Exploring exogenous controls on short- versus long-term erosion rates globally

[摘要] Erosion is directly tied to landscape evolution throughthe relationship between sediment flux and vertical lowering of the landsurface. Therefore, the analysis of erosion rates across the planet measuredover different temporal domains may provide perspectives on the drivers andprocesses of land surface change over various timescales. Differentmetrics are commonly used to quantify erosion (or denudation) overtimescales of 10 1  years (suspended sediment flux) and 10 3 –10 6  years (cosmogenic radionuclides), meaning that reconciling potentiallycontrasting rates at these timescales at any location is challenging.Studies over the last several decades into erosion rates and their controlshave yielded valuable insights into geomorphic processes and landforms overtime and space, but many are focused at local or regional scales. Gaps remainin understanding large-scale patterns and exogenous drivers (climatic,anthropogenic, tectonic) of erosion across the globe. Here we leverage theexpanding availability and coverage of cosmogenic-derived erosion data andhistorical archives of suspended sediment yield to explore these controlsmore broadly and place them in the context of classical geomorphic theory.We make the following findings in this paper: (1) there are relationships between both long- and short-term erosion rates and mean annual precipitation, as well as aridity, similar to that proposed in classicgeomorphic literature on erosion; (2) agricultural activities have apparentlyincreased short-term erosion rates, outpacing natural drivers; (3) short-termerosion rates exceed long-term rates in all climatic regions except in mid- and high latitudes, where long-terms rates are higher due to the influenceof repeated glacial cycles; and (4) tectonically active margins have generallyhigher long-term erosion rates and apparently lower rainfall thresholds forerosion which potentially arise due to steeper slopes and associatedlandslides, overcoming vegetative root reinforcement. These resultshighlight the complex interplay of external controls on land surfaceprocesses and reinforce the view that timescale of observation may revealdifferent erosion rates and principal controls.

[学科分类] 土壤学