Bifurcate responses of tidal range to sea-level rise in estuaries with marsh evolution

Abstract

The response of tidal range in tidal marshes under sea-level rise (SLR) is essential to the marsh resilience, but how tidal ranges respond to different marsh evolutions remains unclear. Here, we show the existence of bifurcate responses of tidal range to SLR using both numerical model and theoretical analyses. The tidal range tends to increase if marsh accretion keeps pace with SLR; otherwise, the tidal range tends to decrease. As tidal range plays the key role in marsh evolution, the interactions between changing tidal range and marsh evolution lead to positive feedback on marsh resilience. If the marsh accretion can keep up with the SLR, the increase in the tidal range can enhance marsh resilience to SLR. If the marsh cannot keep up, the decrease in the tidal range may further threaten the marsh resilience or even lead to marsh retreat.