Drops of water rise from the sea and slowly gather in the sky to form clouds that drift across the land. As the air surrounding those clouds cools, tiny crystals form, and, in time, those crystals are released as snowflakes, falling down, down down, until they finally settle on mountain slopes and polar plateaus.

Viewed in isolation, each snowflake is but a blip. But compressed beneath the weight of time, they can transform into layers of ice, forming glaciers that cover the land. And, in this way, each snowflake becomes indistinguishable from the next until millions of snowflakes begin moving as one.

Inch by inch, this unified ice flows forward and backward, responding to the pull of the sea, the heat of the Earth, and changes in the air. As conditions change, the ice eventually gives way to water, and the water droplets flow downslope, through lakes and rivers, back towards the sea.

Then, the cycle begins again.

Over scales of Earth time, sheets of ice ebb and flow across the tapestry of our planet. They grind mountains into sediment, excavate valleys, sharpen ridges, and hollow basins. They dominate the land, and then disappear again, leaving traces still visible millennia later, if you look closely enough.

The more time I have spent working in icy landscapes like Antarctica, and studying the history and future of that ice, the more I have begun to see the world around me differently.

Flying over glacial valleys along the Antarctic coastline, the ice seems endless. White stretches across the horizon, interrupted only by isolated peaks and exposed cliff faces that hint at the mountains and valleys hidden beneath. Staring at those fragments of Earth peeking through the ice, I try to envision the landscape below, where stories of its long history lie hidden. Tales from tens of millions of years ago, when dense forests covered the land and warm temperatures persisted even through the polar night. Or remnants of its last warm period, fifteen million years ago, when its coasts were lined with beech trees and its interior was a tundra that closely resembled parts of New Zealand today.

When I come home to New Zealand, I realize I am surrounded by stories of its glacial past, but I am only just learning to recognize them. Sailing through the fjords of Fiordland, I am dwarfed by towering cliffs enclosing valleys carved by glaciers long past. Hiking through the Matukituki Valley, I see the sharp horns and arêtes from where past glaciers compressed the mountain ridges and the cirques on the mountain slopes carved by the head of a glacier long gone. It feels as if the mountains hidden beneath the Antarctic ice are being revealed to me, as the shape of the land and the subtle striations in the rock become reminders of the ice that once consumed this landscape.

As I move between these locations, my mind dances between the two. Antarctica becomes Fiordland’s past, Fiordland becomes Antarctica’s future.

The past, present, and future begin to blur until time no longer feels linear.

Now, whenever I find myself in a landscape shaped by ice, I try to look at it a bit deeper. I ask how it came to be, and look for the stories written into the land. And as I’ve dug into those stories, I’ve realized that to follow a glacier is not simply to follow ice. It is to follow the paths of water that the ice supplies, to understand the ecosystems and societies that have grown around them.

Look at a map of the world, and glaciers appear as the headwaters of civilizations. Trace the meltwater from a glacier, and you eventually find a river. Follow the river, and you find forests, floodplains, farms, fisheries, and cities with millions of people who may never see the glacier that provides the water they live on.

On the Tibetan Plateau, snow that falls onto glaciers eventually becomes the rivers that deliver water to more than a billion people, flowing through Pakistan, China, and Southeast Asia. In Lima, Peru, glacial meltwater from the Andes provides a bridge across arid months for millions of people in one of the world’s largest desert cities. Across Europe, meltwater from the Swiss Alps feeds rivers like the Rhône, sustaining vineyards, cities, and landscapes from the mountains to the Mediterranean.

And, here in New Zealand, glaciers feed braided rivers that irrigate farmland, generate much of our hydroelectric power, and sustain fisheries.

Until recently, I looked out at the landscape of today and just saw what it is, not what it was, or what it could become. I saw the glaciers, and the lakes and rivers that flow from them, but I had not yet learned to recognize the longer story connecting them.

Scientists use the term shifting baseline syndrome to describe the way each generation comes to accept the environment they inherit as normal. What once would have seemed extraordinary gradually becomes ordinary. Now, this happens not just generation to generation, but within our own lives.

Glaciers do not disappear all at once. They retreat metre by metre, season by season, year by year. Most changes on Earth unfold the same way, too gradually for us to notice from one day to the next. Instead, they quietly accumulate until, one day, we look back and realise the landscape has become something else entirely.

When I first moved to New Zealand, I never thought of its glaciers as part of the story of modern change. I saw the Southern Alps as the traces of an ancient ice age, their glaciers the last remnants of a distant frozen past.

But then, stories from those who remembered the glaciers not as they are today, but as they had been only decades before, changed that view.

One of the most iconic pictures of New Zealand is of Tasman Lake. Icebergs drift across its turquoise surface while the glacier terminates high at the far end of the valley, surrounded by steep walls of exposed moraine.

Fifty years ago, that lake did not exist and the Tasman Glacier still filled the valley.

Back then, mountain huts stood perched beside the ice, and you could drive for kilometres along an alpine road next to the glacier. Now, the glacier has retreated up valley by 7 kilometres. The road has crumbled away as the glacial moraines have collapsed, while the huts have been removed or relocated.

