Accelerated melt of ice sheets now unmistakable

From The BBC

If you could shape an ice cube out of all the ice losses from Greenland and Antarctica over the past three decades, it would stand 20km high.

An international group of scientists who work with satellite data say the acceleration in the melting of Earth's ice sheets is now unmistakable.

They calculate the planet's frozen poles lost 7,560 billion tonnes in mass between 1992 and 2022.

Seven of the worst melting years have occurred in the past decade.

Mass loss from Greenland and Antarctica is now responsible for a quarter of all sea-level rise.

This contribution is five times what it was 30 years ago.

The latest assessment comes from the Ice Sheet Mass Balance Intercomparison Exercise, or Imbie.

This project, which is supported by the US and European space agencies, issues regular reviews of the state of the planet's ice sheets.

This is the third such report, and like the previous studies, it has collated and reviewed all available satellite measurements.

It includes the observations from orbit of some 50 spacecraft missions from 1992. That particular year was when orbiting instruments best suited to studying the elevation and velocity of ice started overflying the poles routinely.

The 7,560 billion tonnes of ice lost from Greenland and Antarctica during the study period pushed up sea-levels by 21mm.

Almost two-thirds (13.5mm) of this was due to melting in Greenland; one-third (7.4mm) was the result of melting in Antarctica.

"All this has profound implications for coastal communities around the world and their risk of being exposed to flooding and erosion," said Dr Inès Otosaka from the UK's Centre for Polar Observation and Modelling (CPOM), who led the latest assessment.

"It's really important that we have robust estimates for the future contribution to sea-level rise from the ice sheets so that we can go to these communities and say, 'Yes, we understand what is happening and we can now start to plan mitigations'," she told BBC News.

Warmer air is melting the top of the Greenland Ice Sheet (NASA/GODDARD/MARIA-JOSÉ VIÑAS)