Present‐day subsidence in the Ganges‐Brahmaputra‐Meghna Delta: eastern amplification of the Holocene sediment loading contribution

The subsidence of the Ganges-Brahmaputra-Meghna Delta (GBMD) drastically increases the adverse impacts of coastal flooding and exacerbates the vulnerability of populations from ongoing rapid sea level rise. We focus here on estimating the present-day subsidence rates induced by the loading of sediments continuously deposited within the GBMD over the past 11,000 years. By constructing a realistic GBMD 3-D numerical model with laterally variable mantle and lithospheric structure, we demonstrate for the first time that the presence of the strong Indian Craton and the weakened Indo-Burma margin results in significant amplification of subsidence driven by sediment loading in the eastern part of the delta, where the population density is the highest (>1,000 habitants per km 2). Although uncertainties remain regarding the amplitude of subsidence, the rate estimates (2-3 mm/year) are found to be comparable to the present-day global mean sea level rise.