Listening to the sound of ice

Delft researchers followed the trajectories of two drifting icebergs through the Indian Ocean by listening to the underwater sounds of cracking and colliding ice.

While studying the sounds a large network of hydro-acoustic stations has been registering in the Indian Ocean for the last twelve years, Dr. Läslo Evers (CEG and KNMI), Dr. Mirjam Snellen (of the acoustic remote sensing group, AE Faculty), and two colleagues from England and Australia, discovered sounds which had to originate from large moving objects. Cross-referencing with satellite images confirmed that they were listening to icebergs cracking and disintegrating as they headed northeast towards more temperate waters.

The researchers followed two of these icebergs, which, at the start of their journey at Antarctica had diameters of tens of kilometres. One (dubbed C20) headed up north in 2005 and 2006. The other drifted off Antarctica in 2009 (code name B17B). They were able to follow their thousands of kilometres long trajectories with much more accuracy than satellites could. What’s more, they identified trails of small icebergs that calved from the main berg, which were too small to be picked up by satellite monitoring but which were still big enough to pose serious threats to ships. The findings were published this autumn in Geophysical Research Letters.

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