Ice sheet loss puts coastal communities at new risk

There have been new warnings of ongoing impact to the world’s sea levels as research has found the seven worst years for polar ice sheets melting and losing ice have occurred during the past decade.

According to scientists from the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE), the melting ice sheets now account for a quarter of all sea level rise – a fivefold increase since the 1990’s. The researchers combined 50 satellite surveys of Antarctica and Greenland taken between 1992 and 2020.

Global heating is melting the polar ice sheets, driving up sea levels and coastal flooding around our planet, researchers warned. Ice losses from Greenland and Antarctica can now be reliably measured from space by tracking changes in their volume, gravitational pull, or ice flow.

NASA and the European Space Agency (ESA) awarded funding to the IMBIE in 2011 to compile the satellite record of polar ice sheet melting. Data collected by the team is widely used by leading organisations, including by the Intergovernmental Panel on Climate Change (IPCC).

In their latest assessment, the IMBIE Team – which is led by Northumbria University’s Centre for Polar Observations and Modelling – found that Earth’s polar ice sheets lost 7,560 billion tonnes of ice between 1992 and 2020 – equivalent to an ice cube that would be 20 kilometres in height.

The polar ice sheets have together lost ice in every year of the satellite record, and the seven highest melting years have occurred in the past decade.

The satellite records show that 2019 was the record melting year when the ice sheets lost a staggering 612 billion tonnes of ice.

This loss was driven by an Arctic summer heatwave, which led to record melting from Greenland peaking at 444 billion tonnes that year. Antarctica lost 168 billion tonnes of ice – the sixth highest on record – due to the continued speedup of glaciers in West Antarctica and record melting from the Antarctic Peninsula. The East Antarctic Ice Sheet remained close to a state of balance, as it has throughout the satellite era.

Melting of the polar ice sheets has caused a 21 mm rise in global sea level since 1992, almost two thirds (13.5 mm) of which has originated from Greenland and one third (7.4 mm) from Antarctica.

In the early 1990s, ice sheet melting accounted for only a small fraction (5.6 %) of sea level rise. However, there has been a fivefold increase in melting since then, and they are now responsible for more than a quarter (25.6 %) of all sea level rise. If the ice sheets continue to lose mass at this pace, the IPCC predicts that they will contribute between 148 and 272 mm to global mean-sea level by the end of the century.

Professor Andrew Shepherd, head of the Department of Geography and Environmental Sciences at Northumbria University and founder of IMBIE, said: “After a decade of work we are finally at the stage where we can continuously update our assessments of ice sheet mass balance as there are enough satellites in space monitoring them, which means that people can make use of our findings immediately.”

Dr Inès Otosaka from the University of Leeds, who led the study, said: “Ice losses from Greenland and Antarctica have rapidly increased over the satellite record and are now a major contributor to sea level rise. Continuously monitoring the ice sheets is critical to predict their future behaviour in a warming world and adapt for the associated risks that coastal communities around the world will face.”