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

Abstract

Erosion is directly tied to landscape evolution through the relationship between sediment flux and vertical lowering of the land surface. Therefore, the analysis of erosion rates across the planet measured over different temporal domains may provide perspectives on the drivers and processes of land surface change over various timescales. Different metrics are commonly used to quantify erosion (or denudation) over timescales of <101 years (suspended sediment flux) and 103-106 years (cosmogenic radionuclides), meaning that reconciling potentially contrasting rates at these timescales at any location is challenging. Studies over the last several decades into erosion rates and their controls have yielded valuable insights into geomorphic processes and landforms over time and space, but many are focused at local or regional scales. Gaps remain in understanding large-scale patterns and exogenous drivers (climatic, anthropogenic, tectonic) of erosion across the globe. Here we leverage the expanding availability and coverage of cosmogenic-derived erosion data and historical archives of suspended sediment yield to explore these controls more 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 classic geomorphic literature on erosion; (2) agricultural activities have apparently increased short-term erosion rates, outpacing natural drivers; (3) short-term erosion rates exceed long-term rates in all climatic regions except in mid- and high latitudes, where long-terms rates are higher due to the influence of repeated glacial cycles; and (4) tectonically active margins have generally higher long-term erosion rates and apparently lower rainfall thresholds for erosion which potentially arise due to steeper slopes and associated landslides, overcoming vegetative root reinforcement. These results highlight the complex interplay of external controls on land surface processes and reinforce the view that timescale of observation may reveal different erosion rates and principal controls.