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What Do We Mean by the Cryosphere?
Just to recap, the Cryosphere refers to all frozen water on Earth — snow, sea ice, lake and river ice, glaciers, ice caps, ice sheets, permafrost, and ice shelves. It forms a major component of the Earth system, strongly influencing climate, oceans, ecosystems and the global energy balance. Although frozen water appears across the globe, the Polar Regions contain its largest and most climate-critical components. I have had to split the Polar section into two parts as well, so watch out for Part II shortly.
If you thought things were looking bad in the Alps, the rate of warming in Polar Regions is even faster — closer to three to four times faster than the global average. As one researcher remarked in a journal article, the words "glacially slow" have taken on a new meaning.
If we hear little about these changes, it's most likely because because polar regions are vast, remote and seemingly indestructible. There are fewer people to witness and report events, and low population density means that localised impacts—such as coastal erosion affecting Inuit communities—rarely attract global attention in the same way that the near-total destruction of Blatten, a village in Switzerland, did. More broadly, public attention tends to focus on issues closer to home — interest rates, fuel prices, or the price of cabbage in the local supermarket. However they affect us in more ways than we might think.
Collapsing Glaciers and Melting Ice Sheets
Here is a glimpse of what is happening at the Poles. Because of rising temperatures and warming oceans, glaciers are melting from both the top and from underneath, leading to rapid ice loss.
Greenland — home to the world's second largest ice mass after Antarctica — lost 55 billion tons of water in just five days during 2019 alone -enough to cover Florida in five inches of water. Much the same is happening in Patagonia and Alaska.
In Antarctica, the Thwaites Glacier known as the "Doomsday Glacier" — is of particular concern to researchers because it is one of the world's largest and is also being rapidly undermined by warming seawater. Where glaciers meet the sea, their great ice walls hold back vast quantities of ice. When these collapse, huge quantities of water are released, adding to global sea level rise.
Sea Level Rise
Sea level rise is driven by two forces — meltwater from glaciers and ice caps, and thermal expansion — warm water expands and simply takes up more space than cold water. If all the world's glaciers and ice caps were to melt — which is unfortunately happening much faster than scientists predicted — water levels would rise by 67 metres, with dire consequences for many of the world's coastal cities. Satellite images already show Thwaites developing cracks extending into East Antarctica, causing scientists to worry that it could be gone in as little as three to five years.
As yet, sea level rise is making only a small — and somewhat uneven — difference around the world, due to the way winds, tides, global currents and the rotation of the Earth move water from one side of an oceanic basin to another. Another reason for variable readings is that as the immense weight of ice lifts off frozen landmasses, the land itself rises in what is called isostatic adjustment — a kind of rebound effect. [Isostatic adjustment also contributes to increasing tectonic activity around the world.]
For now, the main risks come from storm surges, because warmer waters generate more frequent and more intense rainfall and storms. The adaptations for sea level rise — seawalls, buffering with mangroves, salt marshes and wetlands, raising buildings, creating new islands at higher elevations, or complete relocation — have been discussed in earlier sections. This video provides a good recap.
Thawing Permafrost
Permafrost is soil, rock or sediment held together by ice. We have already discussed the effects of melting permafrost on the European Alps — how it accelerates the destabilisation of mountain slopes — in the previous post, but in Polar Regions it is far more extensive, reaching up to 1,500 metres deep in places such as Siberia. While there is little permafrost in the Southern Hemisphere, in snow-free parts of the Northern Hemisphere it can cover 15–25% of the landmass, reaching as far as 60°N.
Usually only the top one to two metres soften in spring and summer, but as the Arctic warms, thaw is becoming far more severe — creating sinkholes and causing buildings, roads, and pipelines across Alaska, Canada, Norway and Siberia to collapse.
Communities Under Threat
Coastal villages such as Shishmaref and Newtok in Alaska, and Tuktoyaktuk in Canada, are being forced to relocate as thawed ground collapses beneath them. Alaska alone has over 140 villages which are similarly affected.
Other Effects of Thawing Permafrost
Thawing permafrost releases large quantities of Methane, naturally occurring heavy metals, and ancient pathogens. Some Alaskan rivers are turning orange as permafrost thaws, threatening fish and local communities. The 2016 Siberian anthrax outbreak was linked to the exposure of thawed reindeer carcasses. Since then, several other instances have been recorded, particularly in migratory birds and as recently as the summer of 2025 and 2026.
