Abstract

Abstract. Catchment erosion and sedimentation are influenced by variations in the rates of rock uplift (tectonics) and periodic fluctuations in climate and vegetation cover. This study focuses on quantifying the effects of changing climate and vegetation on erosion and sedimentation over distinct climate–vegetation settings by applying the Landlab–SPACE landscape evolution model. As catchment evolution is subjected to tectonic and climate forcings at millennial to million-year timescales, the simulations are performed for different tectonic scenarios and periodicities in climate–vegetation change. We present a series of generalized experiments that explore the sensitivity of catchment hillslope and fluvial erosion as well as sedimentation for different rock uplift rates (0.05, 0.1, 0.2 mm a−1) and Milankovitch climate periodicities (23, 41, and 100 kyr). Model inputs were parameterized for two different climate and vegetation conditions at two sites in the Chilean Coastal Cordillera at ∼26∘ S (arid and sparsely vegetated) and ∼33∘ S (Mediterranean). For each setting, steady-state topographies were produced for each uplift rate before introducing periodic variations in precipitation and vegetation cover. Following this, the sensitivity of these landscapes was analyzed for 3 Myr in a transient state. Results suggest that regardless of the uplift rate, transients in precipitation and vegetation cover resulted in transients in erosion rates in the direction of change in precipitation and vegetation. The transients in sedimentation were observed to be in the opposite direction of change in the precipitation and vegetation cover, with phase lags of ∼1.5–2.5 kyr. These phase lags can be attributed to the changes in plant functional type (PFT) distribution induced by the changes in climate and the regolith production rate. These effects are most pronounced over longer-period changes (100 kyr) and higher rock uplift rates (0.2 mm yr−1). This holds true for both the vegetation and climate settings considered. Furthermore, transient changes in catchment erosion due to varying vegetation and precipitation were between ∼35 % and 110 % of the background (rock uplift) rate and would be measurable with commonly used techniques (e.g., sediment flux histories, cosmogenic nuclides). Taken together, we find that vegetation-dependent erosion and sedimentation are influenced by Milankovitch timescale changes in climate but that these transient changes are superimposed upon tectonically driven rates of rock uplift.

Highlights

  • The pioneering work of Grove Karl Gilbert (Gilbert, 1877) highlighted the fact that surface uplift, climate, and biota jointly influence catchment-scale rates of weathering and erosion

  • This study focuses on quantifying the effects of changing climate and vegetation on erosion and sedimentation over distinct climate–vegetation settings by applying the Landlab–SPACE landscape evolution model

  • These phase lags can be attributed to the changes in plant functional type (PFT) distribution induced by the changes in climate and the regolith production rate

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Summary

Introduction

The pioneering work of Grove Karl Gilbert (Gilbert, 1877) highlighted the fact that surface uplift, climate, and biota (amongst other things) jointly influence catchment-scale rates of weathering and erosion. Several studies have documented how the combined effects of either climate and vegetation change or variable rates of rock uplift and climate change (including glaciation) impact catchment-scale processes (Herman et al, 2010; Mishra et al, 2019; Schmid et al, 2018; Tucker, 2004; Yanites and Ehlers, 2012). Previous studies have found that the long-term development of topography (such as over million-year timescales) is in many situations sensitive to the tectonic, climate, and vegetation history of the region and that competing effects of different coeval processes (e.g., climate change and tectonics) exist but are not well understood

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