Greenland Melt Strong, Accelerating

January 22, 2019

Latest in a recent slew of papers confirming increasing mass loss on Greenland ice sheet – I spoke to Luke Trusel, whose paper in Nature last month has been  widely cited, last month in Washington DC.

In 2012, we saw the culmination of 2 decades of strong warming on the Greenland sheet, with a surface melt event that extended over the whole of the island, and a record mass loss.

In 2013, which was the first year I went to Greenland with Dark Snow Project, we saw cooler temperatures, and the beginning of a “pause” in the melt, which some scientists have ascribed to a phase shift of the North Atlantic Oscillation.
A new paper deals with this.
Spoiler: Melting continues.

NYTimes:

Greenland’s enormous ice sheet is melting at such an accelerated rate that it may have reached a “tipping point,” and could become a major factor in sea-level rise around the world within two decades, scientists said in a study published on Monday.

The Arctic is warming at twice the average rate of the rest of the planet, and the new research adds to the evidence that the ice loss in Greenland, which lies mainly above the Arctic Circle, is speeding up as the warming increases. The authors found that ice loss in 2012, more than 400 billion tons per year, was nearly four times the rate in 2003. After a lull in 2013-14, losses have resumed.

The researchers tied the pause in melting to a reversal of the cyclical weather phenomenon known as the North Atlantic Oscillation. Before the pause, the oscillation was in what is known as its negative phase, which is associated with warmer air hitting west Greenland, along with less snowfall and more sunlight, all of which contribute to ice loss. When the cycle shifted into a positive phase in 2013, an “abrupt slowdown” of melting occurred.

Yet, the slowdown was anything but good news, said Michael Bevis, the lead author of the paper and a professor in the School of Earth Sciences at Ohio State University.

The North Atlantic Oscillation has occurred throughout the historical record, he noted. But before 2000, overall average temperatures were cool enough that the N.A.O.’s positive and negative cycles did not have much of an effect on rates of melting in Greenland.

Now, the strong effect that the cooler cycle had on the rate of melting — even if it was helpful in stopping ice loss — is a reason for concern, Dr. Bevis said. If the warm cycles of the N.A.O. are associated with huge losses of ice, and the cool cycles only pause the melting, it suggests a threshold has been reached: As average temperatures rise further, melting will be more sustained, and the cooling cycles will have less of an effect in slowing the ice loss.

“If a relatively minor cycle can cause massive melting,” he said, “it means you’ve reached a point of amazing sensitivity” to warmer temperatures, which could represent “the tipping point.”

And so, he said, “One degree of warming in the future will have way more impact than one degree of warming in the last century.”

The new research dovetails with other recent papers on the accelerating melting. Last month a team of researchers published a paper in Nature that used satellite observations, analysis of ice cores and models to show that losses from the Greenland ice sheet have reached their fastest rate in at least 350 years.

Luke D. Trusel, a glaciologist at Rowan University and an author of last month’s Nature paper on Greenland, said the new research by Dr. Bevis and his colleagues “provides clear and further illustration of how sensitive Greenland now is” to global warming.

“What’s happening today is well beyond the range of what could be expected naturally,” he said. “The human fingerprint on Greenland melting today is unequivocal.”

Time:

These grim conclusions came in the wake of a separate study last week that made similar warnings about Antarctica. Scientists from the University of California, Irving and Utretcht University in the Netherlands found that Antarctic ice loss has also rapidly accelerated over the past four decades, from about 40 billion tons per year in the 1980s, to over 250 billion tons per year from 2009–2017.

Scientists have warned that Antarctic ice melt could raise global sea levels 3.5 feet by 2100 unless urgent action is taken to limit greenhouse gas emissions.

 

 

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7 Responses to “Greenland Melt Strong, Accelerating”

  1. indy222 Says:

    Hansen in 2016’s paper found ice loss could be characterized quite plausibly by a doubling time of 10-20 years. This new paper says yes; exponential decline, and the doubling time is only 7.5 years.

    Are we getting a sick pit of fear in the middle of the stomach now?

    • dumboldguy Says:

      I’ve had a “sick pit of fear” in both my stomach and my head ever since I heard the terms “positive feedback”, “exponential”, and especially “tipping points” many years ago.

      All these “revelations” that have come out in various studies and reports over the past two months have only made things worse. Grim news indeed.

      • Paul Whyte Says:

        I had a “sick pit of fear” in 1980 when I expressed a liking of the environment and dislike of an extreme right-wing politician to my research funders – a petrol company who wanted to sell petrol for the next 200 years. I lost my funding that minute.

        I was investigating hydrotreating heavy oil so it could be used for refinery feedstock when the light ran out. Yes, it was obvious then that the Keeling curve would go the way it has and that temperatures would follow.

        In 1975 in Chemistry II the basics of climate science were explained and the effects with the need to move away from carbon as the primary energy source. It was also explained that the student’s generation would have to do it.

        While I had thought that everyone would just sensibly move away from carbon once its effects could be seen on the temperature record. The OMG moment was when I could tell that the petrol companies had dug in.

  2. grindupbaker Says:

    It was always obvious that ice melts exponentially, not linearly. I’ve lived in Canada 46 years and I’ve seen ice melt in spring, it melts exponentially.

  3. Keith McClary Says:

    “Researchers calculate decades of ‘scary’ Greenland ice melting”

    https://phys.org/news/2019-04-decades-scary-greenland-ice.html

    “Ice is melting six times faster than in the 1980s, researchers estimate—and Greenland’s glaciers alone have contributed to a 13.7 millimeter rise in sea levels since 1972, they believe.”


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