Unveiling the hidden snow dunes shaping Antarcticas frozen landscape
Sand dunes are a familiar sight along beaches and in deserts. While we know how regular sand dunes are formed, much less is known about dunes made of snow. In a new study, scientists have analysed the vast snow dunes across Antarctica ? reshaping our understanding of the continent's surface dynamics.
This research sheds light on the unexplored world of Antarctic snow dunes, offering a fresh perspective on the complex interactions between wind, snow and climate in one of Earth's harshest environments.
In the far south of our planet lies the largest desert in the world: Antarctica. This continent, swept by violent winds and covered in snow and ice, is home to dunes, like all deserts. But here, they are not made of sand.
Dunes in Antarctica are formed by interactions between snow and wind. Their shapes are reminiscent of sand dunes. Among the various types, some dunes are very elongated, kilometres long but are only a few dozen centimetres high compared to tens of metres for their sandy counterparts.
These long snow dunes are still poorly documented compared to the smaller dunes visible from the ground, or the very large megadunes discovered by remote sensing decades ago. Their formation, distribution and orientation remain unknown.
In a recent paper published in Nature Geoscience, a team led by a research team from Université Grenoble Alpes in France and the Institut de Physique du Globe de Paris, used satellite data, including Copernicus Sentinel-2 imagery, to identify and analyse snow dunes.
The research team analysed over 33,000 satellite images taken between 2018 and 2021, covering an area of approximately 7.5 million square kilometres, or 60% of the Antarctic continent. Their findings reveal that the dunes are primarily shaped by wind-driven snow transport and limited by a process known as snow sintering.
Sintering, which involves the bonding of snow particles through gradual ice bridge formation, plays a key role in determining the availability of snow particles for transport. In Antarctica's extreme conditions, this process slows down the movement of snow, allowing dunes to grow through elongation rather than accumulating in height like traditional sand dunes.
One of the study's most significant discoveries is the widespread prevalence of longitudinal dunes, which account for 61% of the formations observed. These dunes form under unidirectional wind regimes, where strong and consistent winds stretch the snow into long, narrow shapes.
This pattern was especially prominent in East Antarctica, where large stretches of dunes align with winds that rush down from the high interior toward the coasts.
Using the results of a theory developed for sand dunes, the dominance of longitudinal dunes points to a broader conclusion: snow availability in Antarctica is limited across much of the continent.
Even in coastal regions, where snowfall is relatively high, strong winds often erode and remove snow before it has a chance to accumulate, leading to the creation of elongated snow dunes rather than taller, more complex formations.
The discovery of these snow dunes has far-reaching implications for understanding Antarctica's surface mass balance, which measures the amount of snow accumulating versus snow lost through processes like sublimation ? where snow turns into vapour.
Since snow sintering limits how much snow can be moved by wind, this discovery suggests that more snow is being stored on the surface than previously thought. This also has implications for how we model ice sheet dynamics and predict changes in Antarctica's ice mass under future climate scenarios.
As global temperatures rise, the balance between snow accumulation, wind strength and temperature could shift, potentially altering the nature of these snow dunes. Warmer and windier conditions in the future might lead to changes in dune formation processes, which could influence snow distribution across the continent.
This study wouldn't have been possible without the data provided by the Sentinel-2 satellites, which captured detailed optical images of Antarctica's surface.
Sentinel-2's 10?15m resolution enabled the detection of snow dunes longer than 20 m, offering an unprecedented look at the landscape and revealing patterns that had previously been difficult to observe.
The recent launch of Sentinel-2C, the third Copernicus Sentinel-2 satellite, has further underscored the critical role of Sentinel-2 in Antarctic research. By ensuring continuity in high-resolution, frequent imaging, Sentinel-2C builds on the legacy of its predecessors ? enhancing the capabilities of the Copernicus program to support vital environmental monitoring.
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