Episodic deep-water currents observed in NESMA and their implication on acoustics near the New England Seamounts

Naval Postgraduate School deployed a network of Moored Autonomous Noise Recorders (MANRs) in the vicinity of the Atlantis II Seamounts for 2 months during the 2023 New England Seamounts Acoustics (NESMA) pilot experiment and for 5 months during the 2024 NESMA field experiment. In each experiment, two MANRs were placed on the steep flanks of the Atlantis II Seamounts and two were placed along a deep trench. Strong, episodic near-bottom flows were observed a few meters above the seafloor during both experiments at water depths between 2550 and 4450 m. An assemblage of measurements from tilt current meters, flow noise over the MANR hydrophones and variations in in situ temperature were used to identify the unexpected flows. In this work, we examine the characteristics of the irregular flows, their spatial and temporal relationship with the Gulf Stream, and the implications of the flows for sound propagation and acoustic measurements in this region of complex bathymetry and oceanography. [Work supported by ONR.]