Greenland ice sheet melting rate is accelerating, scientists say – Science News


To say that it has been a bad year for the news on climate change is a euphemism.

Greenland Melting Key Points

Key points:

  • Greenland's melting rate was up to five times higher in the last 20 years than pre-industrial rates
  • Melting is following an exponential path where small increases in temperature are equivalent to much higher melt rates
  • The Greenland ice sheet contains enough water to raise sea level by 7 meters

Both the UN Environment Program and the Intergovernmental Panel on Climate Change (IPCC) sounded the alarm about the terrible climate we are in, and the enormous efforts needed to limit warming to 2 degrees Celsius above pre-industrial levels.

And in June, a study published in Nature pointed to a three-fold melting rate of the Antarctic ice sheet over the past five years.

Now a new research published in Nature today has confirmed that a similar trend is occurring in the Greenland ice sheet.

Researchers used ice cores to create a continuous 350-year analysis of the melting rate of ice in the Midwest of Greenland.

An ice core is a sample taken from an ice block with a hollow drill, revealing a cross section that effectively looks back in time, a bit like the rings of a tree.

They found that in the past 20 years the melt rate was five times higher than pre-industrial rates, and that the melting rate is increasing, according to researcher Luke Trusel of Rowan University in the United States. .

"The main conclusion we find is that it is now melting more in the last decades than at any other time in the last four centuries, and probably more than at any other time in the last seven to eight thousand years," Trusel said.

According to the ice core samples, 2012 was "unequivocally" the most intense year of melting recorded in Greenland.

An increase in the melting rate was detected in ice cores from the mid-nineteenth century, which occurred about the same time as the beginning of Arctic warming in the industrial era.

But it was only during the 1970s that the melting clearly violated the natural variation of variability.

In other words, we expect to see some differences in melting between the years, but during the 1970s this meltdown occurred on a scale beyond what could be explained by a fluctuation around a steady mean of ice cover.

More than 7 meters of sea level rise locked in the Greenland ice sheet

Significantly, they confirmed that the increasing fusion rate is following an exponential trajectory, caused by positive feedbacks like the albedo effect, according to Dr. Trusel.

The albedo effect describes the phenomenon in which dark surfaces absorb more heat than white reflective surfaces, such as ice and snow.

As the ice melts, darker soil absorbs more energy from the sun, which causes even more melting – creating a feedback loop.

"The response of the ice sheet to warmer weather is not linear," Trusel said.

"What that basically means is that, let's say we have half a degree of warming today, that would produce twice as much or more than half a degree of melting that occurred at some point in the past."

Most of the previous research has used satellite observations and computational modeling to calculate the fusion rate in Greenland.

This new research allowed scientists to cross their satellites' observations against physical ice cores, according to Dr. Trusel.

Being able to track 350-year melt rates is a particular strength of this latest survey, according to Matt King of UTAS who was not involved in this study.

"We did not have a general assessment, certainly coming back here almost until the time of Shakespeare," King said.

"From this kind of measure we can learn a lot about how quickly things are changing in Greenland."

And understanding how the ice sheet is melting fast is crucial in preparing for the impact of sea level rise in the future, according to Professor King.

According to this year's IPCC report, warming between 1.5C and 2C blocks Greenland's eventual total deglaciation.

This means that eventually the Greenland ice sheet will cause oceans around the world to increase by an average of more than 7 meters.

"So there are two questions: [and] Secondly, how fast is this [melting] will occur, "said Professor King.

"It may take thousands of years or hundreds of years and that's the kind of question we're trying to answer."

& # 39; Very unusual things are happening on this planet & # 39;

Although climate change has so far resulted in heating around 1 ° C on average from pre-industrial levels, this warming was not uniform.

In the Arctic and Greenland, heating signatures have been detected since the 18th century, and average summer temperatures have risen around 2C since the 1990s.

It is a process called polar amplification, and this means that small increases in global mean temperature will have the greatest effect on the polar regions.

And there are other positive feedbacks to consider as well.

Most of us know that when we climb a mountain, the temperature drops and vice versa.

Greenland's ice sheet is up to 3 kilometers thick in some places, but as it melts, the altitude of the surface layer is reduced.

In turn, the surface comes in contact with the warmer air and the melting increases.

The complexity of the ice melt and the potential of the planet to melt the Greenland ice sheet means that we need to seriously consider what impacts our actions will have today in the future, according to Dr. Trusel.

"We may think Greenland is remote and not very important, but when Greenland changes, it affects the world's coasts," said Trusel.

According to Professor King, this research is more of a year-long wake-up call alert.

"It reminds everyone in the global community once again that very unusual things are happening on this planet."

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