Peatlands characterized by polygonal mounds are a common and often highly stable feature of the Arctic coast, despite significant environmental change elsewhere in the region. Measurements of surface albedo and heat flux suggest that local feedbacks contribute to the stability of these systems.
John Gamon of the University of Alberta and colleagues studied the surface properties of a polygonal peat plateau in Manitoba to determine the source of its stability. The troughs of standing water surrounding the polygonal mounds are typically dominated by sedges, whereas the mounds are dominated by dwarf shrubs and lichens. During the summer, the troughs have a lower albedo, and consequently gain more heat and thaw to a greater depth than the mounds. During winter, a deeper snowpack forms over the troughs, helping to retain some of the summer heat. As a result, the troughs exhibit substantially higher annual surface temperatures, on average, than the mounds.
The researchers suggest that the contrasting thermal regimes exhibited by the troughs and mounds reinforce these structural features, and thereby help to stabilize this patterned landscape.