Sea-level Rise: Greenland and the Collapse of the East Antarctic Ice Sheet

"Major sea-level rise caused by melting of Greenland ice cap is 'now inevitable'"

In 1995, I was convinced climate change was happening at an exponential rate; however, Sidd said we need more data over a longer time period. (The consensus at the time being global warming was linear, and we had thousands of years to solve the problem.)

It took until 2004 for Sidd to collect enough data. Indeed, we were convinced... using sea level rise and Greenland's ice sheets. My interest in sea-level rise and ice sheets collapsing began in the 1990's after I asked Sidd his greatest concerns about human induced climate change. Much of climate change can be reversed or at least stopped from worsening. The collapse of ice sheets is irreversible. Sidd said, "A terrible future awaited."

"I do hope I will succeed in illuminating the darker corners. And perhaps persuade some that effort is well expended in learning these complicated matters. I shall only touch on one very specific issue, that of sea level rise. Other large and looming problems such as the acidification of oceans, or large scale changes in precipitation are ignored in this essay, although I have investigated some of those issues, and I am quite concerned about them."

"And once we have destabilized these ice sheets, there will be no stable coastline for centuries. I repeat: There will be no stable coastline for centuries."

Greenland ice sheet climate disequilibrium and committed sea-level rise
A new study has been published showing that even if we stopped greenhouse gas emissions today, Greenland's ice sheet would continue to melt raising the sea level by at least 27 centimeters.

The Guardian reported:
"It is a very conservative rock-bottom minimum," said Prof Jason Box from the National Geological Survey of Denmark and Greenland (Geus), who led the research. "Realistically, we will see this figure more than double within this century."

"The minimum of 27cm is the sea-level rise deficit that we have accrued to date and it's going to get paid out, no matter what we do going forward," said Dr. William Colgan, also at Geus. "Whether it's coming in 100 years or 150 years, it's coming. And the sea-level rise we are committed to is growing at present, because of the climate trajectory we're on."

Colgan said: "If [2012] becomes a normal year, then the committed loss grows to 78cm, which is staggering, and the fact that we're already flickering into that range [of ice loss] is shocking. But the difference between 78cm and 27cm highlights the [difference] that can be made through implementing the Paris agreement. There is still a lot of room to minimise the damage."

"There is growing support in the scientific literature for multi-metre levels of rise within the next 100 to 200 years," said Colgan. A collapse of the colossal east Antarctic ice sheet, which would lead to a 52-metre rise in sea levels if it all melted, could be averted if rapid climate action is taken.

Prof. Gail Whiteman, at the University of Exeter, who was not part of the study team, said: "The results of this new study are hard to ignore for all business leaders and politicians concerned about the future of humanity. It is bad news for the nearly 600 million people that live in coastal zones worldwide. As sea levels rise, they will be increasingly vulnerable, and it threatens approximately $1tn of global wealth." She said political leaders must rapidly scale up funding for climate adaptation and damage.

Read the report from the journal Nature Climate Change: Greenland ice sheet climate disequilibrium and committed sea-level rise

The reason I'm making a big deal about this is -- Greenland is the canary in the coal mine for the collapse of the east Antarctic ice sheet. As an indicator, Greenland can be observed with relative safety. Because the collapse of the east Antarctic ice sheet will likely happen very rapidly, the sea level could rise by 52 meters in a very short period of time. We used to think the collapse was unlikely, or at least wouldn't happen for centuries. Now, it is looking like it could happen in our lifetimes.

"It's generally accepted that it's no longer a question of whether the West Antarctic Ice Sheet will melt, it's a question of when," said leader Ian Howat, associate professor of earth sciences at Ohio State in a 2016 study published in the journal Geophysical Research Letters. "This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes."

Boycott fossil fuels. Save the planet. Save our souls (SOS).

UPDATED October 30, 2022
A discovery made by researchers at Imperial College London, the University of Waterloo, Canada, Universiti Malaysia Terengganu, and Newcastle University, shows a river longer than the Thames beneath Antarctic ice sheet.

