Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia

Glacial landscapes are characterized by dramatic local relief, but they also commonly exhibit high-elevation, low-relief surfaces(1-7). These surfaces have been attributed to glacial headward erosion in Alpine settings(1,2). However, the timing and processes responsible for their formation in northern high-latitude regions remain elusive(4,7). Here we estimate the rate of fjord erosion from geophysical relief(8,9) and compare that with the erosion reflected by offshore sedimentation in western Scandinavia during the late Pliocene and Quaternary glaciations (0-2.8 million years ago). We find that the sediments generated by fjord erosion over the entire western Scandinavia accounts for only 35-55% of the total sediment volume deposited off the coast of Norway. This large mismatch implies that during this period, significant erosion must have also taken place away from the fjords at high elevation and indicates a bimodal distribution of glacial erosion(10). Furthermore, comparing the distribution of the high-elevation, low-relief surfaces with estimates of the long-term glacier equilibrium line altitude supports the idea that effective erosion in extensively glaciated areas limits topographic height, a process known as the glacial buzzsaw(2,6,11,12). We therefore conclude that glacial and periglacial processes have a substantial impact on the formation of low-relief surfaces observed(1-7) in glaciated mountain belts and high-latitude continental margins.