Rain is rare in Antarctica. Scientists doing fieldwork there dress for cold and glare, not wet weather – duvet jackets, snow trousers, goggles and sunscreen. Planes land on gravel runways which are rarely icy, since there is no precipitation to freeze. Historic huts remain well preserved in the dry air.

But this is beginning to change.

Rain is already falling more frequently on the narrow and mountainous Antarctic Peninsula, the northernmost finger of the continent pointing towards South America. Already the warmest part of Antarctica, the Peninsula is warming faster than the rest of the continent, and far faster than the global average. It provides an advanced sign of what coastal Antarctica – especially the fragile West Antarctic Ice Sheet – may experience in the coming decades.

I recently led a team of scientists looking at how the Antarctic Peninsula will change this century under three scenarios: high, medium and low greenhouse gas emissions. We found that, as the peninsula warms, precipitation will rise slightly – and will increasingly fall as rain rather than snow. As days above 0°C become more common, this rainfall will fundamentally change the peninsula.

When heat and rain arrive together

Extreme weather is already causing disruption. A heatwave in February 2020 brought temperatures of 18.6°C to the northern peninsula – T-shirt weather, for almost the first time in recorded Antarctic history – while the “ice shelf” surface alongside melted at a record pace.

Atmospheric rivers – long, thin corridors of warm, moist air that start at warmer latitudes – are playing a growing role. In February 2022, one resulted in record surface melt. Another, in July 2023, brought rainfall and temperatures of +2.7°C to the peninsula in the depths of winter. These events are happening more often, delivering rain and melt to regions where neither had been observed before.

What rain does to snow and ice

Snow does not like rain. We’ve all sadly watched snowfall melt away particularly rapidly when it rains.

On the Antarctic Peninsula, rain brings heat and melts and washes away snow, stripping glaciers of their nourishment. Meltwater can also reach the bed of the glacier, lubricating its base and making glaciers slide faster. This increases iceberg calving and the rate of glacier mass loss into the ocean.

On floating ice shelves, rain compacts the snow that has fallen on the surface, meaning water starts forming ponds. This ponded meltwater then warms, as it is less reflective than the surrounding snow and ice, and can melt downwards through the ice shelf to the ocean below, weakening the ice and causing more icebergs to break off.

This can destabilise the ice shelf. Meltwater ponding has been implicated in the collapse of the Larsen A and B ice shelves in the early 2000s.

Sea ice is vulnerable too. Rain reduces snow cover and surface reflectivity, making the ice melt faster. Loss of sea ice also weakens the natural buffers that dampen ocean waves and help prevent the ends of glaciers snapping off and becoming icebergs. It also means less habitat for algae and krill, and reduces breeding platforms for penguins and seals.

Ecosystems under stress

A rainier climate will have a series of ecological impacts.

Water can flood penguin nest sites. Penguins evolved in a polar desert and aren’t adapted for rain. Their chicks’ fluffy feathers are not waterproof, so heavy rain drenches them, sometimes leading to hypothermia and death.

Together with a warming ocean, decreased sea ice and decreased krill, this pressure will affect penguins across the continent. Iconic Antarctic species such as ice-dependent Adélie and chinstrap penguins are at risk of being replaced as more adaptable gentoo penguins expand southwards.

Rainfall also alters life on smaller scales. When it strips away snow cover, it disrupts snow algae – microscopic plants that contribute to Antarctic land ecosystems. These algae feed microbes and tiny invertebrates and can darken the snow surface, increasing solar absorption and accelerating melt.

Snow normally insulates the ground, buffering temperature swings and protecting the organisms underneath. Exposed surfaces face harsher, more variable conditions.

At the same time, warming seas may make it easier for invasive marine species such as certain mussels or crabs to colonise the area.

Challenges for scientists

Humans are also not immune to the challenges posed by a rainier Antarctic Peninsula.

With increasing geopolitical interest, it is likely that human infrastructure will increase, with potential new settlements and bases to serve emerging industries such as tourism or krill fishing.

Research infrastructure was designed for snow, not sustained rainfall. Rain freezing on airstrips renders them unusable until the ice is melted. Slush and meltwater can damage buildings, tents, instruments and vehicles. Clothing and equipment may need to be redesigned.

Some entire research sites may have to move. On nearby Alexander Island, increased surface melt has already disrupted access to long-running ecological research at Mars Oasis – continuously studied since the late 1990s – resulting in gaps in the scientific record.

Heritage at risk

Historic sites are especially vulnerable.

Antarctica contains 92 designated historic sites and monuments, the result of two centuries of exploration and research. Many of these timber huts, equipment stores and early scientific installations are clustered on the peninsula.

In a warmer and wetter climate, thawing permafrost and heavier rainfall threaten the structural integrity of these sites. Timber will deteriorate faster. Foundations will sink. These sites will need more frequent maintenance, in a part of the world where conservation work is already logistically difficult.

The Antarctic Peninsula is already undergoing rapid change. If global warming moves towards 2°C or 3°C this century, extreme weather, rainfall and surface melt will intensify. Damage to ecosystems, infrastructure, glaciers and heritage sites could be severe and potentially irreversible.

Rain, once a rarity in Antarctica, is becoming a force capable of reshaping life on the peninsula. Limiting warming to below 1.5°C won’t prevent these changes entirely. But it could slow how quickly rainfall transforms the frozen continent.

Bethan Davies, Professor of Glaciology, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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