Greenland and Antarctica have lost 11,309 billion tonnes of ice between 1979 and 2023, raising sea levels by 31.4 mm; glaciers drive 84% of loss, surface melting 16%
Greenland and Antarctica have lost a combined 11.3 billion tonnes of ice since the late 1970s, contributing more than 3 centimetres to global sea level rise, according to a new international assessment by polar scientists.As per SWNS, the comprehensive study, led by researchers at Northumbria University and supported by NASA, provides what scientists describe as the most complete picture yet of how the world’s two major ice sheets have changed over the past half-century.Between 1979 and 2023, the Greenland and Antarctic ice sheets lost an estimated 11,309 billion tonnes of ice, raising global sea levels by 31.4 millimetres. Greenland accounted for the larger contribution, while Antarctica was responsible for 13.3 millimetres of sea level rise.
Glacier acceleration drives most of the ice loss
One of the study’s key findings is that the majority of ice loss was not caused by melting at the surface.Researchers found that around 84% of the ice loss occurred because glaciers accelerated and discharged more ice into the ocean, while surface melting accounted for approximately 16%.Dr Ines Otosaka, one of the study’s leads, said extending the record back to the 1970s has provided scientists with a clearer understanding of how the ice sheets have responded to a warming climate.“More than four-fifths of the ice lost was discharged into the ocean by faster-flowing glaciers, rather than melted at the surface,” Otosaka said. She added that the finding indicates the long-term trend is being driven by the “dynamic response of the ice sheets to a warming ocean.”The assessment brought together 42 independent satellite surveys from 27 satellite missions, using the early Landsat archive to extend observations back to 1972 for Greenland and 1979 for Antarctica.
Ice losses accelerated sharply from the 1990s
Faster-flowing glaciers accounted for 84% of the ice loss, scientists found. (Photo: SWNS)
The long-term record shows that ice losses increased substantially from the 1990s onwards.In Greenland, annual ice loss increased from around 60 billion tonnes in the 1980s to 264 billion tonnes in the 2010s. The latter decade was characterised by several extreme summer melt events.Antarctica also experienced a significant increase, with annual losses rising from approximately 48 billion tonnes in the 1980s to 202 billion tonnes in the 2010s.Together, the two ice sheets are now responsible for around a quarter of global sea level rise, according to the assessment.
Recent slowdown does not signal a reversal
The researchers noted that ice loss temporarily slowed between 2020 and 2023. However, they cautioned against interpreting the recent change as evidence that the longer-term trend has reversed.In Antarctica, unusually high snowfall over East Antarctica offset some of the ice being lost from glaciers in other parts of the continent. In Greenland, several relatively mild summers reduced surface melting, roughly halving the contribution from melt during the most recent period.Scientists described these developments as short-term fluctuations within a much longer pattern of ice loss.
Millions more people at risk from rising seas
Professor Andrew Shepherd, Head of the School of Geography and Natural Science at Northumbria University and a lead researcher on the assessment, highlighted the implications of the increase in sea levels for coastal communities.“Three centimetres of sea level rise may sound small, but that puts another six to nine million people at risk of coastal flooding and erosion,” Shepherd said.“With the ice sheets set to lose much more ice in the decades ahead, global assessments like IMBIE are vital to protecting communities impacted by climate change,” he added.The researchers say that maintaining a continuous record of ice-sheet behaviour is increasingly important as hundreds of millions of people live in low-lying coastal regions vulnerable to rising seas.
Satellite observations offer crucial evidence
Dr Tyler Sutterley, a co-lead on the assessment from the University of Washington Applied Physics Laboratory, said the latest study benefits from a longer observation record, participation from more research teams and improvements in measuring uncertainties.“The added length of the record, the larger pool of participating teams and our improved ability to assess uncertainties make this the most robust assessment of ice sheet mass balance produced so far,” Sutterley said.He added that satellite observations provide continent-wide evidence of changes occurring year after year, allowing scientists to test climate models and improve projections of future sea level rise.The researchers argue that the half-century record is particularly valuable because it captures how Greenland and Antarctica have responded to a warming climate over an extended period. They say these observations will be critical for understanding how ice-sheet changes could affect global sea levels and coastal communities in the decades ahead.
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