Environment

Greenland ice melt has already locked in 10 inches of sea level rise

Greenland ice melt has already locked in 10 inches of sea level rise
Ice melt in Greenland is a major contributor to sea level rise
Ice melt in Greenland is a major contributor to sea level rise
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Ice melt in Greenland is a major contributor to sea level rise
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Ice melt in Greenland is a major contributor to sea level rise
Diagram depicts this shifting snow line in Greenland
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Diagram depicts this shifting snow line in Greenland
Study author Jason Box in the field in Greenland
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Study author Jason Box in the field in Greenland
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As scientists sharpen their observational tools and more data comes to light, our view of the changes gripping our planet is only becoming clearer, and it's not a pretty sight. A striking new example of this has come from glaciologists studying the seasonal growth and loss of the Greenland Ice Sheet, who have concluded that even if we completely stopped burning fossil fuels today, it would shed enough mass on its own to cause global sea levels to rise by almost a foot, at a minimum.

Just as the Greenland Ice Sheet experiences melting in warmer weather, the colder months cause snow resting on top to turn into ice. In a stable climate, this process would play out in equilibrium, with the mass lost over summer regained during the winter. But with the planet growing hotter due to climate change, things are becoming increasing off balance.

To understand how this melting ice will impact sea levels around the world, scientists use computer models of ice flow and complex climate interactions. According to the authors of this new study, this approach has shortcomings in that they are imprecise and don't account for a number of factors scientists are observing in the field. These include more rain that is accelerating the melting of surface ice, an influx of tropical ocean currents into Greenland's fjords, and the darkening of the sheet surface that causes it to absorb more heat.

"We’re observing many emerging processes that the models don’t account for that increase the ice sheet’s vulnerability," study author Alun Hubbard, Professor of Glaciology at University of Tromsø, writes in an accompanying piece for The Conversation.

Study author Jason Box in the field in Greenland
Study author Jason Box in the field in Greenland

Hubbard and his colleagues have taken a different approach, and one that sidesteps computer models completely. The study is built on two decades of measurements from weather stations, satellite data on bare ice and surface mass, and a glaciological analysis technique known as volume-area power law scaling.

The team made assessments on the changing climate in the Arctic between 2000 and 2019, and how this is contributing to the imbalance in the ice sheet's losses and gains each year. They did this by focusing on the shifting snow line, the boundary between the areas of the Greenland Ice Sheet that are subjected to melting in the summer and those that are not. A particularly warm summer might drive this snow line to higher elevations, exposing more ice to melting conditions, while a colder winter might bring it back down again.

Diagram depicts this shifting snow line in Greenland
Diagram depicts this shifting snow line in Greenland

The scientists found that Greenland's ice sheet is now in such a state of disequilibrium, and has become so out of tune with the Arctic climate, that it won't be able to sustain its mass. For the physics to add up, the sheet is now destined to correct itself by shedding a further 3.3 percent of its volume. That's even if the world stopped burning fossil fuels today. This equates to 110 quadrillion tonnes of ice, enough to drive up average global sea levels by at least 27 cm (10 in).

"It is a very conservative rock-bottom minimum. Realistically, we will see this figure more than double within this century," said lead author Jason Box, from the National Geological Survey of Denmark and Greenland. “In the foreseeable scenario that global warming will only continue, the contribution of the Greenland Ice Sheet to sea level rise will only continue increasing. When we take the extreme melt year 2012 and take it as a hypothetical average constant climate later this century, the committed mass loss from the Greenland Ice Sheet more than doubles to 78 cm (30 in).”

According to the US National Ocean and Atmospheric Administration (NOAA), global sea levels have risen by 8-9 inches (21-24 cm) since 1880, and the rate of level rise is only accelerating. The idea that Greenland alone is already expected to contribute more than this, likely by the end of the century according to the study authors, is an ominous sign.

Rising sea levels are expected to bring a host of new dangers to coastal communities around the world. These include shoreline erosion, risks to wildlife and damage to infrastructure, from bridges to beachfront apartments. Higher background water levels would mean that destructive storm surges make their way further inland, while flooding would become far more frequent. According to NOAA, high-tide flooding along much of the US coastline is already 300-900% more frequent than it was just 50 years ago.

