The world is evolving into disaster at an ever increasing pace. One global conference after the other is failing both humankind and all other creatures on this planet. We know that, at one point, the glaciers on Antarctica will destabilise and ultimately melt as a consequence of human created climate change, but this eventuality is considered very far off into the future. The melt will take many hundreds of years – possibly even more than half a millennium. At least, his is what we thought. Recent literature proves that we were wrong.
The culprit is marine ice-cliff instability (MICI). An understanding of what happens to glaciers under conditions of rising temperatures had been rather rudimentary, until Bassis developed a new theoretical model in his PhD (2002). In the old understanding, in a stable glacier-ice shelf system, the glacier’s downhill movement is offset by the buoyant force of the water on the front of the shelf. When warmer temperatures destabilize the system by lubricating the glacier’s base and creating melt ponds that eventually carve through the shelf, the ice shelf retreats to the grounding line, the buoyant force that used to offset glacier flow becomes negligible and the glacier picks up speed on its way to the sea. But MICI adds another instability process to this. Bassis proved that MICI can lead to the rapid collapse of glaciers. Research established that this is exactly what is happening in Greenland and in Antarctica. How rapid exactly the process evolves is unclear. According to the experts, Antarctic glaciers could become destabilised in twenty to fifty years from now.
The basic insight behind MICI is that, when glaciers are being eaten away simultaneously from above (warmer air) and below (warmer waters) and start to crumble, they increasingly expose taller cliffs which eventually become so tall that they are unable to support their own weight, so they crumble more, exposing taller cliffs, so bigger pieces break off. The destruction of the mouth of the glacier destroys the plug to the ice inland, making it easier for it to move towards the shore. In other words, warmer temperatures destabilise the glaciers so that they start collapsing because of their own weight. Once this process gets going, the ultimate destruction is baked into the glacier’s very structure.
Figure 1: Instability processes: The diagrams depict marine ice sheet instability (left) and marine ice cliff instability (right). (a) shows a stable system where the ice shelf buttresses the ice sheet behind it, but warm ocean water melts the ice. Melt shortens the ice shelf (b), and reaches all the way to the grounding line (c). (d) shows ice shelf crevassing and calving. Calving continues (e), and retreats until the ice cliff rises far enough above the water surface to become unstable (f). Image from DeConto and Pollard 2016 (see here).
In an article for Grist, Eric Holthaus reports on the fate of two glaciers in Western Antarctica (see here). Each of the glaciers, Pine Island and Thwaites, stretch inland for more than 150 miles. Both have been advancing for millennia toward the Amundsen Sea. Inland, the glaciers widen into a two-mile-thick reserve of ice covering an area the size of France. As Holthaus writes, they are two of the largest and fastest-melting glaciers on Antarctica. Together, they act as a plug holding back enough ice to increase sea-level with 3.35 meters (11 feet) – enough to submerge every coastal city on the planet (see here).
Figure 2: Map of Antarctica, showing the location of glaciers and ice movement (see here).
Antarctica spans an area about half the size of Africa, it is 14 millions square km. To compare, the area of the USA is 9.834.00 square km. The ice that covers it averages more than a mile thick (1.600 meters). Until a couple of months ago, it was sheer lunacy to suggest that all of this ice, or most of it, could destabilise in less than a century. Now, this is, at least, considered a more or less realistic possibility. “All over the world,” Holthaus writes, “high tides would creep higher, slowly burying every shoreline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees (…) All this could play out in a mere 20 to 50 years — much too quickly for humanity to adapt” (see here).
Instead of a three-foot (0.91 meter) increase in ocean levels by the end of the century as predicted by the IPCC, it is more likely that we will see a six feet (1.82 meter) rise. At least, this is what climatologists DeConto (from Massachusetts-Amherst) and Pollard (from Penn State), who incorporated the latest understanding of marine ice-cliff instability into a continent-scale model of Antarctica, predict. They warn that if carbon emissions continue to rise, the full 11 feet (3.35 meters) of ice locked in West Antarctica might be freed up (see also here).
As Holthaus writes, three feet of sea-level rise would be very bad, but this no longer seems to be realistically possible to avert. At six feet, Holthaus writes, around 12 million people in the United States would be displaced and several megacities would be wiped off the map (see here). There are, at the present, no plans anywhere. At 11 feet, however, land inhabited by hundreds of millions of people worldwide would disappear, cities would run under water, food prices would spike, millions of displaced people would be on the move, political institutions would break down.
