Antarctica receives snowfall, but far less than most people imagine. The interior of the continent gets roughly the same amount of annual precipitation as the Sahara Desert, which is why scientists classify much of Antarctica as a polar desert. The twist is that what little snow does fall almost never melts, so it has piled up over millions of years into an ice sheet averaging more than two kilometers thick. Understanding how snow arrives, where it goes, and why so little of it accumulates in some places reveals a continent that is far more dynamic than a featureless white expanse.
What Makes Antarctica a Desert
A desert is defined by how little precipitation a place receives, not by how hot it is. Most of Antarctica’s interior gets fewer than 50 millimeters of water-equivalent precipitation per year. For comparison, that is less than many of the driest spots in the American Southwest. The coast is wetter, with some areas receiving several hundred millimeters annually, but averaged across the continent the numbers are strikingly low. The reason is straightforward: cold air holds very little moisture. At the temperatures common on the high East Antarctic Plateau, which regularly drop below −40 °C in winter and can plunge past −80 °C, the atmosphere is almost completely wrung dry.
This creates a paradox that confuses people. Antarctica holds about 70 percent of the world’s fresh water locked in ice, yet it is one of the driest places on Earth in terms of new moisture arriving each year. The ice is ancient, built grain by grain over tens of millions of years. The extremely low temperatures prevent melting, so even tiny annual additions compound over geologic time into a colossal ice sheet. Think of it as a bank account with minuscule deposits and zero withdrawals running for eons.
How Snow Gets to Antarctica
Most Antarctic snowfall is delivered by weather systems that pull moist air from the Southern Ocean toward the continent. The most dramatic of these are atmospheric rivers, narrow corridors of concentrated water vapor that stretch from subtropical or mid-latitude regions all the way to the ice sheet. These events are rare at any given location, but they punch well above their weight. Atmospheric rivers have been responsible for the majority of extreme snowfall events in East Antarctica since the 1980s, and they contribute substantially to total precipitation, especially at elevations below about 3,000 meters.1PubMed Central. Contribution of Atmospheric Rivers to Antarctic Precipitation
These atmospheric rivers form within large-amplitude pressure patterns, often triggered by tropical convection thousands of kilometers away. When one of these moisture plumes reaches Antarctica, it can dump heavy snow on the coast and penetrate surprisingly far inland. The same events also carry heat, which can cause surface melting on coastal ice and even destabilize ice shelves.2Nature Reviews Earth & Environment. Atmospheric rivers in Antarctica So the mechanism that delivers Antarctica’s biggest snowfalls is also capable of destroying ice, a duality that matters enormously for the continent’s overall mass balance.
Outside of these dramatic events, snowfall comes from more ordinary cyclonic storms that circle the Southern Ocean. These contribute a steadier but lighter supply of moisture. In West Antarctica, atmospheric rivers are a primary driver of the most extreme snowfall and surface melting events alike.3The Cryosphere. Climatology and surface impacts of atmospheric rivers on West Antarctica The distinction between the two halves of the continent is important: West Antarctica sits at lower elevations and closer to the ocean, so it intercepts more moisture. East Antarctica, home to the high plateau, is drier and colder, and depends more heavily on rare large-scale weather events to get any precipitation at all.
Diamond Dust and Clear-Sky Precipitation
On the high interior plateau, something strange happens: it can snow without a cloud in sight. This phenomenon, called clear-sky precipitation or “diamond dust,” occurs when the air near the surface becomes supersaturated with water vapor. Tiny ice crystals nucleate directly in the boundary layer and drift slowly to the ground, glittering in the sunlight. Over the East Antarctic Plateau, clear-sky precipitation accounts for a significant fraction of total annual precipitation.4Journal of Geophysical Research: Atmospheres. ICESat‐2 Lidar Estimates of Clear‐Sky Precipitation Over the East Antarctic Plateau
Diamond dust crystals are extremely small, and observations at Dome C, one of the highest and coldest points on the plateau, show that these particles are predominantly irregular or columnar in shape rather than the classic hexagonal plate that most people picture when they think of a snowflake.5Atmospheric Chemistry and Physics. Unique microphysical properties of small boundary layer ice particles under pristine conditions on Dome C, Antarctica The crystals form at such low temperatures and with so little available moisture that they never develop into the elaborate branching structures associated with warmer snowfall. Researchers studying the genesis of diamond dust at Dome C have found that these episodes are linked to air masses with continental origins, whereas thicker cloud and precipitation events trace back to oceanic moisture.6Atmospheric Chemistry and Physics. Genesis of diamond dust, ice fog and thick cloud episodes observed and modelled above Dome C, Antarctica
If you stood at the South Pole on a calm, clear winter day, you could see diamond dust sparkling in the beam of a headlamp. It barely registers on a precipitation gauge, but in a place where almost nothing else falls from the sky for much of the year, it adds up.
