World Water Day

Last weekend was World Water Day and the theme for 2025 is “Glacier Preservation.” At first glance, the theme seems irrelevant to the Caribbean. Most of us in the region don’t often think about the coldest regions of the planet – they’re thousands of miles away after all – but we really should, as their demise signals massive problems for small islands like ours.

The cryosphere – from the Greek word “krios” meaning cold – refers to the surfaces of the Earth that are covered in snow or ice and, for at least a large part of the year, have temperatures below 0°C. One part of the cryosphere is ice found in water, like the frozen parts of the ocean around Antarctica and the Arctic. The other part of the cryosphere includes ice and snow on land (like the continental ice sheets in Greenland and Antarctica), glaciers, ice caps and areas of permafrost.

And while most of us are familiar with snow and glaciers (from photos, at least) permafrost is not as familiar to us as it should be. Permafrost is made up of soil, sand, sediment, or rock (usually bound together by ice) that has remained frozen at or below 0°C for at least two years in a row.  But it’s more than just a layer of rocks and ice; it has also served as an incredible carbon sink. Large amounts of organic carbon, accumulated over thousands of years, are trapped in the frozen layers of permafrost. The cold, stable conditions slow down microbial activity, which limits the breakdown of organic matter. As a result, carbon in the form of plant and animal remains is preserved in the frozen soil.

Melting permafrost in Norway

The Permafrost

The Arctic permafrost currently stores nearly 1,700 billion metric tons of frozen and thawing carbon – nearly twice the amount of greenhouse gases in the atmosphere right now. But thanks to climate change, the permafrost is thawing, and stored carbon is being released into the atmosphere as carbon dioxide (CO₂ – a heat-trapping gas, also known as a greenhouse gas) and methane. And even though methane is short-lived in the atmosphere compared to CO₂, it’s about 120 times more efficient at trapping heat. More heat trapped in the atmosphere means more permafrost could be lost, adding more dangerous greenhouse gases to the atmosphere, causing more warming and more melting permafrost. This is known as a positive feedback loop or, in plain language, a vicious cycle.

So why should we care about permafrost and glaciers when the only ice we need in the tropics is in our freezers and our drinks?  It turns out that all the frozen parts of the planet – the cryosphere – are intricately linked to the Earth’s other systems: the atmosphere, the land masses and the oceans. And since most of us in the Caribbean live at or near the ocean’s edge, we need to understand the impacts of a warming cryosphere on these related systems.

In the Arctic, vast expanses of bright white snow and ice reflect solar radiation back into space and help to regulate the Earth’s land and sea temperatures. But over the last 40-50 years, the extent of this ice has shrunk by about 40%. As more ice disappears, more dark ocean surface is exposed. As glaciers melt and recede, more land that was previously under the ice is exposed (for a fascinating look at a melting glacier check out this video). And just as the surface of an asphalt parking lot is hotter than the hood of your white car, the open (dark) water and land absorb the sun’s radiation and release the heat to the atmosphere, causing more global warming, which causes even more ice to melt. It’s yet another positive feedback loop. And we probably don’t need reminding that warmer oceans mean more extreme weather events, including more intense hurricanes, as we know only too well from experience.

Impacts in the Caribbean

But it doesn’t end there. All this melting ice has to go somewhere and, generally speaking, that somewhere is the ocean. So as more (previously landlocked) glaciers and ice caps melt into the ocean, sea levels rise. This has several direct impacts on communities around the Caribbean including coastal erosion and land loss, flooding, intrusion of salt water into freshwater aquifers, and damage to coastal ecosystems such as mangroves and coral reefs (both of which protect our shorelines).

In the Antarctic (which is about the size of the USA) there is a large ice sheet cover that helps to regulate atmospheric and oceanographic systems. Currently, climate scientists are unable to quantify the extent to which sea levels would rise globally if there were to be widespread melting of landlocked Antarctic ice sheets, although it’s expected to be in the range of metres.

Rising sea levels can also cause damage to roads, ports, and other infrastructure near the coast. This can be seen in places like Bermuda, where a detailed climate change study carried out by our team showed that even modest sea level rise threatens the major commercial centres of Hamilton and St. George’s, the country’s correctional facility, various marine terminals and piers, low-lying coastal roads, the airport, historical sites, and other infrastructure.

Melted ice flowing into a salty ocean causes changes to salinity levels, disrupting the fragile balance of marine ecosystems and impacting Caribbean fishing industries and our food security. It also impacts established ocean circulation patterns of warm surface currents and deep cold water currents, thereby influencing long-term climate trends and regional weather patterns (extreme heat, drought, intense rainfall, etc).

Rising sea levels can threaten the very existence of a country. At its highest point, the Republic of the Marshall Islands is just two metres above sea level. The people of this small island state face an existential threat from sea level rise as increasing salinity in soils and groundwater has led to crop damage and food insecurity. A 1-metre sea level rise will leave 40% of the buildings in its capital city under water, and whole islands in that chain will disappear. The population of an entire country will be forced to migrate, leading to major economic and social instability.

Majuro, Republic of Marshall Islands

So even though glaciers and permafrost and snowy peaks are a world away from the clear warm waters of the Caribbean, their loss will have ripple effects around the world, and we will definitely feel them in the Caribbean.