Research ArticleGEOPHYSICS

Climate controls on erosion in tectonically active landscapes

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Science Advances  16 Oct 2020:
Vol. 6, no. 42, eaaz3166
DOI: 10.1126/sciadv.aaz3166
  • Fig. 1 Topography, erosion, and precipitation in the Bhutan Himalaya.

    (A) Digital elevation model overlaid by new and previously published cosmogenic nuclide, basin-averaged erosion rates (1315). Black line denotes the border of Bhutan (see inset). (B) Mean annual rainfall (R) data (43) overlaid by channel steepness (ksn) data.

  • Fig. 2 Best-fit relationships between channel steepness (ksn) and erosion rate for different rainfall bins.

    In all plots, the solid black and gray curves denote relationships as calculated by the least-squares estimation regression using a fixed and free exponent (n), respectively. The dashed gray curve is the solution for the stream-power model (Eq. 1b) given the rainfall bin centers, and a Klp value of 2.2 × 10−9 m−2. (A) Basins that receive less than 1.5 m year−1 annual rainfall. (B) Basins that receive between 1.5 and 2.5 m year−1. (C) Basins that receive between 2.5 and 3.5 m year−1. (D) Basins that receive more than 3.5 m year−1. Error bars represent 2σ uncertainties. N is the number of basins in each rainfall bin.

  • Fig. 3 The effects of rainfall bin size and center on erosion coefficient calculations.

    Colored points show the resulting K values from regressions of binned sample data, where n = 2.2. These regressions are not influenced by m or Klp. The black line is derived from the stream-power model (Eq. 1c), where m = 1 and Klp = 2.2 × 10−9. An inverted histogram (calculated with 0.1 m year−1 bins) shows the distribution of mean annual rainfall (R) sample data analyzed in this study. Gray circles mark the four bins used in Fig. 2.

  • Fig. 4 Relationships between channel steepness and erosion, and their predictive power.

    (A) Red and blue curves are the stream-power model curves from the four mean annual rainfall (R) bins in Fig. 2. Black curve is the regression of all data. The gray dashed line is the stream-power model calculated with the median sample rainfall (2.1 m year−1). (B) Map of erosion rates based on the distribution of channel steepness (Fig. 1B), K = 3.2 × 109 m1 year−1 [calculated from the regression in (A) and Eq. 3a]. High-elevation, low-relief landscapes (HELR) are outlined in white. A white mask marks glacial landscapes above 4000 m above sea level. (C) Regressions of the four rainfall bins (red and blue curves) move toward the stream-power model (gray dashed) when ksn-q data are used. (D) Map of erosion rates based on the distribution of ksn-q and regional best-fit n and Klp values (see Materials and Methods). The 30-km-wide swath (magenta) shows the area sampled to calculate inset figure. Inset shows how the mean (black line) and SD (gray envelope) of erosion rates (E) near the foreland change with longitude.

Supplementary Materials

  • Supplementary Materials

    Climate controls on erosion in tectonically active landscapes

    B. A. Adams, K. X. Whipple, A. M. Forte, A. M. Heimsath, K. V. Hodges

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