Environment

Melting Greenland ice sheet has already passed major tipping point

Melting Greenland ice sheet ha...
An aerial view of Greenland, where melting glaciers are shrinking faster than they can be replenished
An aerial view of Greenland, where melting glaciers are shrinking faster than they can be replenished
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An aerial view of Greenland, where melting glaciers are shrinking faster than they can be replenished
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An aerial view of Greenland, where melting glaciers are shrinking faster than they can be replenished
Graph depicting ice loss in Greenland since 1985
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Graph depicting ice loss in Greenland since 1985

The yearly formation and shrinkage of the Greenland ice sheet is a delicate balancing act, with melting glaciers reducing its mass each summer before the snowfall replenishes it in the winter. New analysis of satellite data has revealed that these opposing forces are no longer working in harmony and the ice sheet is now shrinking so much that, even if climate change were to halt tomorrow, it has already passed a point of no return and would continue to shrink for some time.

The dire findings come from a team at the Ohio State University, who drew on nearly 40 years of satellite data to track changes in the Greenland ice sheet. This was made up of monthly data on more than 200 glaciers that drain away into the surrounding oceans, offering the scientists a look at long-term trends around ice loss and reformation through snowfall.

“We’ve been looking at these remote sensing observations to study how ice discharge and accumulation have varied,” says Michalea King, lead author of the study and a researcher at Ohio State University’s Byrd Polar and Climate Research Center. “And what we’ve found is that the ice that’s discharging into the ocean is far surpassing the snow that’s accumulating on the surface of the ice sheet.”

The data revealed that throughout the 80s and 90s, the balance between snowfall and ice loss was more or less sustainable, with the sheet shedding about 450 gigatons each year before regaining it through snowfall. However, the team found that around the turn of the century the ice loss started to pick up, with the glaciers losing around 500 gigatons each year while snowfall remained the same.

Graph depicting ice loss in Greenland since 1985
Graph depicting ice loss in Greenland since 1985

This differential over the past 15 to 20 years has now pushed the ice sheet past the point of no return, according to the scientists. They report that the large glaciers have retreated by an average of 3 km (1.86 mi) since 1985, with many of them now sitting in deep water that makes them more susceptible to melting, only compounding the problem.

Prior to 2000, the team says that the ice sheet had a 50-50 chance of either gaining or losing mass each year. In the current conditions, they expect it to gain mass only once in 100 years. Moreover, the researchers say that even if we were to somehow stop the process of climate change today, ice loss would continue to outstrip ice accumulation each year.

“Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss,” says Ian Howat, a co-author on the paper. “Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass.”

The findings are just the latest in a series of grim observations concerning the ice sheet and rising sea levels, of which Greenland’s melting glaciers are a big contributor. One paper published back in April revealed that the Greenland ice sheet lost 600 gigatons of mass in 2019, the biggest drop since records began in 1948. But as King points out, there are positives to come from these findings, in that they help us grasp the true reality of the problem at hand.

“It’s always a positive thing to learn more about glacier environments, because we can only improve our predictions for how rapidly things will change in the future,” she says. “And that can only help us with adaptation and mitigation strategies. The more we know, the better we can prepare.”

The research was published in the journal Communications Earth and Environment.

Source: Ohio State University

11 comments
Worzel
That means that Greenland may soon be back to the same state it was in, about 1000 years ago, so why the, ''The dire findings........!''?
Chris Coles
During 2012 I wrote a paper titled The Arctic Ice is Melting, We Must Face facts and distributed it to the UK government and my local County Council, Hampshire. As a corollary, I added this:
A short note to add some new thinking to the energy inputs influencing the formation of the Peterman Glacier Ice Tongue.
During the Greenland Ice Sheet melting season of roughly 30 days a very large proportion of the 1.7KM 3 of upper surface melt water flows down from the surface to the glacier base via Moulins. The Peterman Glacier drains 6% of the total ice sheet. The ice sheet is up to 3,000m thick but for this debate I am assuming the maximum height of the Moulins is 2,000m AMSL. During the melt season, there will be a flow of melt water, from Moulins into the Peterman Glacier of 39,352 Litres per second from a hydraulic head of 2,000m which gives an energy input of 770MW/s or 2.78TW/hr. An ice melt flow of this magnitude will create a massive exit plume under the glacier at the grounding line and will add to the energy input eroding the glacier. I present an illustrated description of the likely result and discuss some of the further implications.

