12.5 kHz raw echosounder data collected on the Antarctic Circumnavigation Expedition during the austral summer of 2016/2017

These data consist of raw echosounder observations collected during ACE (Leg1-Leg3) using an EK80 WBT operating at 12.5 kHz. The instrument was calibrated at South Georgia during the expedition (Leg 3) and corrections were applied prior to calculation of the volume backscattering strength (Sv). The signal-to-noise ratio (SNR) was analysed and was deemed very poor at depths greater than 1000 m. Therefore, only data collected between the transducer depth (8.4 m) and 1000 m were archived. Sv values within this depth range that had poor SNRs (<2) were deemed to be bad data and set to a value of NA. Observations were made using a pulse duration of 16.384 ms (c. 24 m) and are therefore not suitable for fine-scale studies (e.g. analysis of krill swarms). They are more suited to studies relating to large-scale biological features such as deep scattering layers.