Combining GRACE and satellite altimetry data to detect change in sediment load to the Bohai Sea

The Gravity Recovery and Climate Experiment (GRACE) satellites provide a powerful tool for monitoring sedi-ment mass change. However, signal leakage from nearby groundwater storage depletion in the North China Plain limits the potential capacity of GRACE to estimate sediment input from the Yellow River flows into the Bohai Sea. In the present work, we developed an improved approach based on forward modeling to reduce signal leakage from GRACE data and combined it with satellite altimetry to recover sediment load changes from 2003 to 2013 to the Bohai Sea. The total sediment input averaged 1.7 +/- 0.8 Gt/yr, which agrees well with the estimate based on in-situ sediment data measured from the sediment cores (1.1 Gt/yr). Our method is also capable to de-scribe sediment seasonal variations, with higher inputs in winter and spring, which confirm the output simulated by the sediment transportation model. We make presently tentative connections of seasonal variations to sedi-ment resuspension driven by climatic monsoons contributed rough seas: although sediment load in rivers peaks in summer, low water discharge of the Yellow River leads to most of the sediment being deposited in a nar-row area near the river mouth and not transported into the Bohai Sea; in winter and spring, huge waves provide favorable conditions for resuspension resulting in large amounts of sediment near the estuary being transported to the ocean along with northward waves. Moreover, our results indicate coastal erosion is also a nonnegligible resource of the sediment in the Bohai Sea. Comparing to the traditional approach, our study provides a new tech-nological way to derive sediment in the Bohai Sea, which is capable of providing continuous measurements with improved timeliness at a lower cost.(c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study developed an improved method to estimate sediment input changes in the Bohai Sea using GRACE data and satellite altimetry. The results revealed seasonal variations in sediment input and the contribution of coastal erosion.