The landscape I had accepted as normal had been transformed within a single human lifetime. I had arrived in the middle of a story of rapid glacial retreat without noticing.

In the documentary Chasing Time, photographer James Balog compresses decades into minutes to make these invisible changes visible. By installing time-lapse cameras at glaciers around the world, ice that seemed motionless comes alive, flowing, fracturing, and retreating before our eyes.

Glaciers that had stood for thousands of years were vanishing in mere decades, with only the time-lapse cameras and personal memories as witnesses. Watching these clips, I get goosebumps, feeling the weight of it all in a way I rarely do… even though I spend my time as an Earth scientist immersed in the numbers behind these changes.

Because, even without the data or computer models, the story of change is surrounding us. It is written into the landscapes we walk through every day — we just need to learn to see it.

This was not the ending I had expected when I first started writing this piece, but the process of writing it led me here. To the simple power of noticing. Of pausing for a second, looking around, and really seeing the world we live in. Seeing the forces that shaped it in the past, appreciating the forces sustaining it today, and being mindful of the forces that will shape its future.

Share

Paid subscribers help keep these stories free for everyone, and I'm very grateful for all of you. If you'd like to support future work, you can also leave a tip below.

tip jar

Video postcard: The braided Matukituki River flowing through old glacial landscapes.

The ghost of a glacier

Walking the paths of glaciers past.

Through forests that inherited their soil, alongside rivers that inherited their valleys.

Traversing ridges sharpened by their passage, climbing above lakes that now fill the deep basins they carved.

The ghost of a glacier remains long after the ice has disappeared, its influence continuing to ripple through the world it left behind.

As the first raindrop falls, the water flows over the cooled remains of molten lava. The firestorms of early Earth have begun to cool, and water finally takes its liquid form, condensing from the steam and vapour that has filled the atmosphere.

This is no ordinary rainstorm. For millions of years, rain falls across landscapes of fresh rock, pooling in every basin and low-lying corner of the planet.

Slowly, as the water pools, the first oceans emerge.

Share

Over the millennia that follow, water continues its slow reworking of the planet. Ice advances across the land, then retreats once more to the sea. Rivers carve new paths across the landscape before fading from it once again.

Eventually, every inch of Earth will spend time underwater, one way or another.

As water moves across the land, it gathers minerals from the rocks it passes through. From mountain peaks and through river valleys, these minerals flow down to the sea. Slowly, these minerals accumulate and the ocean becomes salty.

The Earth shapes the seas just as the ocean shapes the land. In some places, sunlight and evaporation leave the water warmer and saltier. In others, rainfall, river water, or melting ice make it cooler and fresher. These differences change the density of seawater, causing vast masses of water to slowly shift and flow.

Together, they create a global network of currents that redistributes heat, nutrients, and life around the planet.

Imagine: a single drop of water enters the journey.

Over the course of roughly a thousand years, it travels across the world’s ocean, changing ever so slightly as it goes. Mixing with meltwater from a glacier. Absorbing heat from the tropics. Picking up nutrients from the deep sea. Carrying traces of every part of the planet it passes through.

Before that drop of water returns to its point of origin, it takes a final swift passage along the eastern coast of North America in the warm waters of the Gulf Stream.

My own story begins here, along the path of the Gulf Stream, where the salts of the sea first ingrained themselves in my blood.

Long before I understood ocean circulation, the power of the sea revealed itself with every hurricane that passed overhead. Turbulence built and dissipated in familiar cycles. As the winds howled around us, battering walls and roofs, the sounds of the storm cancelled out everything else.

What I did not understand then was that the water fueling those storms was itself part of a much larger story — one that stretched far beyond the coastline I grew up beside.

At the time, the world felt bounded by the places I knew. But the ocean was already telling a different tale. Water moved between continents. Heat travelled across entire ocean basins. Places that seemed impossibly distant were connected in ways I could not yet see.

Years later, I would learn to follow the water's journey north into the cold, wild North Atlantic. From there, I would trace its pathways across the globe, linking distant continents, polar ice sheets, tropical seas, and the deepest parts of the ocean. The further I followed it, the more connected the world became, and the more I began to understand the fragility of the balance that sustains those connections.

Subscribe now

For thousands of years, the balance between saltwater and freshwater has helped sustain the conveyor belt of currents that connect the ocean. These currents shaped the climates, seasons, and weather patterns around which human societies developed. Their influence easy to overlook when things are stable, and most visible when they begin to unravel.

Around 13,000 years ago, the Earth was warming as it emerged from the grip of the last ice age. Vast ice sheets that had covered much of North America were melting, releasing enormous amounts of freshwater into the North Atlantic. This tipped that delicate balance between salt and freshwater, with impacts felt across the planet.

Evidence preserved in ice cores, lake sediments, and ocean records suggests that parts of the Northern Hemisphere experienced a sudden return to colder conditions. This period, known as the Younger Dryas, interrupted a warming world for more than a thousand years.