The study explains how the Antarctic ice sheet has a river running under it. The headline "longer than the Thames" isn't the thrust of the problem. Yes, it is adding a small amount to the rise in sea level. More importantly is not it's length but rather its width that is critical to our survival. A very wide and thin layer of water is separating the ice sheet from the surface... accelerating the expected time for the collapse of the Antarctic ice sheet. Global warming (the surface temperature measured in tenths of a degree over time) is fairly irrelevant when compared to the collapse of the ice sheet. Before we reach +2C, the Antarctic ice sheet will collapse. When the ice sheet collapses, life as we know it will change. In many ways it will be similar to a meteor hitting the ocean. Dr. William Colgan said, "A collapse of the colossal east Antarctic ice sheet, would lead to a 52-metre rise in sea levels..." Besides the instant wiping out of all coast lines, there would likely be tsunamis and other impacts including an acceleration in global warming as the surface is turned from reflective ice to heat absorbing dark surfaces.

The study finds:
An unexpected river under the Antarctic ice sheet affects the flow and melting of ice, potentially accelerating ice loss as the climate warms.

The 460km-long river is revealed in a new study, which details how it collects water at the base of the Antarctic ice sheet from an area the size of Germany and France combined. Its discovery shows the base of the ice sheet has more active water flow than previously thought, which could make it more susceptible to changes in climate.

The discovery was made by researchers at Imperial College London, the University of Waterloo, Canada, Universiti Malaysia Terengganu, and Newcastle University, with the details published today in Nature Geoscience.

Co-author Professor Martin Siegert, from the Grantham Institute at Imperial College London, said: “When we first discovered lakes beneath the Antarctic ice a couple of decades ago, we thought they were isolated from each other. Now we are starting to understand there are whole systems down there, interconnected by vast river networks, just as they might be if there weren't thousands of metres of ice on top of them.

"The region where this study is based holds enough ice to raise the sea level globally by 4.3m. How much of this ice melts, and how quickly, is linked to how slippery the base of the ice is. The newly discovered river system could strongly influence this process."

Water sources
Water can appear beneath ice sheets in two main ways: from surface meltwater running down through deep crevasses, or by melting at the base, caused by the natural heat of the Earth and friction as the ice moves over land.

However, the ice sheets around the north and south poles have different characteristics. In Greenland, the surface experiences strong melting over the summer months, where immense amounts of water channel down through deep crevasses called moulins.

In Antarctica, however, the surface doesn't melt in sufficient quantities to create moulins, as the summers are still too cold. It was thought this meant that there was relatively little water at the base of the Antarctic ice sheets.

The new discovery turns this idea on its head, showing there is sufficient water from basal melt alone to create huge river systems under kilometres-thick ice.

Improving predictions
The discovery was made through a combination of airborne radar surveys that allow researchers to look beneath the ice and modelling of the ice sheet hydrology. The team focussed on a largely inaccessible and understudied area that includes ice from both the East and West Antarctic Ice Sheets and reaches the Weddell Sea.

That such a large system could be undiscovered until now is testament to how much we still need to learn about the continent, says lead researcher Dr Christine Dow from the University of Waterloo.

She said: "From satellite measurements we know which regions of Antarctica are losing ice, and how much, but we don't necessarily know why. This discovery could be a missing link in our models. We could be hugely underestimating how quickly the system will melt by not accounting for the influence of these river systems."

"Only by knowing why ice is being lost can we make models and predictions of how the ice will react in the future under further global heating, and how much this could raise global sea levels."

For example, the newly discovered river emerges into the sea beneath a floating ice shelf -- where a glacier extending out from the land is buoyant enough to begin floating on the ocean water. The freshwater from the river however churns up warmer water towards the bottom of the ice shelf, melting it from below.

Co-author Dr Neil Ross, from the University of Newcastle, said: "Previous studies have looked at the interaction between the edges of ice sheets and ocean water to determine what melting looks like. However, the discovery of a river that reaches hundreds of kilometres inland driving some of these processes shows that we cannot understand the ice melt fully without considering the whole system: ice sheet, ocean, and freshwater."

A changing Antarctica
The existence of large under-ice rivers also needs to be taken into account when predicting the possible consequences of climate change in the region. For example, if summers warm enough to cause enough surface melt that the water reaches the base of the ice sheet, it could have large effects on the river systems, potentially tipping Antarctica to a Greenland-like state, where ice loss is much faster.

