The natural world and the balance of ecosystems that define life on our planet are manifest in many visible ways that fascinate us, shaping our lives while inspiring a sense of beauty, wonder, and curiosity—the instincts we transform into art, culture, and science. Yet, many of the processes and events that drive the natural world, despite their magnitude and importance, are invisible to our eyes. As scientists, environmentalists, members of society, consumers of culture, we are compelled to brave the challenge of uncovering the invisible forces that are a menace to the natural world, and, consequently, to us. These invisible forces have been unleashed by the silent and invisible emission of greenhouse gasses that have altered the equilibrium of our planet in a violent and sudden fashion through the prioritization of economic growth over protection of our natural resources and the attitudes of political leaders reminiscent of Pontius Pilate.

Consider Greenland, one of the epicentres of the global ice melt, the single largest active contributor to sea level rise (about 20–25% of the total). This ice melt and subsequent sea level rise occurs through the loss of ice mass during summertime, either through calving of icebergs or through the runoff of surface meltwater to the surrounding oceans. The two components contribute almost equally to the total mass loss and thereby to the sea level rise, posing all the attendant threats to the balance of the world. The ice loss would occur unobserved without a considerable investment by climate scientists.

Over the past few decades, the Greenland ice sheet has been losing mass at an accelerating rate. Along with soaring temperatures, the amount of solar energy absorbed by snow and ice is a major driver for promoting melting, becoming the major driver in the summertime. Brighter surfaces, like fresh snow, reflect up to 90% of the incoming solar radiation in the visible range of light, and that is why snow is so bright. On the other hand, dark, bare ice reflects only 30% of the radiation, hence absorbing more. The parameter that describes this property is called albedo (from the Latin albus, meaning whiteness): materials with high albedo reflect more light than those with a low albedo. It is worthy, here, to note that in the case of Greenland, the name itself evokes chromatic thoughts. According to legend, when the Viking explorer Erik the Red was banished from Iceland and reached the shores of Greenland, he realized he would need to call the barren land something special if he were to attract new settlers. He called the island “Grønland,” (Greenland) a name that would travel, telling tales of tender fruits and fertile land to unwitting sailors.

How does all this apply to the hidden light of Greenland? To better understand, we need to dive into the realm of spectral properties: the different surfaces on Earth all reflect solar energy in different ways, each with their own spectral fingerprint of sorts. Objects that we see as red, for example, reflect more red light, while those that look white, such as snow, reflect light in several wavelengths that combine to make the snow look white to our eyes. The property of a material to reflect light (and, therefore, energy) depends, on the wavelength of the light, which corresponds to a color in the visible spectrum. For reference, humans see in the visible spectrum with wavelengths ranging between 400 to 800 nanometers (one nanometer is one billionth of a meter), an incredibly small portion of the whole electromagnetic spectrum. An object’s spectral fingerprint changes during its lifetime, a little like changes in our hair color as we age. As mentioned, freshly fallen snow has a high albedo (very bright). As snow ages, which for snow is accelerated by the melting-refreezing cycles, its grains get larger through a process called constructive metamorphism wherein smaller grains bind through the film of liquid water that is created during the melting phase and then refreezes, acting as a glue. As this happens, the albedo in the near-infrared region (a region close to the red but invisible to our eyes) decreases, as the light has to go through more ice before bouncing back. However, the snow will still appear bright and white to our eyes because the changes do not considerably affect the visible region. In other words, the snow gets darker but we can’t see it! As an example, look at the images below. The one on the left looks familiar: a bright snowfield with dark trees and a medium bright sky. The one on the right shows the same scene as it would be perceived if we had near-infrared vision: here snow and sky are dark and trees are bright.

As snow gets older and goes through melting and refreezing cycles, which are occurring earlier and for longer because of increasing Arctic temperatures, it absorbs more and more energy which, in turn, promotes more melting, in a positive feedback mechanism that amplifies melting. I call this phenomenon “melting cannibalism.” Once bare ice is exposed, things go even faster. Ice is darker than snow, and this further accelerates melting. Again, these invisible phenomena are driving much of what’s happening even though nothing appears to have changed.

Melting cannibalism is further accelerated by the fact that in the Arctic summer the sun shines 24/7. In recent decades there has been a decrease in cloudy days, with the consequent increase of incoming solar radiation and the associated melting records of the past decade driven by exceptional atmospheric conditions, which many think are the Arctic’s response to global warming. Melting cannibalism iss another hidden mechanism that connects the transparent atmosphere to the invisible changes occurring on the ice sheet. Visualizing these connections and processes is not always trivial. The sounds below show one attempt to visualize these invisible processes through their “sonification,” the use of non-speech audio to convey information. In this case, daily albedo values are converted directly to one of 128 possible steel drum pitches and each note's velocity is inversely mapped so that low albedo yields low-pitched notes played with greater intensity. Sonifications can not only be used to convey visually information to visually imparied people, but they can map the information space in a multidimensional way that a graph on a paper cannot. Through the modulation of tones, tempo, intensity and the use of multiple instruments, it is possible to build a multidimensional landscape that carries the information and generates knowledge. In the example below, you will hear the albedo in the 1990s (when was high and melting was low), for example, to be relatively soft with minimal distortion. In the 2000s, when melting was high and albedo was low, you will distinguishably hear the louder and noisier sounds. You can discover the rest and find more sonifications on Greenland here: https://www.polarseeds.org/sounds.html.

The melting of Greenland and the associated sea level rise, combined with increased storm surges and extreme weather events could destroy society as we know it if we don’t heed the warnings. As a society, we are perpetrating violence on our planet by prioritizing economic growth over protection of our natural resources. We are responsible for invisible forces actively driving extinctions. Invisibility makes it easy to ignore the hidden, scientifically-proven realities. But we simply cannot. On the contrary, the more we learn about unseen processes, the more we realize they demand our attention, not just for science but also to promote our deeply human ethical and moral principles. After all, as important as we imagine ourselves, we too are invisible—invisible to our very planet, spinning as it is in the universe, with or without us.

[1] Note that these images have been created by the author to explain the process by altering the one available at https://en.wikipedia.org/wiki/Wikipedia:Featured_picture_candidates/Near_Infrared_Tree

[2] Note this is different from thermal infrared which uses the heat of the bodies to create the image