Preprints
https://doi.org/10.5194/esurf-2021-20
https://doi.org/10.5194/esurf-2021-20

  13 Apr 2021

13 Apr 2021

Review status: this preprint is currently under review for the journal ESurf.

Effect of rock uplift and Milankovitch timescale variations in precipitation and vegetation cover on catchment erosion rates

Hemanti Sharma1, Todd A. Ehlers1, Christoph Glotzbach1, Manuel Schmid1, and Katja Tielbörger2 Hemanti Sharma et al.
  • 1Department of Geosciences, University of Tübingen, 72076 Tübingen, Germany
  • 2Department of Biology, Plant Ecology Group, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany

Abstract. Catchment erosion and sedimentation are influenced by variations in the rates of rock uplift (tectonics), and periodic fluctuations in climate and vegetation cover. In this study we applied the Landlab-SPACE landscape evolution modelling approach. This study focuses on quantifying the effects changing climate and vegetation on erosion and sedimentation over distinct climate-vegetation settings. As catchment evolution is subjected to tectonic and climate forcings at millennial to million-year time-scales, the simulations are performed over different tectonic scenarios and periodicities of climate-vegetation change. We present a series of generalized experiments that explore the sensitivity of catchment hillslope and fluvial erosion and sedimentation for different rock uplift rates (0.05 mm a−1, 0.1 mm a−1, 0.2 mm a−1) and Milankovitch climate periodicities (23 kyr, 41 kyr 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 analysed 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. While 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 climatic conditions, which is beyond the scope of this study. These effects being most pronounced over longer period changes (100 kyr) and higher rock uplift rates (0.2 mm yr−1). This holds true for both vegetation and climate settings. Furthermore, transient changes in catchment erosion due to varying vegetation and precipitation were between ~35 %–110 % of the background (rock uplift) rate and are measureable with some 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.

Hemanti Sharma et al.

Status: open (until 25 May 2021)

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Hemanti Sharma et al.

Hemanti Sharma et al.

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Short summary
We study effects of variable climate-vegetation with different uplift rates on erosion-sedimentation using landscape evolution modeling approach. Results suggest that regardless of uplift rates, transients in precipitation-vegetation leads to transients in erosion rates in same direction of change. We conclude that vegetation-dependent erosion and sedimentation are influenced by Milankovitch timescale changes in climate but these transients are superimposed upon tectonically driven uplift rates.