The secret life of glaciers
I’ve studied glaciers for most of my adult life, starting in geography classes as a teenager, when I was enthralled by the notion that at the peaks and poles of our planet there were giant rivers of moving ice that engulfed entire valleys and swept up all in their path.
Over my 25-year career as a glaciologist, their majesty has dwindled as our climate has warmed. I’ve witnessed this diminishing with my own eyes. The Haut Glacier d’Arolla in Switzerland, the very first glacier I visited as a 20-year-old undergraduate, has shrunk by more than one kilometre in length, thinned and lost one of its limbs since the 1990s. When I revisited it in 2018, I was stunned to see it slumped like a corpse in its eerie shroud of a valley.
Further sorth in the Andes of Peru, tropical glaciers I’ve studied have lost a staggering 30 per cent of their area in the past two decades. What’s more, their retreating ice has exposed garish swaths of metal-rich rocks, liberating toxic metals and acid to rivers and lakes. The lifelines proffered by glacier melt rivers in this arid region are becoming undrinkable.
Satellites orbiting our planet can now track the size of almost every glacier in the world — more than 200,000 of them. Writing in the journal Nature earlier this year, Romain Hugonnet and colleagues revealed that the thinning of glaciers (outside of ice sheets) had doubled in pace over the past two decades alone.
Several international groups show that loss of ice from our ice sheets is also accelerating, and in some cases worryingly tracking worst-case climate warming scenarios forecast by the Intergovernmental Panel on Climate Change.
But there’s more to this tale than the transfer of water from glacier to ocean. In fact, there is a magical and rather extraordinary dimension to glaciers that has been hidden from the public eye, but which is deeply wrapped up in their fate. This is that glaciers are alive.
Imagine you are sitting beside one of the raging rivers that tumble from a glacier’s front, and scoop some of its cloudy, frigid water into a bottle.
Its cloudiness is created by a swirling mass of fine particles, once part of the glacier’s bed but sanded down by the basal layers of the glacier before being swept up by flowing meltwater. These tiny particles are called “glacial flour”. Clinging to them you would find thousands of microbial cells — the only living inhabitants of a glacier (save for a passing polar bear or Arctic fox).
I first discovered the curious marvels of glacial flour when working in Greenland in 2012, at the formidable Leverett Glacier. Wind-swept, wild and remote, our camp there became known as “Camp Famine”, due to the food shortages we often encountered at the end of field seasons. Leverett’s river was a terrifying sight; a huge, writhing mass of grimy meltwater.
Back then, when I looked at the river, all I saw was dirty water. Yet as we started to take samples of this cloudy substance, we realised there was a lot more to it. First, we found that Greenland glacial flour (and its meltwater) was packed full of rock-sourced nutrients such as iron, phosphorus and silicon and came with its own population of microbes, which were living off the rock and liberating its nutrition. These microbes helped dissolve the rock by chemical reactions, and in doing so obtained energy and carbon to grow — a microbial cottage industry.
Researchers working around the edges of Greenland show the potent effects of the ice sheet’s meltwater and glacial flour. Deep fjords fringe much of the ice sheet and act as holding bays for its meltwater. Where glacier tongues reach the heads of the fjords, melt rivers pop out of glacier fronts well beneath the fjord surface, like a cold-water Jacuzzi. These stir up the water column, bringing nitrogen to the surface — nourishment for the phytoplankton, the base of local food webs. Beyond the fjords, fresh glacial meltwaters and flour are swept offshore by currents and seem to deliver a further nutrient boost to marine life.
If these glaciers shrink and retreat to land, the phytoplankton’s food source will reduce or be cut off. This could happen in many places in the world where you have ice flowing into a fjord or sea — Svalbard, the Canadian Arctic, Greenland, Alaska, Patagonia and so on. In Greenland alone, fisheries are the primary source of export income, and halibut like to skulk within the fjords. If the fjords become less productive, the halibut catches will fall. Marine economies could collapse.
