Iceworld Update: Hidden Snow Dunes in Antarctica

Sand dunes are a familiar sight on beaches and deserts. While we know how regular sand dunes form, much less is known about dunes made from snow. In a new study, scientists have analyzed Antarctica's giant snow dunes, changing our understanding of the continent's surface dynamics.

This research sheds light on the unexplored world of Antarctic snow dunes and offers a new perspective on the complex interactions between wind, snow and climate in one of the harshest environments on Earth.

In the very south of our planet lies the largest desert in the world: Antarctica. Like all deserts, this continent, hit by strong winds and covered in snow and ice, has dunes. 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, kilometers long, but only a few tens of centimeters high, compared to several tens of meters for their sandy counterparts.

These long snow dunes remain poorly documented compared to the smaller dunes visible from the ground or the very large megadunes discovered by remote sensing decades ago. Their origin, distribution and orientation remain unknown.

In a recent paper published in Nature Geoscience, a team led by a team of researchers from Université Grenoble Alpes in France and the Institut de Physique du Globe de Paris used satellite data, including images from Copernicus Sentinel-2, to identify and analyze snow dunes.

The research team analyzed over 33,000 satellite images taken between 2018 and 2021, covering an area of ​​about 7.5 million square kilometers, or 60% of the Antarctic continent. Their results show that the dunes are formed primarily by wind-driven snow transport and are limited by a process known as snow sintering.

Longitudinal snow dunes in Antarctica – ESA Larger image

Sintering, where snow particles are bonded together through the gradual formation of ice bridges, plays a key role in determining the availability of snow particles for transportation. In Antarctica's extreme conditions, this process slows the movement of snow, allowing the dunes to grow by stretching rather than accumulating in height like traditional sand dunes.

One of the study's most significant discoveries is the widespread distribution of longitudinal dunes, which account for 61% of the observed formations. These dunes form in unidirectional wind conditions, where strong and consistent winds stretch the snow into long, narrow shapes.

This pattern was particularly pronounced in East Antarctica, where large stretches of dunes are aligned with winds flowing down from the high interior towards the coasts.

Based on the results of a theory developed for sand dunes, the dominance of longitudinal dunes allows for 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 the snow and carry it away before it can accumulate. This creates 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 that accumulates versus snow that is lost through processes such as sublimation – where snow is converted into vapor.

Since snow sintering limits how much snow can be moved by the 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 speed and temperature could shift, potentially changing the nature of these snow dunes. In the future, warmer and windier conditions could lead to changes in dune formation processes that could affect snow distribution across the continent.

This study would not have been possible without the data from the Sentinel-2 satellites, which captured detailed optical images of the surface of Antarctica.

Sentinel-2's 10-15 m resolution enabled the detection of snow dunes longer than 20 m, providing an unprecedented view of the landscape and revealing patterns that were previously difficult to observe.

The recent launch of Sentinel-2C, the third Copernicus Sentinel-2 satellite, has further highlighted Sentinel-2's critical role in Antarctic research. By ensuring continuity in high-resolution, frequent imaging, Sentinel-2C builds on the legacy of its predecessors and expands the Copernicus program's capabilities to support critical environmental monitoring.

Astrobiology