While not yet a major issue in Antarctica, permafrost thaw there is destabilising ice-free coastal slopes, altering meltwater systems, and changing soil ecosystems that support microbial and moss communities. And those are just the visible effects. There is another, more insidious one.
How Melting Permafrost Drives Further Warming
Thawing Arctic permafrost is now recognised as a major driver of global climate instability. As frozen ground releases vast amounts of carbon dioxide and methane, it accelerates planetary warming and disrupts atmospheric circulation patterns such as the Jet Stream.
The Jet Stream arises from the strong temperature contrast between the poles and the mid-latitudes. As the Arctic warms faster — a phenomenon known as Arctic Amplification — that contrast weakens, causing the Jet Stream to meander more and leading to persistent weather extremes: prolonged heatwaves, stalled storm systems, severe cold spells, and unusual rainfall patterns across Europe, North America, and Asia. At the same time, the loss of reflective snow and ice exposes darker land surfaces that absorb more heat, amplifying Arctic warming still further — making permafrost thaw not only a geological hazard, but a key contributor to increasingly erratic global weather.
Shrinking Sea Ice
The Antarctic is a frozen continent covered and surrounded by ice, whereas the Arctic is a frozen sea that used to be covered by ice, but is increasingly less so. The rate of ice loss in the Arctic is no longer tied to emissions alone. It has taken on a life of its own, becoming a self-perpetuating cycle - higher temperatures mean less ice, dark waters absorb more heat, which causes more melting, which causes more heating, and so on. Dave Borlace* with his excellent Just Have a Think series explains it much better than I do.
This is also happening in Antarctica. In this video also by Dave Borlace, you can see the impact on ocean currents which we talked about in a previous post on the Marine Environment. There are no easy fixes other than rapidly reducing emissions, and even then, tipping points — or cascades, as researchers now call them because they rarely occur without knock -on effects — may already have passed the point of no return.
* Dave Borlace has a way of making physics comprehensible and does it in that very British understated way, so you might see quite a bit of him in this section.
Impact on Ocean Circulation
Melting polar ice is also reshaping global ocean circulation. As vast amounts of freshwater enter the seas, they dilute salt levels and disrupt the density-driven currents that normally transport heat around the planet. These shifts can slow major systems like the Atlantic Meridional Overturning Circulation (AMOC), altering weather patterns, sea temperatures, and nutrient flows. While the mechanics were explored in the marine section, it is worth emphasising that these changes ripple outward, influencing ecosystems far beyond the poles.
Why Is Warming Accelerating?
Ice caps and glaciers are the world's air conditioners — the ice in our global Esky. As they shrink, warming accelerates in two ways. First there is simply less ice to do the cooling, but then the newly ice-free areas absorb heat instead of reflecting it. This is the albedo effect, and it creates a powerful feedback loop.
Black Carbon — produced by burning vegetation, fossil fuels, or industrial activity — has a similar effect. Its darker surface draws heat to itself, accelerating melt wherever it settles on snow and ice.
Impact on Global Climate and Weather Systems
Changes to Winds and "Atmospheric Rivers"
One of the things that large frozen expanses do is pull warm air towards them, creating powerful atmospheric circulation belts. In the North, this produces the Jet Stream; in the South, the Southern Annular Mode (SAM), which brings the Westerlies to places like Tasmania.
In Arctic regions, warming is causing the Jet Stream to weaken and wobble, bringing erratic weather patterns — cold snaps and heatwaves — to Europe and North America. In the Antarctic, the SAM is shifting further south, meaning rain-bearing westerlies miss southern landmasses, causing droughts in South Africa, southern Australia, and South America, while intensifying rainfall at mid-latitudes.
ENSO — El Niño and La Niña
The El Niño–Southern Oscillation (ENSO) is a separate tropical Pacific oscillation that modulates the intensity of both systems. It is the main climate pattern driving alternating floods and droughts in southern Australia — essential for filling its reservoirs — and is equally important in Chile and Peru.
ENSO is becoming less reliable as polar warming alters the temperature gradients that drive atmospheric circulation. This disrupts the Walker Circulation across the Pacific, leading to more frequent, intense, and unpredictable ENSO events. ENSO also interacts with the SAM — amplifying or dampening its rainfall and temperature effects — making southern Australia's climate more variable and increasingly difficult to forecast. Don't blame the Weather Bureau!
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