As we saw in another study this month highlighting the accelerated warming taking place in the Arctic, modern satellite data continues to shed important new light on the effects of climate change. In this case, the study authors see their new approach as a valuable way of filling in important blanks created by imperfect modeling.

"The ice flow models are not ready in this area," said Box. "This is a complimentary way of calculating mass loss that has been lacking."

The research was published in the journal Nature Climate Change

Source: National Geological Survey of Denmark and Greenland

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8 comments
8 comments
guzmanchinky
We should be building crazy nuclear and banning oil today, and yet we just party on...
David F
How much of the Greenland ice melt is due to atmospheric effects and how much due to heating from the mantle plume under Greenland.
Robt
@guzmanchinky But you may not have noticed that every country / state / politician that is wedded to a ‘green’ agenda has also demonised nuclear. See: Germany, Japan, California, New York etc. (Please don’t refer to very recent changes of heart as in the past few weeks)
Strange isn’t it? Do you think there’s an underlying agenda?
Ric
When are people going to realize that it’s already too little too late for decarbonization and that it MUST be supplemented with geoengineering. This is the only second chance we are going to get - too little geo-engineering too late does not allow for any third chances. Let’s trigger some volcanoes or spray some similar substance into the upper atmosphere to deflect some heat while we complete the decarbonization process. Melting of the ice caps and permafrost are past the point of no return.
History Nut
So the average level rises by about a foot? Guess I better keep my waders handy! Tidal surges are often multiple feet in change so seacoast people build accordingly. I don't believe that human technoligical development is having that great of an effect compared to the natural climate change that has occured since the Earth formed. My main concern with human-caused effect is with pollution. Clean water and air are critical. Ice Age bad, warming good. Maybe if the ice melts off Greenland it will live up to its name. As far as "flooding" coastal infrastructure, history shows that people have had to rebuild whole cities at higher levels due to rise of water levels. I applaud the researchers for accumulating data. Data is good, more data better. What we do with the data is sometimes sad. We should explore all technologies that decrease pollution while improving human existance but not get sidetracked by "chicken littles" screaming "the world is doomed unless we _________". Progress should be science/data based and will be gradual not sudden. Logic should be our rule, not emotional outbreaks of petty tyrants. We cannot 'save the Earth' because the Earth will always be here even if it is a lifeless, frozen rock. We can save human life by improving our civilization untill hopefully, we can live together without the constant urge to slit each others throats.
aksdad
They predict 274 ± 68 mm sea level rise (or more) just from Greenland ice melt by 2100. Measured average global sea level rise over the last 30 years is 3.3 ± 0.4 mm per year, approximately 330 to 370 mm higher in 2100 than in 2000, or about 13 to 14.6 inches. Either they're predicting that 83% to 92% of sea level rise will come from Greenland ice alone or they're way off. Based on the fact that they think their predictions align with the "unabated SSP58" scenario (essentially the RCP8.5 scenario) it's easy to see they are wildly off because most climate scientists acknowledge that RCP8.5 is probably unrealistic. In fact, actual measured warming and sea level rise falls squarely within the range of RCP2.6. But even if they're right, 274 to 342 mm of sea level rise means we're only a little closer to peak sea levels that were 4 to 6 meters higher 125,000 years ago during the previous interglacial warm period. At the rate we're going, it will be a couple thousand years or so before we get there.
Paul Anderson
Nuclear requires you to pay all the carbon costs upfront, or virtually all. Construction, mining and financing emission costs are all incurred decades before any “carbon-free” electricity can be generated. New nuclear adds to our current carbon emissions when what we need is immediate reductions. Nuclear is a poison pill…
Jeek
A question that everyone forgets to ask is this - Are polar ice caps normal? Evidence exists that Greenland and Antarctica were once tropical. Kansas was once under the sea.
So, if the ice caps are melting then it may be a return to normal conditions.