There are also potential feedback loops that would accelerate ice loss. For example, if the ice starts to flow faster as water accumulated at the base, then this will increase friction where the ice runs over dry land, which could increase the amount of basal melting and water produced.

The team are now looking to gather more data about all these mechanisms from surveys to apply their models to other regions and provide a better understanding of how a changing Antarctica could change the planet.

Antarctica's Collapse Could Begin Even Sooner Than Anticipated
The article in Scientific American states, "Two expeditions to the Thwaites Ice Shelf have revealed that it could splinter apart in less than a decade, hastening sea-level rise worldwide.

"As Scambos and Wild gazed down from their Twin Otter plane this past January, they spotted several new tears in the shelf -- three kilometers long and several hundred meters wide -- where it lifts off the seafloor. Ragged cliffs of ice tilted 50 meters up into the air, exposing deep layers that had not seen daylight for thousands of years. "I think it’s losing contact with everything that used to be bracing it," Scambos says. Not only is the ice shelf separating from its pinning point. As it speeds up, it is also stretching and tearing away from the glacier upstream.

The team was so alarmed that Pettit and Wild decided they will return this December to install a new instrument station: "BOB," short for Breakup Observer. They hope BOB will survive long enough to record the final throes of the ice shelf as it fractures into shards. It might not take long."

Greenland Rainfall and Albedo Feedback
The WMO (World Meteorological Organization) released the report State of the Climate in Europe 2021. "Temperatures in Europe have increased at more than twice the global average over the past 30 years -- the highest of any continent in the world. As the warming trend continues, exceptional heat, wildfires, floods and other climate change impacts will affect society, economies and ecosystems, according to a new report from the World Meteorological Organization (WMO)."

"Temperatures over Europe have warmed significantly over the 1991-2021 period, at an average rate of about +0.5℃ per decade. As a result, Alpine glaciers lost 30 meters in ice thickness from 1997 to 2021. The Greenland ice sheet is melting and contributing to accelerating sea level rise. In summer 2021, Greenland saw a melt event and the first-ever recorded rainfall at its highest point, Summit station."

Atmospheric rivers are narrow bands of moisture that travel across the lower troposphere and can carry as much water through the sky as the Amazon River. Atmospheric rivers have been putting serious rainfall melt on Greenland for the last decade. The study Atmospheric River Impacts on Greenland Ice Sheet SurfaceMass Balance found, "Furthermore, our investigation of the short- and long-term relationships between moisture transport vents and modeled GrIS surface properties proves that this correspondence between the years of enhanced AR activity and anomalous GrIS mass loss is not a coincidence. Strong atmospheric river impacts cause increased melt in all areas of the GrIS and decreased SMB in the ablation zone during summer, and warm seasons with above-average GrIS melt extent are characterized by anomalously strong moisture transport by atmospheric rivers over Greenland. ARs typically result in SMB gains in the GrIS ablation zone during nonsummer seasons and in the accumulation zone during all seasons. However, the intense summer SMB losses in the ablation zone during years of enhanced moisture transport outweigh the positive atmospheric river contributions to SMB in other regions and seasons. The scaling of melt versus snowfall in Figures 9 (right) and 11 shows that the magnitude of mass loss from summer melt in the ablation zone has a much greater upper limit than mass gain from snowfall."

Does the rainfall have a significant impact? Yes; however, it is the Albedo Feedback that is of the most concern.

"It turns out that the rain itself wasn't the most important factor," says Prof. Jason Box from GEUS and lead author of the paper Greenland Ice Sheet Rainfall, Heat and Albedo Feedback Impacts From the Mid-August 2021 Atmospheric River reporting their results in Geophysical Research Letters.

"There is an irony. It's not really the rain that did the damage to the snow and ice, it's the darkening effect of the meltwater and how the heat from the event erased snow that had overlaid darker ice across the lower third of the ice sheet."

"Unusually warm atmospheric rivers swept along Greenland in the late summer months, bringing potent melt conditions when the melt season was drawing to a close."

