Antarctic atmospheric rivers set to double by the end of the century

Imagine a narrow, invisible firehouse stretching thousands of miles through the sky, carrying more water than the Amazon – meteorologists call these features atmospheric rivers. They form over warm oceans, sweep poleward, and unleash their cargo as intense rain or snow.

In the Arctic and mid-latitudes, these storms already shape flood and drought cycles. But over Antarctica – a continent that locks up enough ice to raise global seas by nearly 200 feet (60 meters) – their role has been harder to pin down.

A new study delivers the most detailed forecast of Antarctic atmospheric rivers to date. An international team led by Michelle Maclennan of the British Antarctic Survey analyzed a high-resolution climate model and a worst-case greenhouse-gas scenario.

The results suggest that the number of atmospheric rivers hitting Antarctica could double by 2100. The amount of moisture they deliver could also rise by two and a half times.

More moisture in a warmer world

The engine behind this change is simple physics: warmer air can hold more water vapor. As global temperatures climb, the Southern Ocean and lower atmosphere load up like a sponge.

The model uses 40 ensemble members to capture year-to-year swings. It shows an exponential rise in atmospheric moisture over Antarctic coastal waters. In some months late in the century, integrated water vapor could be three times higher than today’s values.

With more moisture available, the narrow jet-stream corridors that funnel air toward the pole become supersized rivers in the sky.

By applying present-day detection thresholds, the researchers find a continent-wide doubling of atmospheric-river days each year.

Even when the detection algorithm is “scaled” to account for the moister background (a tougher hurdle for qualifying as a river), certain hot-spot regions – especially Dronning Maud Land and parts of West Antarctica – still see clear increases.

Rain-snow tipping point

Antarctic atmospheric rivers are a mixed blessing for the ice sheet. Under cold conditions they produce heavy snowfall, adding mass and temporarily slowing sea-level rise.

Under warmer conditions they bring rain or above-zero air that can melt and weaken ice shelves – the floating ledges that buttress grounded glaciers. If those shelves fracture, inland ice can flow faster into the ocean.

Using surface-temperature criteria to separate snow from rain, the study reveals an intriguing twist. Rainfall will increase, but atmospheric rivers will mostly bring more snowfall to the ice sheet this century.

This could temporarily compensate for some of the mass that Antarctica loses elsewhere through ocean-driven melting and iceberg calving. Under the high-emissions pathway (known as SSP3-7.0), total atmospheric-river precipitation nearly triples, but most of that falls as snow.

Even so, rainfall spikes in vulnerable places like the Antarctic Peninsula and coastal ice shelves. The model suggests up to 40 millimeters of extra rain-water-equivalent each year on the Bellingshausen coast and Larsen C Ice Shelf.

Rain can soak porous firn, refreeze, and leave an ice lens that promotes further runoff and surface collapse – a process implicated in the disintegration of Larsen B in 2002.

Antarctic atmospheric rivers and sea-levels

One striking result is the sheer variability atmospheric rivers impose on Antarctica’s “surface mass balance,” the ledger of snow gained versus ice lost.

Today, a single storm offsets weeks of melting. In a warmer world, these storms grow larger and more frequent. Thus, yearly variations in atmospheric river frequency creates significant fluctuations in Antarctica’s contribution to sea-level rise, with that volatility appearing set to grow.

Because sea-level projections often rely on multi-decadal averages, this swing factor has been under-represented.

The new simulations indicate that by 2100, extreme-event years – those once considered rare – could become the norm. This shift would complicate efforts to forecast coastal risk for cities and small-island nations.

Wind shifts and ice loss

The model also captures how circulation changes amplify the story. As greenhouse forcing strengthens the temperature contrast between tropics and pole, the polar jet stream shifts eastward in segments and intensifies.

That wind realignment steers more atmospheric rivers toward the Amundsen Sea and Ross Sea sectors – regions already destabilized by warm ocean water undercutting ice shelves.

Meanwhile, sea-ice extent retreats, exposing open water that feeds extra moisture back into the storms. The authors warn that these coupled atmosphere–ice–ocean feedbacks could accelerate once thresholds are crossed.

Atmospheric rivers and climate predictions

“This is the first study to consider how these extreme weather events in Antarctica might change in response to human-induced warming this century,” Maclennan said.

“Because atmospheric rivers deliver massive precipitation to Antarctica and significantly impact snowfall variability, understanding their future patterns is crucial to projecting Antarctica’s contribution to sea level rise.”

Her team’s findings highlight a fresh source of uncertainty in global sea-level budgets. Most projections bracket the 21st-century rise between half and one meter. If Antarctic atmospheric rivers add more snow than rain, they could shave a few centimeters off the high end.

However, if warming outpaces snowfall gains, they could hasten ice-shelf collapse and push sea levels higher. Either way, policy planners need more precise tools that resolve these weather-driven swings.

Predictions of atmospheric rivers

The study emphasizes that predictions hinge on both emissions pathways and the technical choice of how researchers detect atmospheric rivers in models.

When adjusted for moister air, continent-wide doubling disappears. Instead, regional increases and decreases appear. This sensitivity highlights the need for multiple modelling approaches, finer-scale regional simulations, and continuous satellite monitoring.

Antarctica is sometimes portrayed as a silent, immutable block of ice. In reality it is poised to host ever-stronger that can both cushion and threaten the world’s coastlines.

Future research will determine which outcome dominates – but the message is clear: choices made this century about greenhouse-gas emissions will reverberate in every atmospheric river that sweeps across the coldest continent.

The study is published in the journal Nature Communications.

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