The PALAOA Base
Even before the PALAOA station was set up, scientists made underwater recordings. Hydrophones, i.e. underwater microphones, are either attached to buoys for this purpose or anchored directly on the sea floor. In the Antarctic Ocean, however, buoys are frequently destroyed by drifting ice floes. Large icebergs that plough through the bottom pose a risk for anchoring devices in shallow coastal water. The best solution, in fact, is to fix the hydrophones directly in the ice.
The Observatory
The massive Ekström Ice Shelf where PALAOA was set up can reach a thickness of one hundred metres thick and offers optimal protection for the equipment. Thus, four holes were drilled in the ice 15 km north of Neumayer Station, west of Akta Bay, in order to lower the hydrophones into the water body underneath. This location is well suited because the ice shelf here stretches into the sea like the fingers of an extended hand. The finger on which PALAOA is situated, the North Pier, is surrounded by water and thus guarantees exceptionally good recordings of the ocean.
A hot-water drill developed by AWI was used to drill the holes in the thick ice mass. It took twelve hours to drill a hole and the drill consumed over 750 kW to melt the ice.
PALAOA has an autonomous power supply. The station obtains power from solar panels, wind generators and a fuel cell. The energy is used, among other things, to send the data collected via wireless LAN to Neumayer Station. From there they are transmitted to the Alfred Wegener Institute in Bremerhaven. PALAOA generates huge volumes of data, around 150 GB a day. To facilitate the scientists’ work, a preselection is made by the computer. It is additionally possible to visualise the sounds heard as spectrograms on a PC.
Research
Scientists plan to record underwater sounds with PALAOA for several years. Through the long-term recordings they hope to clarify various questions relating to oceanic acoustics:
- How do the species-specific calls sound and how many different types of vocalisation do the individual species have in their repertoire?
- How many animals are there in the measurement area and how can they be distinguished?
- How can we calculate the movements of the marine mammals with the help of acoustic data?
- What impacts do anthropogenic sounds, i.e. those produced by people, have on the behaviour of the animals?
The data that PALAOA collects are for the most part free of anthropogenic sounds since they are recorded in an environment that is still extensively untouched by humanity. These pure data can also be used to develop a technology making it possible to filter out acoustic recordings - for instance, the sounds caused by a ship propeller. Research vessels that also collect sound samples could work with the technology to obtain better results.