Global dominance of tectonics over climate in shaping river longitudinal profiles

Hansjörg Seybold,Jeff P Prancevic,Wouter R Berghuijs,James W Kirchner

doi:10.1038/s41561-021-00720-5

Abstract

River networks are striking features engraved into Earths surface, shaped by uplift and erosion under the joint influence of climate and tectonics. How a river descends along its course – its longitudinal profile – varies greatly from one basin to the next, reflecting the interplay between uplift and erosional processes. It has recently been argued that climatic aridity should be a first-order control on river profile concavity, but the importance of climate relative to other factors has not been tested at global scale. Here we show, using recent global datasets of river profiles and tectonic activity, that tectonics is much more strongly expressed than climate in global patterns in river profile concavity. River profiles tend to be more strongly concave in tectonically active regions along plate boundaries, reflecting tectonically induced spatial variations in uplift rates. Rank correlations between river profile concavity and global tectonic proxies (basin slope and two indices of seismic risk) are much stronger than those between river concavity and precipitation, potential evapotranspiration, or aridity. These results show that tectonics, and not climate, exerts first-order control on the shape of river longitudinal profiles globally.

Highlights

Rivers dynamically shape Earth’s landscapes [Twidale, 2004; Willet et al, 2014], ecosystems [Palmer et al, 2009], and human society [Mård et al, 2018]
River longitudinal profiles are shaped by the interplay between tectonic forces, which drive spatial patterns of uplift and subsidence, and the processes of fluvial erosion and deposition, which modify the topographic relief created by tectonics [Gilbert, 1877; Sklar & Dietrich 1998; Whittaker et al, 2008; Ferrier et al, 2013; Kirby & Whipple, 2012; Yang et al, 2015]
By testing how river profile concavity correlates with both climatic and tectonic indices, we reveal a clear dominance of tectonics over climate in shaping river longitudinal profiles globally

Summary

Introduction

Rivers dynamically shape Earth’s landscapes [Twidale, 2004; Willet et al, 2014], ecosystems [Palmer et al, 2009], and human society [Mård et al, 2018]. Because headwaters have smaller streamflows, they must be steep for incision to keep pace with uplift, but further downstream, larger streamflows can accomplish the same incision at a gentler river gradient In steady state, this relationship between erosivity and streamflow results in the characteristic concave-up shape of river longitudinal profiles [Gilbert, 1877; Whipple & Tucker, 1999; Chen et al, 2019]. NCI values vary regionally (Fig. 1), indicating a tendency toward more concave river profiles in the Rocky Mountains, Andes, Himalaya, and Tibetan Plateau, along the Pacific Ring of Fire and the East African rift valley, and in mountains stretching from the Alps to the Zagros mountains of Iran. These include the subduction zones, transform faults, and rifts of the Pacific Ring of Fire and their associated mountain ranges; the convergent boundary between the Eurasian plate and the African, Arabian and Indian plates, which is responsible for the uplift of the Alpine-Himalayan orogenic belt and the Tibetan plateau; the East African Rift; the rifts and transform faults bounding the Yangtze, Amur and Okhotsk plates; the convergent boundaries between the South American plate and the Altiplano and North Andes plates; and the transform faults bounding the Caribbean plate

Discussion

Methods