Physical features of Adam’s Bridge interpreted from ICESat-2 based high-resolution digital bathymetric elevation model

Abstract

Abstract Adam’s Bridge is a submerged ridge connecting India and Sri Lanka, generally regarded as a chain of shoals extending for ~ 29 km from Dhanushkodi on the Indian side to Talaimannar Island of Sri Lanka. A high-resolution digital bathymetric elevation model generated using the seafloor returned photons of ICESat-2 was used to understand the intricate details of Adam’s Bridge structure. Photons emanating from ICESat-2’s green laser have the potential to detect the seafloor up to a depth of ~ 40 m; taking a cue from this potentiality, in our research, we have accrued ~ 0.2 million photons representing the depth information and generated a 10 m resolution bathymetric data for the extent of Adam’s Bridge. Visual interpretations made from this bathymetric data through 3D perspectives with multi-directional lighting effects, and also with the derived parameters like contours, slope, and volumetric analysis, enabled us to recognize the current form of Adam’s Bridge’s physical features. The results from our research confirm that, in its entirety, Adam’s Bridge is a submarine continuation of Dhanushkodi and Talaimannar Island. Throughout the crest line of Adam’s Bridge, approximately 1.5 km on either side is highly undulating within the super-shallow water with occurrences of sudden depths. There is an asymmetry of transverse slopes to the base on both sides of Adam’s Bridge, indicating dominant transgression of material energy from the waters of the Gulf of Mannar compared to the Palk Strait. The volume of Adam’s Bridge computed in our research yielded a value of ~ 1 km3; interestingly, only 0.02 percent of this volume is above the mean sea level, and in general, the same is visible in optical satellite imagery—in total ~ 99.98 percent of the Adam’s Bridge is submerged in shallow and super-shallow waters.