NASA imagery reveals Arctic sediment dynamics on Severny Island
Analysis of cone-shaped alluvial fans on Severny Island underscores the impact of glacial melt and seasonal runoff on Arctic terrain.
NASA’s Earth Observatory has published an analysis of Landsat 9 satellite imagery depicting alluvial fans on Severny Island, part of the Russian Novaya Zemlya archipelago in the Arctic. The report, which serves as the answer to a July Puzzler, describes the scene as an "alluvial face-off" where sediment eroded from ice-capped mountains splay out across a broad river valley.
Severny Island is a mountainous, uninhabited landmass in the high latitudes of the Northern Hemisphere, largely covered in glacial ice. On the southern end of the island, rivers rush down from rugged terrain flanking a broad valley. Upon reaching flatter ground, the waters slow and distribute sediment into cone-shaped features known as alluvial fans. Several of these fans appear in opposing orientations alongside a braided river in the captured imagery.
Alluvial fans typically form at the base of steep mountain ranges where narrow river channels open onto flatter terrain. In these locations, rivers can slow, divide into smaller channels, and deposit sediment. Over time, the channels migrate back and forth to build up these fan-shaped deposits. Dueling fans line several northwest-southeast-trending valleys in the wider view provided by the satellite data.
Seasonal snowmelt and glacial runoff likely keep Severny’s rivers supplied with ample fan-building material. Hydrologists note that higher river flows during the warmer months, driven by snowmelt, can carry more sediment out of the mountains. Glaciers also produce large volumes of eroded material as they grind downslope, some of which flushes out in meltwater.
Smaller, land-terminating mountain glaciers, like those on southern Severny Island, are particularly prone to melting as the atmosphere warms. Recent analyses incorporating digital elevation models found that land-terminating glaciers across the Novaya Zemlya archipelago thinned during the 2000s and 2010s, especially at lower elevations.
Severny’s ice is relatively understudied due to its remoteness, but satellite observations give scientists an understanding of its health. The imagery, created by Lauren Dauphin using Landsat data from the U.S. Geological Survey, provides key insights into the geological processes shaping this remote Arctic environment.