Snow That Never Reaches the Ground
Not all precipitation that forms over Antarctica actually makes it to the surface. Along the coast, dry katabatic winds, gravity-driven flows of cold air racing downhill from the interior, create a layer of extremely dry air near the ground. Snow falling through this layer can sublimate before it lands, a phenomenon known as virga. Research along coastal Adélie Land has shown that this low-level sublimation considerably reduces the amount of water that reaches the surface.7The Cryosphere. Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adélie Land in Antarctica
The scale of this effect is larger than you might expect. Analysis combining ground-based observations and atmospheric models found that low-level sublimation reduces total continent-wide snowfall by about 17 percent, and by up to 35 percent along the margins of East Antarctica.8PubMed Central. Katabatic winds diminish precipitation contribution to the Antarctic ice mass balance That is a substantial fraction of already-meager precipitation simply vanishing into thin air on its way down. Satellite instruments that estimate snowfall from space typically cannot see this process, which means they tend to overestimate how much snow actually accumulates on the surface.
Where the Wind Takes the Snow
Even snow that successfully reaches the ground is not guaranteed to stay put. Antarctica is the windiest continent on Earth, and katabatic winds routinely pick up freshly fallen snow and transport it elsewhere. At one observation site in East Antarctica, roughly 38 percent of snowfall events did not result in any net accumulation because the wind ablated the fresh snow during or immediately after the event.9The Cryosphere. How does the ice sheet surface mass balance relate to snowfall? Insights from a ground-based precipitation radar in East Antarctica The snow is either launched back into the atmosphere, where it sublimates, or blown downhill and redeposited somewhere else entirely.
This wind redistribution creates dramatic contrasts. Sheltered valleys and leeward slopes can accumulate deep snowdrifts, while windward ridges and slopes are scoured down to bare blue ice. Across the continent, an estimated 2.7 to 6.6 percent of Antarctica’s surface area has persistent negative net accumulation from wind scour alone, meaning the wind removes more snow than falls in those zones.10Nature Geoscience. Influence of persistent wind scour on the surface mass balance of Antarctica These scour zones are predominantly in East Antarctica, and they are controlled by bedrock topography underneath the ice, which steepens surface slopes and accelerates the wind in predictable patterns. Katabatic winds near grounding zones further erode and sublimate snow, shaping the ice surface in ways that persist over long timescales.11Earth and Planetary Science Letters. Katabatic and foehn winds control the distribution of supraglacial lakes in Dronning Maud Land, Antarctica
The net result of wind erosion across the entire continent is that present surface mass balance calculations may overestimate the snow input by 11 to 36.5 billion metric tons per year.10Nature Geoscience. Influence of persistent wind scour on the surface mass balance of Antarctica That discrepancy matters when scientists try to figure out whether Antarctica is gaining or losing ice overall.
The McMurdo Dry Valleys
The most extreme expression of Antarctic aridity is the McMurdo Dry Valleys in East Antarctica, a region of bare rock, gravel, and ice-free soil that looks more like Mars than anything else on Earth. Some of these valleys receive fewer than 10 millimeters of water-equivalent precipitation per year, and what little snow does accumulate vanishes rapidly. Observations around the major lakes in the Dry Valleys show that seasonal snow cover can shrink by more than 90 percent between peak accumulation in October and mid-January, driven by a combination of sublimation, wind scour, and limited melt.12Hydrological Processes. Spatial and temporal patterns of snow accumulation and aerial ablation across the McMurdo Dry Valleys, Antarctica
Beneath the surface of these valleys, ice persists in the soil as “ice cement.” Modeling of Victoria Valley suggests this buried ice sublimates at a rate of about 0.22 millimeters per year, with the ice boundary slowly descending about 1.2 millimeters per year. In summer, any snow cover can briefly reverse the vapor transport and slow the loss, but the ice is steadily retreating.13Journal of Geophysical Research: Earth Surface. Sublimation and ice condensation in hyperarid soils: Modeling results using field data from Victoria Valley, Antarctica The Dry Valleys are a vivid reminder that “polar desert” is not a metaphor. These are genuinely arid landscapes where water is the limiting resource, just as it is in hot deserts.
Why Measuring Antarctic Snowfall Is So Difficult
Getting accurate precipitation numbers for Antarctica is surprisingly hard. You cannot just set out rain gauges across a continent where wind-driven snow makes it impossible to tell the difference between falling snow and blowing snow. Ground-based precipitation radars can distinguish overhead snowfall from surface drifting, but they exist at only a handful of stations.
The main tool for continent-wide snowfall estimates has been the CloudSat satellite, which carries a radar that can detect snow from orbit. But CloudSat’s radar has a blind zone near the surface, and studies have shown that this leads to underestimation of precipitation by roughly 9 to 11 percentage points.14Journal of Geophysical Research: Atmospheres. How does the spaceborne radar blind zone affect derived surface snowfall statistics in polar regions? On top of that, the satellite passes over any given location only every few days, so it can miss entire storms. Evaluations comparing CloudSat with ground-based radars have found large uncertainties in total snowfall amounts, with estimates at some stations ranging from roughly 55 percent below to 45 percent above the true value depending on how the satellite sampling happened to line up with storm timing.15The Cryosphere. Evaluation of the CloudSat surface snowfall product over Antarctica using ground-based precipitation radars Atmospheric reanalysis products fill some of the gaps, and recent comparisons show that several reanalyses reproduce the large-scale spatial and seasonal snowfall patterns reasonably well, but significant disagreements remain at regional and local scales.16Earth and Space Science. Antarctic Snowfall Patterns and Trends: A Regional Analysis Across Multiple Data Sets
The measurement problem is not just academic. Every estimate of Antarctica’s contribution to sea-level change depends on knowing how much snow goes in versus how much ice flows out. Errors in snowfall estimates propagate directly into the mass-balance calculations that inform climate projections.
