7 worst years for polar ice sheet melting occurred over past decade: Study

New Delhi: Scientists report that the seven worst years for polar ice sheets melting and losing ice have occurred during the past decade with 2019 being the worst year on record.

Combining 50 satellite surveys of Antarctica and Greenland taken between 1992 and 2020, the international team of researchers have found that the melting ice sheets now account for a quarter of all sea level rise, a fivefold increase since the 1990's.

The team was led by Northumbria University's Centre for Polar Observations and Modelling, UK, and their findings are published today in the journal Earth System Science Data.

In their study, the researchers have found that Earth's polar ice sheets lost 7,560 billion tonnes of ice between 1992 and 2020, which is equivalent to an ice cube that would be 20 kilometres in height.

They also found that 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 showed that 2019 was the record melting year when the ice sheets lost a staggering 612 billion tonnes of ice.

They said that the loss, driven by an Arctic summer heatwave, led to record melting from Greenland peaking at 444 billion tonnes that year.

Antarctica was found to have 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 was found to remain close to a state of balance, as it had throughout the satellite era.

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

The researchers say that there has been a fivefold increase in melting since the early 1990's. While ice sheet melting accounted for only a small fraction, 5.6 per cent, of sea level rise then, they are now responsible for more than a quarter, 25.6 per cent, of all sea level rise.

If the ice sheets continue to lose mass at this pace, the Intergovernmental Panel on Climate Change (IPCC) has predicted their contribution to be between 148 and 272 mm to global mean-sea level by the end of the century.

"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," said Andrew Shepherd, professor and Head of the Department of Geography and Environmental Sciences at Northumbria University.

"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," said lead researcher Ines Otosaka from the University of Leeds.