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Global warming led to frequent, extreme melting of ice in Greenland over past 40 years – Down To Earth Magazine

3.5 trillion tonnes of ice melted and flowed into the ocean over the past 10 years, raising sea levels and flood risk globally, according to a new study

Scientists, in a first-of-its-kind experiment, used satellite data to detect ice sheet runoff from space — and found that Greenland’s meltwater runoff rose by 21 per cent over the past four decades.

Over the past decade (2011-2020), increased melt-water runoff from Greenland raised the global sea level by one centimetre, according to a new research published in Nature Communications. A third of this total was produced in just two hot summers: 2012 and 2019.

Record levels of ice melted in the last 40 years: 3.5 trillion tonnes of ice melted and flowed into the ocean due to extreme weather.

Freshwater outflow and ice discharge from the ice sheet may become more variable and intense as the world gets warmer. This may have implications for ocean circulation and ecosystem productivity.

Thomas Slater, research fellow, Centre for Polar Observation and Modelling, University of Leeds, said:

As it gets warmer, it’s reasonable to expect that the instances of extreme melting in Greenland will happen more often. Observations such as these are an important step in helping us to improve climate models and better predict what will happen this century.

The study ‘Increased variability in Greenland Ice Sheet runoff from satellite observations’, used 51 million CryoSat-2 altimeter measurements acquired between January 2011 and October 2020.

The study was funded by the European Space Agency’s (ESA) part of its Polar+ Surface Mass Balance Feasibility project and used measurements from the ESA’s CryoSat-2 satellite mission.

The Greenland Ice Sheet has lost mass over recent decades because ice discharge has exceeded its surface mass balance. The mass loss has increased six-fold since the 1980s.

Surface mass balance is the difference between the precipitation (rain and snow) that has accumulated on the upper surfaces of glaciers and ice sheets and what has been lost due to melt and eventual runoff and evaporation. 

Hidden slabs of frozen meltwater has grown rapidly beneath Greenland’s surface since 2001 and the runoff from these ice slabs is set to contribute 7-33 millimetres and 17-74 mm to global sea level rise by 2100 under moderate to high emission scenarios respectively, a study in Nature dated September 19, 2019, said.

In August 2021, 7 billion tonnes of rain fell across Greenland across three days — the highest since records began in 1950. It is also the first time since then that rain, not snow, fell on Greenland’s highest peak.

This is disconcerting as any rain falling on Greenland’s surface speeds up melting. By August 15, the amount of ice lost was seven times greater than what is normal for mid-August.

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