Part Two
ANTARCTICA – GLACIOLOGY
This lecture gave us an overview of how glaciers are formed, how they are affected by climate change, and how, in turn, these changes affect the entire planet.
He started off by telling us that planet Earth is currently in its Quaternary glaciation, one that began around 2.6 million years ago. During this period, enormous masses of ice covered much of the planet’s surface during glacial phases, alternating with warmer periods called interglacial phases, when the ice retreated. At present, we are living in an interglacial period that began roughly 11,700 years ago. Since ice sheets and glaciers are still present, the Quaternary period is still ongoing.
We then moved on to glaciers – moving masses of ice that can almost be thought of as living and breathing entities. Dense glacial ice forms through the accumulation and compaction of snow over many years, behaving in a way that’s surprisingly similar to metamorphic rock and leaving indelible landforms across the planet’s surface. When snow accumulates in bowl-shaped valleys known as cirques, its own weight causes it to compact into granular snow. Over time, more snowflakes accumulate and air bubbles become trapped, eventually forming glacial ice. When snow accumulation exceeds ablation, a glacier begins to form. While one might imagine glaciers as featureless blocks of ice, these wonders of nature are full of complex structures, including moraines – debris ridges left behind by moving ice; crevasses – deep cracks caused by stress and movement within the ice; and seracs – towering, unstable columns of glacial ice.
Contrary to how static they appear, glaciers are constantly on the move. Under their own immense weight, they flow downslope like slow, frozen rivers, creeping towards lower elevations and, in many cases, the sea. When the accumulation of snow and ice equals the melting and calving at the glacier’s snout, the glacier is said to be in equilibrium. When accumulation exceeds loss, the glacier advances; when loss exceeds accumulation, it retreats. Unfortunately, all but roughly 2% of glaciers worldwide are currently shrinking at an accelerating pace as temperatures rise and snowfall decreases.
While Earth’s climate has naturally fluctuated throughout its 4.6-billion-year history, carbon dioxide emissions and human activity have driven an unprecedented rate of warming over the past century, resulting in a significant reduction in global ice cover.
As temperatures rise, ice sheets begin to melt at the surface, with meltwater pooling and seeping down into crevasses. This weakens the internal structure of the ice and increases the rate of calving – the very process that produces icebergs. As glaciers thin, friction between the ice and the ground decreases, allowing them to accelerate, funneling even more ice into the ocean and compounding mass loss far beyond what surface melting alone would suggest.
Another key concept he introduced was the albedo effect. Ice and snow are highly reflective, bouncing a large proportion of incoming solar radiation back into space. As glaciers and ice sheets shrink, darker rock and open ocean are exposed beneath them, absorbing far more heat. This additional warmth accelerates further melting, creating a vicious feedback loop where ice loss directly fuels more ice loss. It’s one of the main reasons polar regions are warming faster than anywhere else on Earth.
Antarctica’s ice sheet, the world’s largest glacier system, contains around 90% of all the ice on the planet. Large parts of it, particularly in West Antarctica, rest on bedrock below sea level, forming what are known as marine ice sheets. These are inherently unstable. Once warmer ocean water intrudes beneath them and starts melting the ice from below, retreat can become self-sustaining and effectively irreversible on human timescales. This is why West Antarctica is considered especially vulnerable, even if global temperatures were to stabilise soon.
When large chunks of ice calve, they are carried by ocean currents into warmer waters where they eventually melt. This meltwater contributes to rising sea levels, but it also disrupts ocean circulation. Freshwater dilutes salty seawater, reducing its density and interfering with the sinking motions that drive global thermohaline circulation. Changes here don’t stay local – they ripple outward, altering weather patterns, weakening currents, and reshaping climate systems far beyond the polar regions.
Beyond ice loss alone, rising temperatures are also driving broader environmental changes, including shifts in geomorphic processes, air and water temperatures, precipitation patterns, atmospheric composition, and freshwater availability. Given that Earth’s rock and water cycles depend on finite systems, human activity has triggered an environmental shift rather than just climate change – a problem that has since become deeply entangled with politics.
Evidence from direct observation, instrumental records, and palaeoclimate reconstructions allows scientists to reconstruct environmental conditions stretching back through Earth’s history.
Ice cores drilled from glaciers and ice sheets contain trapped air bubbles whose gases can be extracted and analysed, revealing the composition of Earth’s atmosphere hundreds of thousands of years ago. Beyond serving as climate indicators, glaciers preserve layered records of past environmental conditions within their strata. For example, in Peru’s Quelccaya Ice Cap, the largest tropical ice cap in the world, perfectly preserved plant remains dating back around 5,700 years have been discovered. While glaciers are found across the globe, those in Greenland and Antarctica provide the longest continuous records, extending back roughly 200,000 and up to 800,000 to 950,000 years respectively.
Perhaps the simplest way to track changes in glacier size, and by extension the impacts of global warming, is by comparing photographs taken decades apart. The Larsen Ice Shelf on the Antarctic Peninsula looks drastically different today compared to its state before the major collapses that began in 2002. Similarly, the Brunt Ice Shelf calved in January 2023, producing a massive iceberg measuring around 1,550 square kilometres. And then there’s the Arctic sea ice pack, which has declined by roughly 12% per decade since satellite monitoring began in the late 1970s, with ice thickness decreasing by over a metre in some regions.
From these observations, scientists can also glimpse what lies ahead. The glaciers of Mount Kilimanjaro are expected to disappear within the next few decades. Hydroelectric plants that rely on glacial meltwater, such as those serving regions around Huaraz in Peru, may become obsolete as their water sources vanish. Perhaps the most unsettling aspect of all is the mismatch in timescales. Glaciers respond to change over centuries and millennia, yet humans have forced dramatic warming in just a few decades. We are pulling geological levers at a pace the Earth system was never designed to handle.
And with Keith being the cynic that he is, he didn’t end the lecture on a hopeful note. Instead, he told us we’re edging ever closer to being completely screwed – and that, ultimately, we are our own undoing.
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