"The researchers found that, between 19 and 20 August 2021, this melt caused the altitude of the ice sheet's snowline near Kangerlussuaq to retreat in elevation by a whopping 788 metres, the snowline retreated, exposing a wide area of dark bare ice. Under normal circumstances, snow would cover and insulate this ice, but the snow melted suddenly and exposed the ice to heat, causing even more melting."

"The authors conclude that the heatwave causing the rain event serves as an excellent example of 'melt-albedo feedback that amplifies the melt impact of the initial melt perturbation'".

1/3 of World Heritage Glaciers Will Disappear by 2050
The United Nations says, "New UNESCO data highlight the accelerated melting of glaciers in World Heritage sites, with glaciers in a third of sites set to disappear by 2050. But it is still possible to save the other two thirds, if the rise in global temperatures does not exceed 1.5℃ compared to the pre-industrial period."

The UNESCO report World Heritage Glaciers found:

Glaciers across the globe -- including the last ones in Africa -- will be unavoidably lost by 2050 due to climate change.

Glaciers in a third of UN World Heritage sites will melt within three decades.

Mount Kilimanjaro's last glaciers will vanish as will glaciers in the Alps and Yosemite National Park in the US.

They will melt regardless of the world's actions to combat climate change.

50 UNESCO World Heritage sites are home to glaciers (A total of 18,600 glaciers have been identified in these 50 sites, covering around 66,000 km2), representing almost 10% of the Earth’s total glacierized area. They include the highest (next to Mt. Everest), the longest (in Alaska), and the last remaining glaciers in Africa, amongst others, giving a representative overview of the general situation of glaciers in the world.

But a new study by UNESCO, in partnership with IUCN, shows these glaciers have been retreating at an accelerated rate since 2000 due to CO2 emissions, which are warming temperatures. They are currently losing 58 billion tons of ice every year -- equivalent to the combined annual water use of France and Spain -- and are responsible for nearly 5% of observed global sea-level rise.

Only one effective solution: quickly reduce CO2 emissions
The report concludes that glaciers in a third of the 50 World Heritage sites are condemned to disappear by 2050, regardless of efforts to limit temperature increases. But it is still possible to save the glaciers in the remaining two thirds of sites if the rise in temperatures does not exceed 1.5℃ compared to the pre-industrial period.

"We hope we might be wrong, but this is the hard science," said UNESCO project officer Tales Carvalho Resende, one of the authors. "Glaciers are one of the valuable indicators of climate change, because they're visible. This is something we can really see happening."

The remaining glaciers in the other two thirds of UN World Heritage sites could be saved, but only if the world limits global warming to 1.5℃, the authors say. Another UN report last week found that the world currently had "no credible pathway" to achieve that.

"What is quite unprecedented in the historical record is how quickly this is happening," said Beata Csatho, a glaciologist from the University of Buffalo. "In the middle of the 1900s, glaciers were quite stable," she said. "Then there is this incredibly fast retreat."

"This is really a call to take action at every level -- not only at the political level, but at our level as human beings," said Carvalho Resende.

"Doomsday" Thwaites Glacier Could Suffer Periods of Rapid Collapse
In April of 2023, the study Rapid, buoyancy-driven ice-sheet retreat of hundreds of metres per day was pulished in the Journal Nature. "Our research provides a warning from the past about the speeds that ice sheets are physically capable of retreating at," said Dr Christ'ne Batchelor at Newcastle University in the UK, who led the research. "It shows that pulses of rapid retreat can be far quicker than anything we've seen so far." A rise expected over 200 years could actually occur in 20 years, Batchelor said.

The Guardian reported:

The research, published in the journal Nature, used high-resolution mapping of the sea bed off Norway, where large ice sheets collapsed into the sea at the end of the last ice age 20,000 years ago. The scientists focused on sets of small ridges parallel to the coast, which formed at the line where the base of the ice sheet met the oceans, called the grounding line.

As the tides lifted the ice sheets up and down, sediments at the grounding line were squashed into ridges twice a day. As the base of the ice sheet melted over days and weeks, the grounding line retreated towards the shore, leaving behind sets of parallel ridges. Measuring the distance between the ridges enabled the scientists to calculate the speed of the Norwegian ice sheet collapse.

