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Melting ice is responsible for a quarter of all sea level rise
The seven worst years in terms of polar ice sheet melting and ice loss have occurred in the last decade, with 2019 being the worst on record, according to new research. Melting ice sheets are now responsible for a quarter of all sea level rise - a fivefold increase since the 1990s - according to IMBIE, an international team of researchers that combined 50 satellite images of Antarctica and Greenland from 1992 to 2020. The findings are published today in the journal Earth System Science Data.
Global warming is melting the polar ice sheets, leading to rising sea levels and flooding along the coasts of our planet. Ice loss in 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) funded the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE) in 2011 to compile satellite records of polar ice sheet melting. The data collected by the team is widely used by leading organisations such as the Intergovernmental Panel on Climate Change (IPCC).
50 satellite images of Antarctica and Greenland were combined
In its latest assessment, the IMBIE team, led by the University of Northumbria's Centre for Polar Observation and Modelling, combined 50 satellite images of Antarctica and Greenland to determine their ice melt rates.
The scientists found that the Earth's polar ice sheets lost 7,560 billion tonnes of ice between 1992 and 2020 - the equivalent of an ice cube 20 kilometres high.
Overall, the polar ice sheets have lost ice in every year of the satellite records, and the seven years with the highest ice melt are in the last decade.
The satellite records show that 2019 was the year of record melt, with the ice sheets losing a staggering 612 billion tonnes of ice.
This loss was caused by a heatwave in the Arctic summer, which led to record melting in Greenland, which peaked at 444 billion tonnes this year. Antarctica lost 168 billion tonnes of ice - the sixth highest since records began - due to continued acceleration of glaciers in West Antarctica and record melt on the Antarctic Peninsula. The East Antarctic Ice Sheet remained nearly in equilibrium, as it has throughout the satellite era.
Melting of the polar ice sheets has led to a 21 mm rise in global sea level since 1992, of which almost two-thirds (13.5 mm) is due to Greenland and one-third (7.4 mm) to Antarctica.
Ice loss in Greenland and Antarctica has increased rapidly
In the early 1990s, ice sheet melt was responsible for only a small fraction (5.6%) of sea level rise. Since then, however, melting has increased fivefold, so that it is now responsible for more than a quarter (25.6%) of total sea level rise. If the ice sheets continue to lose mass at this rate, they will contribute between 148 and 272 mm to global mean sea level rise by the end of the century, according to the IPCC.
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're finally to the point where we can continuously update our estimates of ice sheet mass balance because there are enough satellites monitoring them in space, which means people can use our results immediately."
Dr Inès Otosaka from the University of Leeds, who led the study, said, "Ice loss in Greenland and Antarctica has increased rapidly over the satellite record and is now a major factor in sea level rise. Continued monitoring of the ice sheets is critical to predicting their future behaviour in a warming world and adapting to the associated risks that coastal communities around the world will face."
This is now the third ice loss assessment produced by the IMBIE team, thanks to continued collaboration between space agencies and the scientific community. The first and second assessments were published in 2012 and 2018/19 respectively.
In recent years, ESA and NASA have made great efforts to launch new satellite missions that can monitor the polar regions. The IMBIE project has used this to produce more regular updates, and for the first time it is now possible to record polar ice sheet losses every year.
This third assessment by the IMBIE team, funded by ESA and NASA, involved a team of 68 polar researchers from 41 international organisations using measurements from 17 satellite missions, including for the first time the GRACE-FO gravity mission. Importantly, records of ice loss in Antarctica and Greenland were reconciled using the same methods and for the same time period. The assessment is now updated annually to ensure that the scientific community has the very latest estimates of polar ice loss.
Dr Diego Fernandez, Head of ESA's Research and Development Department, said: "This is another milestone in the IMBIE initiative and an example of how scientists can coordinate their efforts to assess the evolution of ice sheets from space, providing unique and timely information on the extent and onset of change".
"The new annual assessments are a step forward in how IMBIE will help monitor these critical regions where variations have reached a level where abrupt changes can no longer be ruled out."
The study, titled Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020, was published in the journal Earth System Science Data, and the new dataset is publicly available on the British Antarctic Survey website.
Source
northumbria.ac.uk/../polar-ice-sheet-melting-records-have-toppled-during-the-past-decade