Mud sound speed profile constraints from sub-bottom arrival times

Arrival times of sub-bottom reflected paths together with co-located direct measurements of the angle of intromission provide narrow constraints on the sediment sound speed profile. Measurements of these two quantities at the central New England Mud Patch in March 2017 indicate that the average sound speed gradient in the upper ∼3 m and upper ∼9 m of mud is ∼6 s-1. Gradients of 5 s-1 and 7 s-1 over the upper ∼9 m are too small and large, respectively. Below ∼9 m, the sand-mud transition interval has a gradient of ∼200 s-1.