Remote hydroacoustic sensing of large icebergs in the southern Indian Ocean: Implications for iceberg monitoring

Hydro-acoustic signals generated by drifting icebergs that crack, disintegrate and collide were identified on two hydrophone arrays in the Indian Ocean. These hydrophone arrays are deployed in the SOund Fixing And Ranging (SOFAR) channel, enabling the detection of small sources over ranges of several thousand kilometers due to the low attenuation. Source locations estimated from the signal bearings at the arrays are used to monitor two very large icebergs, C20 and B17B. Spatial and temporal correlation of the location estimates with satellite observations confirm that the icebergs can be hydro-acoustically resolved. Hydro-acoustic generation rates at both C20 and B17B are highest at times of observed break-up. For C20, which underwent continuous break-up, clusters of events to the south-east of the main iceberg show that hydro-acoustic observations can identify trails of icebergs that calved from the main berg whose dimensions are less than that easily resolved by moderate resolution satellite monitoring.