Glaciers, Cosmic Rays, and the Science of Ice

It was the third day at sea when the captain announced over the internal speaker system that we were finally approaching the Pio XI Glacier. The Pacific Ocean had been calmer since the night storm. Walking out onto the deck, I couldn't help but think that the sky was the same colour described by William Gibson in his most famous novel: the colour of a television screen, tuned to a dead channel.

As the ship got closer, Pio XI — the name of a famous Catholic Pope and the largest glacier in the Southern Hemisphere outside Antarctica — revealed itself in its electric-blue magnitude. What makes this glacier particularly interesting is not its size or colour, though, but its behaviour: unlike most glaciers around the world, Pio XI is advancing! While others are retreating, Pio XI has expanded by nearly 60 square kilometers since the mid-20th century.

Why is Pio XI growing?

The reasons for this anomaly are not entirely understood (which is cool, because it stimulates our curiosity), but scientists have proposed several factors:

• Local precipitation patterns: The Patagonian Ice Fields receive some of the heaviest snowfall on the planet. Increased precipitation could be feeding the glacier faster than it melts.
• Topography and fjord dynamics: The shape of the underlying rock could be preventing warm ocean currents from undermining the glacier, allowing it to grow rather than retreat.
• Volcanic activity: Patagonia sits on the Pacific Ring of Fire, and geothermal heating beneath the ice might be affecting the glacier in unexpected ways.

Unlocking glacial patterns with Nuclear Science and Cosmic Rays

This is where things get really interesting (at least for me) and why I am writing about Patagonia and glaciers in this newsletter: nuclear technologies and cosmic rays offer a way to study glacial history! In fact, one of the coolest (pun intended) tools in this field is cosmogenic nuclide dating. Read it again: cosmogenic nuclide dating. A method which allows us to determine how long rocks have been exposed to the atmosphere after being covered by ice for thousands (and thousands, and thousands) of years.

When glaciers retreat, they expose bedrock that has been shielded from cosmic rays for millennia. Once exposed, these rocks begin accumulating isotopes like Beryllium-10 (10Be), Aluminum-26 (26Al), Chlorine-36 (36Cl) produced by high-energy cosmic rays striking the surface. One can even see the effects of supernova explosions! By measuring the concentrations of these isotopes, scientists can reconstruct glacial movements over thousands, even millions, of years. This technique provides a much deeper understanding of glacier dynamics than simply looking at temperature records from the past century.

Did you know that the most recent glacial period occurred between about 120,000 and 11,500 years ago? Since then, Earth has been in an interglacial period called the Holocene.

Whisky, Ice, and the Truckers of Patagonia

As I was lost in wonder looking at all that ice, the captain prepared a more practical demonstration of glacial history. A zodiac team was dispatched to the glacier front, where they chipped off a bucket of Pleistocene ice to bring back on board. That night, as we sipped whisky served on the rocks — rocks being ancient glacial ice trapping tiny air bubbles from prehistoric atmospheres — I sat down with the other passengers and the crew, exchanging stories on our travels across Patagonia.

Most of the passengers were Chilean truck drivers, ferrying their cargo trucks from north to south. The Andes had cut Chile in half, forcing them to take the sea route instead of driving across roads that were not built yet. Among them were a few occasional backpackers like me, following in the footsteps of Bruce Chatwin, dreaming to reach Ushuaia, the world at the end of the world.

The Pío XI Glacier, also known as Brüggen Glacier, is estimated to be at least 10,000–30,000 years old, dating back to the last Ice Age (the Pleistocene epoch)

From Pio XI to Perito Moreno: a glacial contrast

A month later, I stood in front of another giant — the Perito Moreno Glacier on the Argentine side of the Andes. Unlike most of Patagonia’s glaciers, Perito Moreno has been considered stable for much of modern history, neither retreating nor advancing significantly. However, recent studies indicate that the glacier’s northern front has started to retreat, raising.

Standing there, in front of these glaciers, I loved to know that nuclear physics and cosmic rays are playing a role in trying to find an answer on the behaviour of glaciers. And on the contrast between the Perito Moreno’s stability and Pio XI’s expansion.

Beyond nuclear science: radio glaciology and other tools

While cosmogenic nuclide dating is a nuclear-based technique, other non-nuclear physics methods are also used to study glaciers. Radio glaciology, for example, involves sending radio waves through ice sheets to map their internal structure. Ground-penetrating radar can reveal hidden layers within the ice, helping us estimate past accumulation rates and ice flow dynamics.

Combined with satellite measurements, gravitational surveys, and seismic studies, these tools help reconstruct the story of glaciers beyond our own lifetime — offering a view of climate shifts over thousands, or even millions, of years.

Nuclear science, cosmic rays and physics

The modern conversation around glaciers often focuses on melting ice, but science requires a broader perspective than short-term headlines. Glaciers have been advancing and retreating long before the industrial era. Understanding their behaviour means looking at the full spectrum of natural influences — cosmic rays, geological changes, ocean currents, and volcanic activity — not just human impact.

This is where nuclear science, cosmic rays, and physics play a crucial role. These tools allow us to go beyond what we see in a single human lifetime and uncover the long-term patterns that shape our planet.

Read more

• Read more about Cosmogenic nuclide dating
• The Table on the cosmogenic isotopes systematics was taken from this reference: Cosmogenics | GreenDrill
• An article rich of details and information about the Pio XI glacier: Glaciar Pio XI – Glaciología
• Want to see the Pio XI glacier in Patagonia with your own eyes? They have definitively improved access compared to 20 years ago, when I have been there. You can find some information on the new Navimag routes here: Explora la Patagonia en Ferry | Navimag

About me

I’m passionate about radiation and radiation safety, and I lead these efforts at a top MedTech company. My experience includes working with the European Commission and international physics laboratories, where I developed my expertise in nuclear physics (without causing any explosions!). With a PhD in applied nuclear physics, I’ve published research in peer-reviewed journals and enjoy crafting content that makes complex topics in science, safety, and security accessible and engaging—because everyone loves a good science story!

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