Sastrugi

Sastrugi are wind-shaped snow features, often elongated ridges separated by grooves. They develop as wind erodes, transports and redeposits snow, and are widespread on Antarctic snowfields. Their size and complexity vary with the snow surface and wind history. They are distinct from depositional snow dunes, although both are aeolian landforms: sastrugi are metre-scale erosional roughness features, while snow dunes can extend over much greater distances.

The long axes of sastrugi commonly align with the prevailing wind that shaped them, which makes their orientation useful as an indicator of near-surface airflow. The relationship is not a simple wind vane reading: a change in wind can alter the existing forms, and new features may take time to develop. Interpretation should account for the sequence and strength of winds, as well as the snow's erodibility.

Sastrugi are not merely passive marks on the surface. They increase aerodynamic roughness and contribute form drag, affecting turbulence and the wind field above snow. Observations during two erosion events in coastal Adélie Land found that when wind direction shifted about 20–30 degrees away from alignment with the existing sastrugi, measured drag increased and aeolian snow mass flux fell; strong, sustained winds could streamline the forms over a timescale as short as roughly three hours in those particular events. These measurements are site- and event-specific rather than universal constants.

Sastrugi can help researchers infer wind patterns, snow erosion and deposition, and surface conditions. Their irregular terrain can also make travel and field operations more difficult. In models of polar weather and snow transport, representing their changing roughness can matter because their drag depends on orientation and because the features themselves can be reshaped by the wind.