Topographic Asymmetry Across the Arctic. Issue 17 (8th September 2021)

• Record Type: Journal Article
• Authors: Zwieback, Simon
• Is Part Of: Geophysical research letters. Volume 48:Issue 17(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-08
• Subjects: Climate sensitivity -- hillslope -- permafrost -- topography; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094895
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Aspect‐dependent differences in steepness provide insight into the fate and formation of permafrost‐affected landscapes, but the circum‐Arctic distribution of topographic asymmetry remains unknown. The maps derived here add nuance to the notion that periglacial conditions promote steeper north‐facing slopes. Only 20% of the area exhibits elevated north–south asymmetry, chiefly in rugged terrain. Across all moderate‐relief landscapes, there is a bell‐shaped trend with temperature. Steeper south‐facing slopes are common in very cold and cool regions. In between, steeper north‐facing slopes predominate. Despite multiple caveats, the bell‐shaped trend with temperature suggests controls that vary with climatic factors, including permafrost conditions. The bell‐shaped trend and observations of permafrost degradation further indicate that certain asymmetric transition‐zone landscapes are predisposed to enhanced geomorphic activity in a warming climate. Plain Language Summary: For centuries, it has been noted that in some Arctic landscapes the steepness of hillslopes varies systematically with direction. The north‐facing slopes are often steeper. They are also colder because they receive less sunlight. The warmer south‐facing hillslopes are thought to be gentler because deeper thaw promotes soil transport. However, we do not know how widespread such asymmetry is. Analyzing a circum‐Artic topographic data set, we find that only 20% of the area is clearly asymmetric. Elevated asymmetry is largely confined to rugged landscapes. Across landscapes with moderate relief, we find that asymmetry varies systematically with temperature. In the coldest areas, south‐facing slopes are steeper on average. In cold landscapes with a mean temperature of about −10°C, the north‐facing slopes are steeper, while in cool regions (about 0°C), the south‐facing slopes are slightly steeper on average. Because asymmetry changes systematically with temperature, climate warming can plausibly stimulate terrain instability and reorganization. For instance, we document (steeper) north‐facing slopes in cold‐to‐cool regions becoming unstable as previously frozen soil thaws, potentially compromising infrastructure and water resources. Key Points: In the High Arctic, south‐facing slopes are steeper on average Steeper north‐facing slopes prevail in the Low Arctic and Subarctic The dependence of asymmetry on temperature may stimulate enhanced geomorphic change with warming