Previous models suggested that it would take hundreds or thousands of years for sea-level rise of that magnitude to occur. But the new evidence says that once a certain temperature threshold is reached, ice shelves of glaciers that extend into the sea will melt from both above and below, paving the way for ice-cliff instability to do its ultimate job of demolition. As Holthaus adds, around 3 million years ago, when global temperatures were about as warm as they expected to be later this century, oceans were dozens of feet higher than today (see here). For now, floating ice shelves protect the two glaciers. They still function as a plug to the flow of ice into the sea. But the Larsen B ice shelf, for example, proves that once the ice shelves break, the glaciers start to flow faster toward the sea, thereby weakening the stability of ice further inland. Eventually, the whole glacier collapses (see picture below). The same process is at work in Greenland. The melting of the Greenland Ice Sheet would contribute as much as 20 feet (6 meters) of sea-level rise.
Picture 2: The collapse of the Larsen B glacier in 2002 (see here).
The question is, how fast will it go? An English-Swedish study (from the University of Cambridge, the British Antarctic Survey and Stockholm University) tried to answer the question by investigating thousands of marks on the Antarctic seafloor, caused by icebergs which broke free from glaciers more than ten thousand years ago (see here). These marks show how part of the Antarctic Ice Sheet retreated ‘rapidly’ (again) at the end of the last ice age, as it balanced precariously on sloping ground and became unstable. Today, as global climate continues to warm, rapid and sustained retreat may be close to happening all over and could trigger runaway ice retreat into the interior of the continent, which in turn would cause sea levels to rise much faster than currently projected.
Today, as warming waters caused by climate change flow underneath the floating ice shelves in Pine Island Bay, the Antarctic Ice Sheet is once again at risk of losing mass from rapidly retreating glaciers (see here). Significantly, if ice retreat is triggered, there are no relatively shallow points in the ice sheet bed along the course of Pine Island and Thwaites glaciers to prevent possible runaway ice retreat into the interior of West Antarctica. “Ice-cliff collapse has been debated as a theoretical process that might cause West Antarctic Ice Sheet retreat to accelerate in the future,” said co-author Robert Larter, from the British Antarctic Survey. “Our observations confirm that this process is real and that it occurred about 12,000 years ago, resulting in rapid retreat of the ice sheet into Pine Island Bay”(see here). The marks on the ocean floor do not tell the researchers how fast exactly the process evolved. However, the message is that it went quick – it did not take millennia or several centuries. It all happened in a relatively very short period of time.
That, then, is the bottom line: the melt will go fast and we are not preparing. Incredibly, we continue to race towards disaster. Globally, our emissions are rising. Temperature is rising (see here – thousands on articles, hundreds of thousands of pages of text, blogs, attacks, ‘scepticism’ and denying notwithstanding, there has never been a recent ‘pause’ in global warming). Radically insane as it is, the world continues to slash out enormous subsidies for fossil fuel companies. All the COPs and other conferences, ingenious talk about carbon markets, divestment, resilience and nice intentions take nothing away from the essential fact that the G20 countries subsidise fossil fuels by over $ 1.000 per citizen – a figure from the IMF (see here). Globally, fossil fuels are subsidised by $ 10 million every minute. In 2015, the subsidies to the fossil fuel companies were bigger than the health spending of all governments combined (see here), the total amounts to $ 5.3 trillion a year.
Figure 3: Greenhouse gases (GHGs) continue to rise (Source: NOAA).
The basic question is whether the world as a whole is worth more or less than the profits the companies make for their shareholders. It is a fantastically stupid question. So far the answer has been the wrong one. James Hansen, who was not allowed to address the COP23 meeting in Bonn, wants to prosecute all of the companies that are historically responsible for the CO2 problem. It is well-known that, historically, 67 multinationals are responsible for almost two thirds of all CO2 emissions. So, let’s prosecute them, say the litigation proponents. The polluters have to pay for the damage they caused. I wish Hansen good luck. At the same, it is just ridiculously naïve to think that this will solve the problem. Without fast and structural changes in the political economy of the world system, some of humanity (or all of it) has little future left.