Scientists at Northumbria University in the UK have confirmed that Greenland’s ice sheet is melting at an alarming rate, with ice loss accelerating fivefold over the past thirteen years. Their research, published last December, used the first joint satellite measurements to track ice thinning, revealing serious implications for rising global sea levels.

The researchers at the UK Centre for Polar Observation and Modelling made the first direct comparison of ice thickness changes using two complementary satellite technologies: ESA’s CryoSat-2’s radar and NASA’s ICESat-2’s laser. The study also leveraged ESA’s 2020 Cryo2ice campaign, which aligned satellite orbits to enable simultaneous radar and laser observations, improving snow depth and ice volume measurements like never before. “Understanding the similarities and differences between radar and lidar ice sheet height measurements allows us to fully exploit the complementary nature of these satellite missions,” said Thorsten Markus, a project scientist for the ICESat-2 mission. The study found that both satellite systems came to the same conclusion of about a 3% change in ice volume, reinforcing confidence in the data and validating the alarming trend of ice loss.

Greenland’s ice sheet has played a critical role in stabilising global sea levels, as it holds 99% of Earth’s freshwater ice. The study confirms that between 2010 and 2023, the Greenland ice sheet lost 2,347 cubic kilometres of ice – an amount comparable to Lake Victoria in East Africa. The overall thinning averaged 1.2 meters, but the loss was significantly higher along the ice sheet’s outer edges (known as the ablation zone), which thinned by an average of 6.4 meters. The study identified extreme melting events in 2012 and 2019, where more than 400 cubic kilometres of ice was lost in each year due to record-breaking summer temperatures. If current trends persist, the Intergovernmental Panel on Climate Change estimates sea levels could rise by 148 to 272 millimetres, threatening coastal cities and ecosystems worldwide.

Previous estimates of Greenland ice thinning relied on singular data sources, but this study’s use of radar and laser measurements offers unprecedented accuracy. Radar technology can penetrate cloud cover but requires adjustments for ice surface penetration, whereas laser technology provides precise surface measurements but is blocked by clouds. The way both systems complement each other enhances confidence in the observed ice loss. “It is great to see that the data from ‘sister missions’ are providing a consistent picture of the changes going on in Greenland,” said Markus, underscoring the reliability of these findings. 

Beyond measuring surface of ice sheets, the study also provides critical insights into how ice sheets respond to changes in ice shelves. Glaciologist Matt King of the University of Tasmania highlighted that a key strength of this research is its ability to measure both grounded ice and land ice extending into the sea. Unlike previous studies, which focused on one or the other, this approach provides a more comprehensive understanding. “We know that ice on land responds to ice extending onto the sea, so looking at the ice sheet as a whole is an advance,” described King. Study co-author Helen Amanda Fricker of the University of California explained why this distinction is crucial for understanding future sea level rise. “Scientists need to know how ice sheets are changing if we are going to be able to predict how grounded ice might leave the Antarctic continent,” she added. Although floating ice shelves do not contribute directly to sea level rise, they act as stabilising barriers that slow glaciers from flowing into the ocean. “Knowing this won’t slow it down, but it will help us make informed decisions.”

The study underscores the necessity of continuous monitoring, as well as immediate policy action, to mitigate global warming. “This collaboration represents an exciting step forward, not just in terms of technology but in how we can better serve scientists and policymakers who rely on our data to understand and mitigate climate impacts,” said Tommaso Parrinello, the CryoSat-2 mission manager. Ultimately, this research reinforces the urgent need for decisive measures to curb greenhouse gas emissions and slow global temperature rise before irreversible damage occurs.