atmosphere, it will trigger the melting of the southern portion of the ice sheet. 

A more alarming tipping point of 2,500 gigatons of carbon would result in the near-total loss of the ice sheet. Currently, we have emitted about 500 gigatons of carbon, placing us halfway to the first tipping point.

“The first tipping point is not far from today’s climate conditions, so we’re in danger of crossing it,” said Höning. “Once we start sliding, we will fall off this cliff and cannot climb back up.”

Between 2003 and 2016, the Greenland Ice Sheet has already experienced significant melting, losing approximately 255 gigatons (billions of tons) of ice each year. A complex interplay of factors, including air and water temperature, ocean currents, precipitation, and others, influences the rate and location of ice loss. 

The difficulty in predicting how these factors interact, coupled with the long timescales needed to study such a massive ice sheet, has made it challenging for researchers to accurately forecast how the ice sheet might respond to various climate and carbon emissions scenarios.

Previous research suggested that global warming between one and three degrees Celsius (1.8 to 5.4 degrees Fahrenheit) could irreversibly lead to the melting of the Greenland Ice Sheet. However, this new study employed a more comprehensive model, combining a whole Earth system model that takes into account all key climate feedback processes with an ice sheet behavior model. 

The researchers conducted a series of 20,000-year-long simulations with carbon emissions ranging from 0 to 4,000 gigatons to identify the equilibrium states of the ice sheet and the critical tipping points.

As the ice sheet melts, its surface will be exposed to warmer air temperatures at lower elevations, creating a feedback loop that accelerates the melting process. Höning explains that a brief temperature increase of two degrees Celsius (3.6 degrees Fahrenheit) would not trigger this feedback loop, but maintaining elevated global air temperatures for hundreds of years or longer would. 

Once the ice sheet crosses the tipping point, its continued melting becomes inevitable, and even a reduction in atmospheric carbon dioxide to pre-industrial levels would not be sufficient to regrow the ice sheet significantly.

“We cannot continue carbon emissions at the same rate for much longer without risking crossing the tipping points,” Höning warned. “Most of the ice sheet melting won’t occur in the next decade, but it won’t be too long before we will not be able to work against it anymore.”

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