Is Antarctic Snowfall Changing
Over the twentieth century, Antarctic snowfall appears to have increased. Ice core records and modeling suggest that growing precipitation over the ice sheet partially offset sea-level rise during that period, though the magnitude is debated. One analysis found that a warming atmosphere cannot be excluded as a major driver of the underlying increase.17Nature Climate Change. Increased snowfall over the Antarctic Ice Sheet mitigated twentieth-century sea-level rise The logic is simple: warmer air holds more moisture, so as the Southern Ocean and lower atmosphere warm, more water vapor is available to be transported to Antarctica and deposited as snow.
The picture gets more complicated when you look at regional patterns. Ice core measurements reveal a dipole trend in West Antarctica over the past century: snow accumulation increased by more than 2,000 billion metric tons over the Antarctic Peninsula and Ellsworth Land, while it decreased by about 500 billion metric tons over Marie Byrd Land.18PubMed Central. Century-long West Antarctic snow accumulation changes induced by tropical teleconnections These opposing trends are linked to shifts in atmospheric circulation driven by tropical climate variability, not simply by local warming. Meanwhile, coherent positive snowfall trends have been observed across East Antarctica in multiple data sets.
Modeling of future snowfall suggests that the dominant driver of changes will be synoptic-scale weather events, essentially storms, rather than shifts in the continent’s large-scale mean circulation. In East Antarctica, the large-scale atmospheric circulation actually works against accumulation, tending to transport moisture away from the region; it is the individual storms that deliver the snow.19Communications Earth & Environment. Future Antarctic snow accumulation trend is dominated by atmospheric synoptic-scale events Whether atmospheric rivers become more frequent or more intense in a warming climate could be one of the biggest wildcards for Antarctica’s future snowfall.
Snowfall, Ice Mass, and Sea Level
The reason snowfall trends matter so much is their direct connection to global sea level. If Antarctica gains more mass from snow than it loses from ice discharge into the ocean, the ice sheet acts as a brake on sea-level rise. Satellite radar altimetry showed that the interior of the East Antarctic ice sheet gained about 45 billion metric tons per year between 1992 and 2003, a rate sufficient to slow sea-level rise by roughly 0.12 millimeters per year.20PubMed. Snowfall-driven growth in East Antarctic ice sheet mitigates recent sea-level rise That gain was linked to increased precipitation.
But East Antarctica’s gains have been more than counterbalanced in recent decades by accelerating ice loss from West Antarctica and the Antarctic Peninsula, where warming ocean water is melting ice shelves from below, speeding up glacier flow. The net effect for the whole continent has shifted toward ice loss, meaning Antarctica is now contributing to sea-level rise rather than opposing it. Increased snowfall in the interior provides some buffer, but it is being outpaced by ice dynamics at the margins. The interplay between these two forces, more snow coming in versus more ice going out, is one of the biggest open questions in climate science.
Life in a Polar Desert
Despite the extreme aridity, Antarctica is not lifeless. Mosses, lichens, and microbial communities survive in microclimates where just enough meltwater, protection from wind, and nutrients (often from seabird colonies) converge.21PubMed Central. Basking in the sun: how mosses photosynthesise and survive in Antarctica These organisms depend on snow and ice as their water source, which makes them exquisitely sensitive to any changes in when and where snow accumulates. A spot that loses its seasonal snow cover, or gains too much and stays buried past the brief growing season, can shift from habitable to barren within a few years.
The Dry Valleys host some of the most extreme microbial ecosystems on Earth, with bacteria living inside porous rocks (endoliths) and algae surviving in permanently ice-covered lakes. For these organisms, the tiny amount of snow and ice melt that penetrates cracks in rock or percolates through thin soils is the entire hydrological cycle. Researchers studying these communities often draw parallels to the conditions that might exist or have existed on Mars, where buried ice and hyperarid soils pose similar challenges to any potential biology. Buried snowpack deposits in Antarctic polar desert valleys have been specifically proposed as analogues for similar features observed on Mars, including at the Phoenix landing site.22Antarctic Science. Formation and evolution of buried snowpack deposits in Pearse Valley, Antarctica, and implications for Mars
The convergence of Antarctic and planetary science is not a coincidence. Antarctica’s polar desert is the closest thing Earth offers to the surface conditions of another planet, making it a natural testing ground for instruments, survival strategies, and hypotheses about extraterrestrial ice and water. For scientists who study Mars, a field season in the Dry Valleys is the next best thing to actually going there.