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Institute of Marine Research

Acoustic data from Nansen Legacy Cruise - Arctic Basin Joint Cruise 2-2

Recommended citation:
Randi B. Ingvaldsen, Elena Eriksen, Harald Gjøsæter, Arill Engås, Birte Katarina Schuppe, Karen M. Assmann, Heather Cannaby, Padmini Dalpadado, Bodil A. Bluhm (2022) Acoustic data from Nansen Legacy Cruise - Arctic Basin Joint Cruise 2-2 https://doi.org/10.21335/NMDC-1275935147
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Abstract
Scrutinized acoustic data from the Nansen Legacy Cruise - Arctic Basin Joint Cruise 2-2 in the Eurasian Basin during August-September 2021. The acoustical data were obtained from a Simrad EK80 echosounder mounted behind an ice window under the hull at R/V Kronprins Haakon. The echosounder was calibrated according to standard procedures on 19.01.2021. The 38 KHz frequency was used to determine backscatter intensity. The backscattering data output were in the form of sA, where sA is the Nautical area scattering coefficient (NASC). Only data from periods when the ship was stationary were used due to mechanical noise when the vessel was moving through sea ice. An hour of acoustic data was selected from as near the trawl locations as possible. The data were integrated over the time period and stored at a grid of 10 m depth and 1 hour (3600 seconds). sA was classified into five classes according to their sV by sequential thresholding at 38 KHz. The five categories used were S70, S75, S80, S85 and S90, where S70 represent the organisms with strongest target strength (TS) and/or the highest density, while S90 represent the organism with weakest TS and/or the lowest density. TS measurements of scatterers were identified using detector type SED (Single echo detector), Min TS -70 dB, Pulse length determination Level: 6 dB, Minimum echo length: 0.5 (relative to pulse length), Maximum echo length 2.0 (relative to pulse length), Max gain compensation 6 dB, Phase Deviation Check: On. Max phase deviation: 8 steps. To avoid TS distributions being biased towards higher values due to reduced signal-to-noise ratio in the outer parts of the beam, we restricted the TS data to be within 2 o off axis for further application. TS measurements were extracted from the frequencies 18 and 38 KHz.
Scientific keywords:
EARTH SCIENCE> OCEANS> OCEAN ACOUSTICS
Key words:
Acoustic data, EK80, echosounder
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