Sea-level responses to erosion and deposition of sediment in the Indus River basin and the Arabian Sea

- We model sea level responses to large-scale sediment erosion and deposition.
- We focus on the area around the Indus River basin and northeastern Arabian Sea.
- Fluvial sediment fluxes drive regional sea level changes over >1000-yr timescales.
- This suggests modern sea level is still responding to past erosion and deposition.

Changes in sea level are of wide interest because they shape the sedimentary geologic record, modulate flood-related hazards, and reflect Earth's climate. One driver of sea-level change is the erosion and deposition of sediment, which induces changes in sea level by perturbing Earth's crust, gravity field, and rotation axis. Here we use a gravitationally self-consistent global model to explore how sediment erosion and deposition affected sea level during the most recent glacial-interglacial cycle in the northeastern Arabian Sea and the Indus River basin, where fluvial sediment fluxes are among the highest on Earth. We drive the model with a widely used reconstruction of ice mass variations over the last glacial cycle and a sediment loading history that we constructed from published erosion and deposition rate measurements. Our modeling suggests that sediment fluxes from the Indus River are large enough to produce meter-scale changes in sea level near the Indus delta in as little as a few thousand years. These sea-level perturbations are largest closest to the center of the Indus delta, and they grow larger over time as sediment deposition increases. This implies that the elevation of sea-level markers near the Indus delta will be significantly altered by sediment transfer over millennial timescales, and that such deformation should be accounted for in studies that use paleo-sea-level markers to infer past ice sheet volume or explore local processes such as sediment compaction. Our analysis highlights the role that massive fluvial sediment fluxes play in driving sea-level changes over >1000-yr timescales from the Indus River, and, by implication, from other rivers with large sediment fluxes.