Greenland and Antarctica have lost 11.3 trillion tonnes of ice over the past 50 years, pushing global sea levels up by more than 1.1 inches (3cm), according to a new study by an international team of polar scientists.
The research team produced what it describes as the most complete picture yet of ice loss from the two largest ice sheets on the planet. Melting in Greenland has driven sea levels up by 0.7 inches (1.8cm), while Antarctica has contributed 0.5 inches (1.3cm) since 1976, the findings show.
Overall, 84 per cent of the combined ice loss was caused by glaciers speeding up and discharging more ice into the ocean, with just 16 per cent due to surface melting.
Dr Ines Otosaka of Northumbria University, the study's lead author, said reaching back to the 1970s allowed researchers to see how the ice sheets have changed across half a century. She said more than four-fifths of the ice lost was discharged into the ocean by faster-flowing glaciers rather than melted at the surface, which shows the long-term trend is being driven by the dynamic response of the ice sheets to a warming ocean.
How the data was gathered
For the study, researchers combined 42 independent satellite surveys, drawing on data from 27 satellite missions dating back to the 1970s. In total, Greenland and Antarctica lost 11,309 billion tonnes of ice between 1979 and 2023, with losses climbing steeply in recent decades.
Greenland's rate of loss rose from around 60 billion tonnes a year in the 1980s to 264 billion tonnes a year in the 2010s, a decade marked by repeated extreme summer melt events. Antarctica's rate rose from about 48 billion tonnes a year in the 1980s to 202 billion tonnes a year in the 2010s, with all of that loss caused by ocean melting of its outlet glaciers.
The study found that the most recent years, 2020 to 2023, brought a temporary slowdown in ice loss. Record snowfall over East Antarctica helped offset some of the continent's glacier losses elsewhere, while a run of milder Greenland summers roughly halved its surface melting. The scientists cautioned that these are short-term fluctuations against a clear long-term trend, not a reversal of ice loss.
Millions at risk of flooding
Professor Andrew Shepherd, who also led the study, said three centimetres of sea level rise may sound small, but it puts another six to nine million people at risk of coastal flooding and erosion. He said that with the ice sheets set to lose much more ice in the decades ahead, global assessments like this one are vital to protecting communities affected by climate change.
The findings, published in the journal Scientific Data, also underline the central role the ice sheets play in future sea level rise, the researchers said, since their response to a warming climate is the single largest source of uncertainty in sea level projections.
Globally, average sea level has risen by 0.14 inches (3.64 millimetres) a year since 1999, for a total of 3.6 inches (9.38cm) over the past 26 years. About 30 per cent of that increase comes from the ocean expanding as it warms, while the remaining 70 per cent mainly comes from melting glaciers and ice sheets. While the trend has been relatively stable for decades, recent satellite data shows it accelerated rapidly after 2012, jumping to 4.1mm a year.
Dr Diego Fernandez, head of the Science Section at the European Space Agency, said the findings show the fundamental importance of using satellites to monitor the ice sheets and evaluate the models used to predict the effects of climate change. He said sustaining missions such as CryoSat-2 and the Sentinels, and maintaining the long-term ice-sheet climate data record, is critical for the decades ahead.
UK homes at risk by 2300
A separate study warned that rising sea levels could plunge 1.7 million British homes underwater by 2300 and render parts of the UK uninhabitable. Researchers from the Met Office and the University of Bristol used computer models to assess how many people will be at risk of coastal flooding as a result of future climate change.
They found areas such as the Wash and the Humber Estuary stood out as hot spots for future coastal flooding. Large parts of the southeast, Norfolk, and the northwest coastline would also be submerged, with extensive flooding likely around Blackpool and Liverpool from the River Mersey. Densely populated cities would also bear the brunt, with a significant chunk of west London submerged by rising sea levels.
Professor Jeffrey Neal of the University of Bristol, a co-author of that study, said the worst-case sea level rise outcomes would pose massive challenges for the UK in the coming centuries, including the need for large-scale movement of populations and settlements away from the coast.
