Before the 19th century, the balance between incoming energy from the sun and outgoing radiation from the earth kept the planet's average temperature relatively stable. Only natural processes, such as volcanic eruptions and variations in solar output, caused periods of relative warming and cooling. Today, however, thanks to human-driven activities such as the burning of fossil fuels, industrial processes, deforestation and agriculture, global carbon dioxide levels are rising rapidly, which has led to an average global temperature increase of approximately 1°C since 1900.

This number may seem small, but the Arctic region has actually warmed by about 2°C in this time. This disparity in warming between the poles and the tropics is a phenomenon known as polar amplification. In just the last 30 years, areas of Arctic sea ice larger than Norway, Sweden, and Denmark combined have melted away. In the documentary Under Thin Ice, diver and underwater explorer Jill Heinerth travels to the Arctic regions of Greenland and Northern Canada to document what is happening above and below this rapidly disappearing ice. “The Arctic is changing faster than anywhere else on the planet,” says Heinerth. “And it's really evident here.”

There is a scientific explanation for why this is occurring. Fresh snow is the brightest natural surface on earth, as it reflects nearly 85% of solar radiation that hits it. Oceans, on the other hand, are the darkest natural surface on earth, and they only reflect about 10% of sunlight, absorbing the remaining 90%. In the winter, the Arctic Ocean is covered in ice, acting as an insulating blanket for the ocean below. In the springtime, this ice melts and exposes the dark ocean underneath, which leads to warming of the region, and this warming melts even more ice, resulting in a positive feedback loop. This process of polar amplification is stronger in the Arctic than it is in Antarctica, and this is because the Arctic is primarily an ocean covered in sea ice, while Antarctica is an elevated landmass that is covered in thicker layers of ice and snow. In fact, the average temperature of Antarctica has not changed in the last several decades, despite an increase in the concentration of greenhouse gases in the atmosphere. With more of the Arctic Ocean becoming free of ice in the summer, more waves are being generated. In summer, this surge in wave action breaks up large ice floes into smaller pieces, which melts the ice more quickly. In the autumn, large storms in the open ocean create more waves that cause the Arctic waters to mix with warmer waters, which increases the heat absorbed in the summer, making ice formation more difficult again in the autumn. These increased temperatures have also spread over the land. The Arctic land that was once covered in snow during the summer has shrunk in size significantly, and this darker land absorbs more heat than before, further warming the Arctic and the rest of the planet.

However, this melted water does not simply remain on the surface to freeze again in the fall. Instead, it sinks down into the ice sheet through large holes called moulins, which lubricates the ice sheet and causes glaciers to move more rapidly and release more icebergs into the ocean. The level of melting of the Greenland ice sheet is a major indicator of potential sea level rise; if it completely melts, global sea levels could rise by as much as 6 metres, endangering coastal cities and small island nations while making dangerous weather events, such as floods and hurricanes, even more deadly.

The most troubling effect of this feedback loop is the release of methane into the atmosphere. The Arctic stores an enormous amount of carbon, mostly in the soil, which is permanently stored in perennially frozen land called permafrost. Humans release around 9 billion tonnes of carbon dioxide per year through industrial activities. It is estimated that an astounding 14,000 billion tonnes of carbon exist in permafrost soil alone, or the equivalent of 155 years' worth of fossil fuel combustion. As this permafrost melts, plants and animals that were frozen under the ice begin to decay, and if there is no restriction on oxygen, this releases mostly carbon dioxide. However, if the soil is waterlogged, fermentation occurs and this discharges a gas called methane. Although it only lingers in the atmosphere for a fraction of the time, methane traps heat in the atmosphere around 23 times more efficiently than carbon dioxide.

As the situation nears its tipping point, a global campaign is underway to actually remove carbon dioxide from the atmosphere manually, using techniques such as Direct Air Capture, a process of capturing carbon dioxide directly from the air surrounding us, as opposed to direct capture from point sources, such as factories, and sequestering this carbon directly or utilizing it for other purposes. This is what plants do naturally, but Direct Air Capture does it much more rapidly and requires less land space. In addition, it delivers the carbon dioxide in a pure, condensed form that can easily be stored in the ground or reused. The success of such efforts will likely spell the difference between a prosperous and sustainable future for mankind and a descent into bleak, climate-driven chaos.