%0 Conference Proceedings %T ASSESSING MODERN RATES OF RIVER SEDIMENT DISCHARGETO THE OCEAN USING SATELLITE GRAVIMETRY %+ Géosciences Rennes (GR) %A Mouyen, Maxime %A Longuevergne, Laurent %A Steer, Philippe %A Crave, Alain %A Robin, Cécile %< avec comité de lecture %( Source to Sink: a long term perspective of sediment budgets and sources characterization, Abstracts %B Source to Sink: a long term perspective of sediment budgets and sources characterization %C Rennes, France %P 79 %8 2016-11-30 %D 2016 %Z Sciences of the Universe [physics]/Earth SciencesConference papers %X The estimates of the worldwide sediment river discharge to the oceans suffer large uncertainties,mostly because sediment discharge measurements are scarce in space and time. Yet,knowing this sediment budget is critical in Earth and environmental Sciences, since it is underthe direct influence of surface processes (such as erosion, transport and sedimentation)and, in particular, controlled by climate, tectonics and human activities (dam, deforestation).Since 2002, the GRACE Satellite provides global gravity time series that have proven useful forquantifying mass transport, including continental water redistribution at the Earth surface (icesheets and glaciers melting, groundwater storage variations). Because, sediment accumulationin the oceanic sinks leads to a mass increase, we propose to use GRACE data to assess thesemass variations, and in turn the sediment discharge to the ocean. However, the order of magnitudeof mass variations due to sediments is only one tenth of the magnitude of continental water.As a result, unraveling the sedimentological contribution to GRACE signal is a challenge. Totackle it, we pair the analysis of regularized GRACE solutions at high spatial resolution correctedfrom all known contributions (hydrology, ocean, atmosphere) to a particle tracking modelthat predict the location of the sediment sinks for 13 rivers with the highest sediments loadsin the world. This particle tracking model combines global reanalysis of oceanic currents withavailable data on the grain size and the seasonality of the sediments load at the river mouthand is run over the same time range as GRACE data. We find encouraging correlation betweenGRACE spatial pattern of mass accumulation and the modeled pattern of sedimentation zonesfor some rivers, although some discrepancies between modeled and observed mass accumulationvalues are observed. The reasons for these misfits are a combination of inaccuracies bothin GRACE solutions and in the particle tracking model: 1) GRACE has a limited spatial resolutionand uncertainties, with residual contributions from off-target effects that are poorly estimated;2) The particle model is highly dependent on the oceanic currents’ velocity field, which alsosuffers from uncertainties and has limited spatial and temporal resolution as well; 3) We useliterature-based estimations of the seasonality of river sediment loads and associated grainsizes, both of which are notoriously uncertain data. We presently aim at refining our sedimentparticle tracking model in order to get better confidence in the spatial distribution of the sediments.This way, we expect to assess the annual riverine sediment discharge within the uncertaintyof GRACE, independently from uncertain in situ rivers’ sediment loads data. %G English %L insu-01406500 %U https://insu.hal.science/insu-01406500 %~ INSU %~ UNIV-RENNES1 %~ UR2-HB %~ CNRS %~ GR %~ OSUR %~ UR1-HAL %~ UR1-SDLM %~ GR-PPDB %~ GR-DIMENV %~ UNIV-RENNES2 %~ TEST-UNIV-RENNES %~ TEST-UR-CSS %~ UNIV-RENNES %~ INRAE %~ UR1-ENV %~ GR-ET %~ GR-R %~ GR-DEMO %~ RESEAU-TELEDETECTION-INRAE