Sea level response to rapid sediment redistribution in Taiwan

Abstract:

The contribution of sediment deposition to sea-level change has recently begun to receive significant attention, and these studies have shown that sediment deposition is capable of perturbing sea level by several meters over millennial timescales by altering crustal elevation and the local gravitational field. However, the complementary role of erosion has received less attention, in part because many rapidly eroding areas are located in mountain ranges far from the coast where erosion's effects on sea level are less apparent. Taiwan is ideal for studying the influence of erosion on sea level because it experiences rapid erosion within tens of km of its coastline, coupled with rapid deposition offshore. Here we develop a sediment loading history for Taiwan since the last interglacial (~120 Ka) through a compilation of erosion rates and deposition rates supplemented with a deposition and compaction model for areas and times where deposition constraints are lacking. We then use the resulting sediment redistribution history to drive a global gravitationally self-consistent sea level model. Our simulations show that that there is a rapid sea level fall as erosional unloading outpaces depositional loading along Taiwan's eastern margin. This signal (rapid sea level fall) differs in sign from areas influenced primarily by rapid deposition (e.g., deltas), and suggests that sediment redistribution could drive >100 m of SL change on Taiwan's east coast since 120 Ka. This can account for some of the observed discrepancy between modeled sea level histories and paleo-sea-level markers, and highlights the importance of accounting for both unloading and deposition in paleo-sea-level reconstructions for tectonically active areas.