Out-of-plane arrivals recorded by surface drifters during the Northern Ocean Rapid Surface Evolution experiment

The Northern Ocean Rapid Surface Evolution (NORSE) focuses on characterizing the key physical processes that govern the predictability of upper-ocean rapid evolution events. The principal experimental site is Jan Mayen Channel, which connects the Greenland and Norwegian Seas. During the fall 2022 process cruise, signals from a moored source transmitting a 135-second-long LFM upsweep in the 500–1500 Hz band every four hours were recorded by three SVP Drifters equipped with hydrophone arrays. Over a three-day period, the drifters moved north across Jan Mayen Channel toward the moored source. The individual recordings are subject to variable levels of ambient sound caused by changing wind conditions and platform noise. In recordings with positive SNR, an in-plane arrival is observed. In a subset of these recordings, a second arrival is observed having travel time consistent with a propagation path from the moored source, reflecting off the ridge on the south side of the channel, and arriving at the drifters. A third arrival is also observed having travel time consistent with reflection from face of the bathymetric rise on the east end of the channel which forms Jan Mayen Island. This talk will present the measurements and explain the data though forward modeling. [Work supported by ONR.]