In Antarctica, icebergs replace meltwater as the main type of freshwater couriered from the ice sheet to its oceans. Yet, we see something similar. Flotillas of icebergs drifting offshore are packed full of iron, released from Antarctica’s rock base by chemical reactions involving the microbes. The growth of phytoplankton in the Southern Ocean is limited by the scarce availability of iron. If you give them more, they grow more, feeding larger organisms such as Antarctic krill. We think that rusty icebergs might sustain a lot of the Southern Ocean’s phytoplankton growth, sucking up carbon dioxide from the atmosphere, and supporting valuable food-webs.
There is a sinister side, though, to glacier life. Often within glacial flour, you find carbon — the fundamental building block for life — because when our ice sheets formed, they entombed soils, vegetation and other dead things. One type of microbe that thrives at the bottom of an ice sheet is a methanogen (a “methane maker”); just like in rice paddies, landfill sites and the stomachs of cows, places where we are worried about production of this potent greenhouse gas.
In 2015, we turned up at Leverett Glacier armed with a special device to measure methane in the deep field — a sensor designed for the oceans and never used before in glaciers. What we found was incredible: the river waters were saturated with the gas, making the bottom of the ice sheet a giant methane-producing wetland. Since then, other researchers have found methane coming out of small glaciers, and even in lakes beneath the Antarctic ice sheet.
We are not sure how much methane lies beneath ice sheets, what form it is in and whether it could come out if the ice retreats. It’s certainly not something we have factored into future greenhouse gas emission targets to keep warming to within the 1.5C ambitions of the 2015 Paris Agreement.
It is too late to stop all future glacier retreat — our atmosphere is too loaded with greenhouse gases. Even if we meet the ambitions of the 1.5C Paris Agreement, Ben Marzeion and colleagues estimated last year that we would lose about a tenth of the Earth’s glaciers anyway by 2050, and more than half in sensitive spots like the tropics, because that change is locked in.
But our future path of greenhouse gas emissions could make all the difference, with the percentage loss of world glaciers by 2100 roughly doubling between low and high emission paths, with upwards of 80 per cent glacier losses for some regions under worst-case scenarios. This is a vast envelope of possibility for mountain regions which globally host more than 700m people, and who in the Himalayas, Andes and other developing regions have limited capacities to adapt to changed water supply.
For our ice sheets, aggressive action now could determine whether we cross what are called “tipping points”, when slow change gives way to fast and irreversible glacier loss and rapid sea level rise.
As for the effects of melting the homes of our glacier microbes — we are still learning. These tiny organisms seem to amplify some of the physical changes happening in glaciers. For example, pigmented glacier algae clinging to the Greenland ice sheet’s melting surface in summer darken the ice surface and have been shown by the Black and Bloom project to raise melting by more than 10 per cent.
Methane locked away in our ice sheets could be released as the ice thins and retreats, amplifying greenhouse gas concentrations and warming. Entire coastal ecosystems, including lucrative fisheries, may collapse if the glacial conveyor belts of nutrition switch off. But these are dimensions to glacier change that have been discovered too recently to narrow the envelope of uncertainties. The jury is still out for them.
I would never have imagined when I started out on the Haut Glacier d’Arolla 25 years ago, that I would come to witness devastating news reports weekly of glaciers thinning, retreating, even dying.
It’s true to say that glaciers have grown and shrunk in many past phases of Earth’s history as our climate naturally cooled and warmed, but what we are seeing now is unprecedented in human history — and it’s happening with nearly 8bn people on the planet, many of whom have come to rely on glaciers for fresh and clean water, fisheries, stable seas and a habitable climate.
We are at a defining moment in the history of our planet and face a sobering task in the run-up to COP26 in Glasgow this November, as world leaders set the level of their carbon-cutting climate ambitions, and we as individuals rethink how to live our daily lives to help. Recent records of global glacier change signal that we are sleepwalking towards a humanitarian crisis. The question is — will we choose to wake up?
Jemma Wadham’s ‘Ice Rivers’ is published by Allen Lane
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