A recent study has uncovered that the Greenland ice cap is losing an average of 30 million tonnes of ice per hour due to the climate crisis, which is 20% more than previously estimated. Concerns are rising among scientists about the additional freshwater entering the north Atlantic, as it could hasten the collapse of the Atlantic meridional overturning circulation (Amoc), potentially leading to severe consequences for humanity.
Traditional methods of measuring ice loss, such as assessing the ice sheet’s height or weight via gravity data, have been effective in determining losses that contribute to rising sea levels. However, these methods fail to account for the retreat of glaciers situated mostly below sea level in narrow fjords around Greenland. The recent study employed satellite photos analyzed by scientists to track the end position of Greenland’s numerous glaciers monthly from 1985 to 2022, revealing substantial and widespread shortening amounting to a trillion tonnes of lost ice.
Dr. Chad Greene from NASA’s Jet Propulsion Laboratory, leading the research, emphasized the significant and widespread changes occurring around Greenland, with nearly every glacier retreating over the past few decades. The study suggests that dumping freshwater into the north Atlantic weakens the Amoc, though the extent of weakening remains uncertain.
The Amoc, already at its weakest in 1,600 years, exhibited warning signs of a tipping point in 2021, with a potential collapse projected as early as 2025 in the worst-case scenario. Some parts of the Greenland ice sheet are also approaching a tipping point of irreversible melting, contributing to an expected sea level rise of 1-2 meters.
The study, utilizing artificial intelligence techniques, mapped over 235,000 glacier end positions from 1985 to 2022, revealing a loss of about 5,000 sq km of ice at Greenland’s margins, equivalent to a trillion tonnes of ice. The findings supplement existing measurements, with an additional 43 billion tonnes of ice loss per year, bringing the total to approximately 30 million tonnes per hour on average.
Scientists express concerns about any freshwater source potentially acting as a tipping point for a full-scale Amoc collapse, disrupting global weather patterns, ecosystems, and food security. However, current oceanographic models do not incorporate freshwater from Greenland’s glacier retreat. The influx of less dense freshwater into the sea slows the usual sinking of heavier salty water, impacting the Amoc.
Prof. Tim Lenton from the University of Exeter highlights the concern over additional freshwater input to the north Atlantic, especially in regions prone to collapse. The implications could include disruptions to weather patterns in the UK, western Europe, parts of North America, and the Sahel region.
While the pace of ice loss has been steady since the turn of the century, Prof. Andrew Shepherd at the University of Northumbria reassures that it remains below levels needed to disturb the Amoc. The discovery of extra ice loss is crucial for calculating Earth’s energy imbalance, providing insights into how much additional solar heat the Earth is trapping due to human-caused greenhouse gas emissions. Greene notes that the indirect effects of glacier retreat, such as allowing glaciers to speed up, could impact sea levels.
