Contributions of a Strengthened Early Holocene Monsoon and Sediment Loading to Present-Day Subsidence of the Ganges-Brahmaputra Delta

Mikhail Karpytchev (1) , V. Ballu (1) , Y. Krien (1) , Melanie Becker (1) , S. Goodbred (2) , G. Spada (3) , S. Calmant (4) , C. K Shum (5, 6) , Z. Khan (7)

1 LIENSs - LIttoral ENvironnement et Sociétés
2 Vanderbilt University [Nashville]
3 DiSPea - Dipartimento di Scienze Pure e Applicate
4 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
5 School of Earth Sciences
6 Institute of Geodesy & Geophysics
7 Institute of Water Modelling

The contribution of subsidence to relative sea level rise in the Ganges‐Brahmaputra delta (GBD) is largely unknown and may considerably enhance exposure of the Bengal Basin populations to sea level rise and storm surges. This paper focuses on estimating the present‐day subsidence induced by Holocene sediment in the Bengal Basin and by oceanic loading due to eustatic sea level rise over the past 18 kyr. Using a viscoelastic Earth model and sediment deposition history based on in situ measurements, results suggest that massive sediment influx initiated in the early Holocene under a strengthened South Asian monsoon may have contributed significantly to the present‐day subsidence of the GBD. We estimate that the Holocene loading generates up to 1.6 mm/yr of the present‐day subsidence along the GBD coast, depending on the rheological model of the Earth. This rate is close to the twentieth century global mean sea level rise (1.1–1.7 mm/yr). Thus, past climate change, by way of enhanced sedimentation, is impacting vulnerability of the GBD populations.

Domaines: Milieux et Changements globaux; Géomorphologie

Mikhail Karpytchev, V. Ballu, Y. Krien, Melanie Becker, S. Goodbred, et al.. Contributions of a Strengthened Early Holocene Monsoon and Sediment Loading to Present-Day Subsidence of the Ganges-Brahmaputra Delta. Geophysical Research Letters, 2018, 45 (3), pp.1433-1442. ⟨10.1002/2017GL076388⟩. ⟨hal-01738232⟩