They found speeds of between 50 metres a day and 600 metres a day. That is up to 20 times faster than the speediest retreat recorded previously by satellites, of 30 metres a day at the Pope Glacier in West Antarctica. Ridges had been studied before, in Antarctica, but only over an area of 10 sq km. The new study covered an area of 30,000 sq km, and 7,600 ridges, allowing the scientists to understand what is likely to control the rates of retreat.

On 21 April, 2023, the World Meteorological Organization released the annual report highlighting the continuous advance of climate change. Concentrations of the three main greenhouse gases -- carbon dioxide, methane, and nitrous oxide -- reached record observed highs in 2021. Real-time data from specific locations show levels of the three greenhouse gases continued to increase in 2022. Sea ice in Antarctica dropped to 1.92 million km2 on February 25, 2022, the lowest level on record. Ocean heat content reached a new observed record high in 2022. Global mean sea level (GMSL) continued to rise in 2022, reaching a new record high for the satellite altimeter record (1993-2022). The rate of global mean sea level rise has doubled between the first decade of the satellite record (1993-2002, 2.27 mm/yr) and the last (2013-2022, 4.62 mm/yr). Record breaking rain in July and August led to extensive flooding in Pakistan. Drought gripped East Africa. Record breaking heatwaves affected Europe during the summer.

"The world's glaciers melted at dramatic speed last year and saving them is effectively a lost cause as climate change indicators once again hit record highs. Antarctic sea ice fell to its lowest extent on record and the melting of some European glaciers was, literally, off the charts," the WMO said. "We have already lost the melting of the glaciers game, because we already have such a high concentration of CO2," WMO chief Petteri Taalas told reporters. In the Swiss Alps, "last summer we lost 6.2 percent of the glacier mass, which is the highest amount since records started."

"This is serious," he said, explaining that the disappearance of the glaciers would limit freshwater supplies for humans and for agriculture, and also harm transport links if rivers become less navigable.

Could this result in the fastest rise in sea levels ever?

Sidd Mukherjee replied:
Mmmm... how long is "ever?"

I don't think there is enough ice to do more than 200 odd feet or so all told.

I think we have lost Greenland and West Antarctica.

I think Greenland will melt in place, over a century or three, for a total of 20 odd feet.

West Antarctica could go very fast, maybe decades to a century. Say another 10 odd feet.

Between those two call it 20 feet of sea level rise over the next century.

If averaged, that works to 2 inches/year (or 50 mm a year.) Ten times the current rate. But, most of it will come in pulses toward the end

So we could dawdle along at half-an-inch a year, then have a couple years at a foot a year.

If we can keep CO2 equivalents to 500 ppm or so, we may be able to hold East Antarctica; however, if that goes, expect another couple hundred feet of sea level rise.

In The Reign of Violent Rain, Sidd said, "Now I am thinking the violent rain will be a bigger problem before we die... still thinking it through. In the long run, yes, sea level rise will hit big. If you look at the history, it is episodic, and in the fast bits it can go up 3 feet every twenty years for five hundred years. But, the rain intensity is increasing faster today, and drainage cannot cope, whether in the city or out, culverts and such put in over the last hundred years cannot handle. So, I am paying a lot of attention to terrain and drainage far inland from the seacoast (like Ohio.)

We expect sea level rise will total about 270 feet over the next several millenium. In 1998, the State of New Jersey published Sea Level Rise in New Jersey with a depiction of the Statue of Liberty with 270 feet in sea level rise.

In the last melting of the glacial maximum, the first 500 years saw a "pulse" of high rate sea level rise of about 500 years duration resulting in about a 66 foot rise in sea levels.

Updated November 21, 2023
On November 20, 2023, the UN's Emission Gap Report found even if countries carried out their current emissions-reduction pledges, the world would likely continuously exceed +3C degrees of warming this century. Later that day, the International Cryosphere Climate Initiative released State of the Cryosphere Report 2023 saying, "Two degrees is too high. Our message -- the message of the Cryosphere -- is that this insanity cannot and must not continue. The melting point of ice pays no attention to rhetoric, only to our actions."

Also see:
Measuring Sea Level Rise, Storm Surge, and Gravity

Antarctic Ice Sheet Is Melting at Accelerated Rate

Unavoidable future increase in West Antarctic ice-shelf melting over the twenty-first century