The Younger Dryas left fingerprints not only in ice cores and ocean sediments, but in ecosystems and human societies. As climates shifted, landscapes and resources changed. Human populations adapted, migrated, and reorganised themselves in response to a rapidly changing world.

These records help us understand not only what happened, but what may happen next.

Today, vast quantities of freshwater are once again entering the sea as glaciers and ice sheets melt. As in the Younger Dryas, the balance between salt and freshwater is shifting. The difference today is that over eight billion people now live within — and depend on — the climate system these currents help regulate.

In the North Atlantic, meltwater from Greenland and increasing rainfall are diluting the salty waters that help drive one of Earth's great ocean circulation systems. Scientists are watching closely as the network of currents that includes the Gulf Stream shows signs of weakening.

Far to the south, Antarctica is releasing freshwater into the ocean at an accelerating rate. There, some of the densest waters on Earth are forming more slowly than they once did, potentially altering circulation patterns that extend far beyond the polar seas.

Together, these currents connect the tropics to the poles, the surface ocean to the abyss, and the past to the future. They play a central role in redistributing heat, oxygen, nutrients, and carbon around the globe, helping to shape the climates, ecosystems, and seasons that our modern human societies depend on.

No one knows exactly what the future holds. But the records preserved in ice and sediment show us how shifts in the movement of freshwater can alter the trajectory of the planet in dramatic and life-altering ways.

Right now, somewhere in the North Atlantic, a drop of water begins its descent into the deep ocean, starting another thousand-year journey. It carries with it traces of glaciers, rivers, storms, and oceans long past. But the balance that shapes that journey is shifting, and we are only just beginning to see what that means.

Tip Jar

Video postcard from the week: Waves roll in and out at Victory Beach on the Otago Peninsula

“The river is within us, the sea is all about us;
The sea is the land's edge also, the granite
Into which it reaches, the beaches where it tosses
Its hints of earlier and other creation”

T.S. Eliot, The Dry Salvages

We have not yet invented time machines, but we can already travel in time.

We cannot ourselves travel to the past and see the first human societies form, the first words written by a human hand, or the first life form emerge. But we can see the world that shaped these events. We can see the environments they occurred in - the oceans and forests that they moved through, and the air that they breathed.

We cannot ourselves travel to the future and see what we become, or how long we last on this magical rock with a paper-thin atmosphere. But we can see what the world might look like. We can see where water may flow and where it may not. Where food could grow and where it could not. Where we might survive and where we might not.

As a child, I used to dream of an invention that would allow us to see the formation of the Earth as we know it today. To be able to watch as the Colorado River worked across millennia to carve out the chasms of the Grand Canyon. Or as two parts of the Earth’s crust collided, pushing up the Himalayan Mountain range from the depths of an ancient ocean, leaving behind marine fossils now found on the peaks of Mt Everest.

Trying to understand the world around me was an escape from the world within me. Understanding what the world endured as it formed, and how it adapted to change, helped to shape my own resilience. This fascination with why the world is what it is now, and what it might become, evolved alongside my understanding of myself — how I got here and what I could become.

Because, really, where does the mind end, and the rest of the world begin?

Subscribe now

These childhood imaginations ultimately shaped my career and the research that I do, taking me to the deep depths of our ocean and the frozen corners of our world to understand the inner workings of these remote, mysterious ecosystems.

I learned how animals in the deep sea can create light through chemical reactions in their bodies, using that light both to communicate and to ward off predators in the darkness.

I came to understand how life has evolved to survive in frozen seas, like the adaptations in Antarctic seals that allow them to hold their breath for over 90 minutes as they navigate a world below thick sea ice with limited exit points.

I observed the limits of species and ecosystems when pushed to extremes, like how high temperatures can cause mass coral bleaching and mortality, and what it means when a reef disappears.

I did not set out to study the consequences of a changing climate, but when every system around you is changing, it inevitably becomes part of the story. To make sense of this change, I find myself returning to the same childhood instinct that first drew me to science: going to the past to understand what comes next.

Not because the past provides certainty, but because it provides context. Looking to the past helps to make sense of the changes we are witnessing now, and the futures they might create.

It may seem like things are spinning out of control out there, but uncertainty is not the same thing as unpredictability. Many of the trajectories we mapped out still hold true — the world is simply moving along them faster than we thought it would.

And there is a power in that. In knowing that uncertainty does not mean we are lost.

From the disappearance of sea ice in places where I once expected to find it, to shifts in the movement of the ocean I grew up alongside, we can chart future trajectories and identify where our actions still matter.

Through a series of upcoming essays, I'll explore some of these stories, searching for the clues the past still holds about the future we are creating.

Tip Jar

Postcard from the field:

Last week, we were out in Fiordland, Aotearoa New Zealand, beginning a study to explore the changing flux of greenhouse gases through fjord waters.

All around us, the scars of a glacial past remained visible in the landscape, now covered by rich green forests and endless waterfalls. Standing there, it was impossible not to think about how quickly a landscape can change, and how much of its history remains written into the world around us.