Discussion.
What struck me was that it seems everyone is thinking drain pipes, rather than a fully enclosed hydraulic system; when they stand beside a Moulin at the upper surface of the Greenland Ice Sheet. Whereas they should recognise that they are standing upon perhaps the largest, most powerful hydraulic system, in the Northern hemisphere. That flow of liquid water immediately carries kinetic energy from the moment it starts its downward journey and it cannot lose it until it ceases motion; while imparting that energy to the surrounding mass of the ice sheet. Another aspect is that water under pressure carries heat much more efficiently than water at ambient pressure; a point long exploited by industrial heating systems based upon high temperature water as the heat exchange medium. So the energy input from the water column, both as a pressurised hydraulic medium and as a kinetic energy flow may be very substantial indeed. Then add another energy input. All atmospheric columns, such as a 3,000m high Moulin tube, have to obey adiabatic lapse rate rules. The Adiabatic Lapse Rate is 2.7 degrees C per 300m. Now, normally, this is associated with the temperature DECREASING as you climb up through the atmosphere from the surface. But again, it seems everyone has missed the simple fact that, if the temperature of the atmosphere at the upper surface of the Greenland Ice Sheet, at say, 3,000m AMSL, is above freezing, say + 3 degrees C, then the same rules apply in reverse. That seemingly empty Moulin is delivering energy at its base relative to the lapse rate in reverse; from top to bottom of the ice sheet; right through the entire column of the ice sheet within every Moulin. Taking all these additional suggestions together, it seems to me that a careful revision of the underlying thinking contained in the paper titled: Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow, H.Jay Zwally, et al. will reach a conclusion that they were right to ask their questions and indeed; that they have substantially underestimated their conclusions. This is inevitably a very brief note to illustrate my thinking. I also have some ideas of how to design and construct a submersible vehicle that might make it possible to view the complete length of the underside of the Peterman Glacier Tongue to confirm the mechanisms involved. But that would require funding. As a first thought, I suggest that you place a seismometer above the Peterman Glacier grounding line just before the next melt season. Indeed an boxed array of several would be better, as well as a very accurate GPS which should show that the glacier will lift slightly as the melt water flow commences. Chris Coles September 23, 2012.

My suggestions have it would seem been taken up by others. My main point is that if these figures are any way near correct, the real danger is the erosion of the base of the Greenland ice sheet, which has to support the entire load of what is, at up to 3KMs thick; the largest block of ice on the surface of the planet. That there may be a real danger of the total sudden collapse of the entire block of ice due to the area at the base being unable to support the full load; always remembering that ice skates slide because the weight of your body melts the ice under the slim skate. If the surface area at the base of the ice reduces to a point where the load above will start to melt the base; then we may experience a acceleration of such melting. Food for thought?
Mike Johnson
If we are entering into one of the occasional warming periods this might provide optimal conditions for Human Civilization. All changes are not automatically apocalyptic grim disasters though this coding does sell much better than any sort of thoughtful approach.
Catweazle
As is only to be expected as the World warms up from the last Ice Age. So why the panic?
Adrian Akau
India has borrowed 500 million from the US to improve transport between the Maldives islands. The average height above ocean level there is 59 inches. It is predicted that ocean height will increase 29 inches by 2100 which means that many of the 350,000 or so inhabitants will have to be re-located.
Bruce H. Anderson
Using 40 years of data may make for a long-term trend in some fields, but the overall climate is measured in millennia at best.
Lumir Janku
@Catweazle "As is only to be expected as the World warms up from the last Ice Age. So why the panic?"

1) We are still in an Ice Age.
2) Interglacials (like our Holocene) tend to spike at their end towards hotter climate before the plunge. In average, they last 7k-10k years. We'v e been lucky with nearing 12k. Perhaps it is because there has been a short lasting reversal back to near glacial climate at a 11ky boundary. However, our interglacial may not last and another glacial lasting 80k to 120k may lie in wait before our gates.

@Worzel Greenland was named as such during MWP (Medieval Warm Period). By the onset of the 14th century, even Iceland was better off.
Robert in Vancouver
We have gone way past at least 20 tipping points. We were all supposed to be dead from global warming heat waves many years ago.

Now that covid-19 is losing some of it's scare factor, we will be seeing more global warming headlines again.

Oh sorry, I meant to say Climate Change headlines. Or should I say global cooling as it was called it in the 1970's.
Johannes
Personally Worzel, I don't want to live in the world of 1000 years ago - I'd be dead by now. Read some history.
Pmeon
It is called Greenland not Whiteland for a reason.