Once we emit about 1000 gigatons of carbon, much of the massive ice sheet will melt irreversibly. We’ve emitted 500 gigatons so far.
The Greenland Ice Sheet covers 1.7 million square kilometers (660,200 square miles) in the Arctic. If it melts entirely, global sea level would rise about 7 meters (23 feet), but scientists aren’t sure how quickly the ice sheet could melt. Modeling tipping points, which are critical thresholds where a system behavior irreversibly changes, helps researchers find out when that melt might occur.
Based in part on carbon emissions, a new study using simulations identified two tipping points for the Greenland Ice Sheet: releasing 1000 gigatons of carbon into the atmosphere will cause the southern portion of the ice sheet to melt; about 2500 gigatons of carbon means permanent loss of nearly the entire ice sheet.
Having emitted about 500 gigatons of carbon, we’re about 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 Dennis Höning, a climate scientist at the Potsdam Institute for Climate Impact Research who led the study. “Once we start sliding, we will fall off this cliff and cannot climb back up.”
The study was published in AGU’s journal Geophysical Research Letters, which publishes short-format, high-impact research spanning the Earth and space sciences.
The Greenland Ice Sheet is already melting; between 2003 and 2016, it lost about 255 gigatons (billions of tons) of ice each year. Much of the melt to date has been in the southern part of the ice sheet. Air and water temperature, ocean currents, precipitation, and other factors all determine how quickly the ice sheet melts and where it loses ice.
The complexity of how those factors influence each other, along with the long timescales scientists need to consider for melting an ice sheet of this size, make it difficult to predict how the ice sheet will respond to different climate and carbon emissions scenarios.
Previous research identified global warming of between 1 degree to 3 degrees
“We cannot continue carbon emissions at the same rate for much longer without risking crossing the tipping points,” Höning said. “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.”
Reference: “Multistability and Transient Response of the Greenland Ice Sheet to Anthropogenic CO2 Emissions” by Dennis Höning, Matteo Willeit, Reinhard Calov, Volker Klemann, Meike Bagge and Andrey Ganopolski, 27 March 2023, Geophysical Research Letters.
DOI: 10.1029/2022GL101827