Assessing modern river sediment discharge to the ocean using satellite gravimetry

Abstract

Recent acceleration of sand extraction for anthropic use threatens the sustainability of this major resource. However, continental erosion and river transport, which produce sand and sediment in general, lack quantification at the global scale. Here, we develop a new geodetic method to infer the sediment discharge to ocean of the world’s largest rivers. It combines the spatial distribution of modern sedimentation zones with new high-resolution (~170 km) data from the Gravity Recovery and Climate Experiment (GRACE) mission launched in 2002. We obtain sediment discharges consistent with in situ measurements for the Amazon, Ganges-Brahmaputra, Changjiang, Indus, and Magdalena rivers. This new approach enables to quantitatively monitor the contemporary erosion of continental basins drained by rivers with large sediment discharges and paves the way toward a better understanding of how natural and anthropic changes influence landscape dynamics.

Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region

“…This vast amount of precipitation feeds the Amazon river, ranked as the world's largest river in terms of annual discharge 2 . The Amazon river discharge contributes~17% of global river freshwater input to the ocean 2 , significantly affecting the physical and biogeochemical upper ocean properties in the coastal and neighboring oceans [3][4][5][6][7] . One prominent feature is the so-called Amazon plume region (APR), which is characterized by relatively low ocean salinity 3,4,8 and high nutrients brought by the Amazon river discharge 3,4,9,10 .…”

Quantifying sediment mass redistribution from joint time-lapse gravimetry and photogrammetry surveys

“…It has been widely applied in the fields of glaciology, hydrology and solid earth processes, either from space, with the Gravity Recovery and Climate Experiment (GRACE) mission (Farinotti et al, 2015;Han et al, 2006;Longuevergne et al, 2013;Pail et al, 2015;Tapley et al, 2004), or from terrestrial instruments (Van Camp et al, 2017;Crossley et al, 2013). Recent studies demonstrate the new potential of time-lapse gravity for studying surface processes as well, because the mass of deposited or eroded sediment can also significantly alter the gravity field Mouyen et al, 2013Mouyen et al, , 2018.…”

The importance of sediment in sea-level change

“…Deposition rates are traditionally inferred from the age and thickness of sediment cores, which typically yield rates over ~10 2 -10 5 years. Recently, new approaches have been developed to infer sediment deposition rates through remotely sensed perturbations in the gravity field (Mouyen et al 2018). Although no single method can yield a continuous record of the history of erosion and deposition, the combination of methods provides useful constraints on the history of sediment redistribution over a range of timescales.…”