Recording the underwater calls of marine mammals is one of the most promising methods to study distribution and seasonal migration of these animals in the ice-covered Antarctic. Visual sightings of marine mammals in Antarctic waters are rare since human access is limited and animals only occasionally surface to breathe. Acoustic recordings, on the other hand, can be made year round. By means of the PALAOA observatory, ocean acoustics experts from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have discovered that leopard and Ross seals populate Antarctic waters near Neumayer Station III.
For many sounds it is now known by what species they are produced and, in some cases, in what type of behavioural context they are produced. Such acoustic data can be used to derive information on the timing of mating and reproduction of the various species. Acoustic behaviour of leopard and Ross seals, for instance, shows that both species also reproduce in coastal Antarctic waters. Previously this was only known for Weddell and crabeater seals.
Inter-annual comparisons of acoustic data indicate that the timing of reproduction is linked to the availability of certain types of ice on which the animals give birth to their young. “Some seal species actually are acoustically present in the PALAOA recordings in the same calendar week every year,” Dr. Ilse van Opzeeland describes the surprisingly exact timing of the animals. Researchers at the Alfred Wegener Institute were astonished to hear humpback whales on the edge of the Antarctic continent, even in austral winter. The observatory has also recorded calls of Antarctic blue whales, thereby refuting the existing presumption that the largest animals living on Earth avoid ice-covered waters.
Even 50 years after the end of commercial whaling in Antarctica very little is known about the long-term population development of these nearly exterminated giant whales. Traditional counts based on sightings often record only a few of these marine mammals during an expedition over several months. The PALAOA data, on the other hand, contain blue whale vocalisation almost every day because the calls of these animals have a very great range extending to several hundred kilometres. Such information is extremely important to gain a general understanding of the behaviour, size and recovery of the stocks of large whales, which are still endangered in a variety of ways.
The loudest sounds recorded by PALAOA stem from iceberg collisions. About once a year giants the size of Berlin bump into each other or into the edge of the ice shelf. These create quite a racket in the Bremerhaven offices of the ocean acoustics specialists, whose daily work is accompanied by the live sounds from the Antarctic. Aside from their usefulness for research, the extraordinary sounds from the Antarctic Ocean have also found their way into radio and television as well as into the works of musicians, composers and creative artists. In 2010 more than three million visitors saw and heard the walk-on sculpture and sound installation “Iceberg PALAOA” floating on the Ruhr River in Essen – it represented one of the highlights of the European Capital of Culture “RUHR2010”.
Background:
PALAOA stands for PerenniAL Acoustic Observatory in the Antarctic Ocean and also means “whale“ in the ancient Hawaiian language. It is the only hydroacoustic observatory in the immediate vicinity of the Antarctic continent, or more exactly on the Ekström Ice Shelf in the eastern Weddell Sea at 70°31’S 8°13’W. In December 2005, several hydrophones and sensors were positioned under the ice through holes drilled through the floating, 100 meter thick ice shelf around 25 kilometres north of the German Neumayer Station. Continuous recording of the underwater sounds for a period of several years enables unique acoustic observation of the underwater animal world. The recordings are made year-round and enable comparisons of the acoustic environment between years. In terms of energy, PALAOA is self-sufficient: solar cells and a wind generator supply the observatory with renewable energy 90% of the time. During the months of darkness in the Antarctic winter and at temperatures down to 50°C, a fuel cell driven with methanol springs into action on windless days to guarantee continuous operation. The acoustic observatory has recorded more than 30,000 hours (6 terabytes) of data in the past five years and registers a broad range of frequencies. This means PALAOA detects the low-frequency sounds of blue whales as well as the high-frequency clicks produced by orcas, that function as a biological echo sounder for orientation. Alongside acoustic data, oceanographic data, the movement of the ice shelf and sea ice and local shipping traffic are recorded in order to study their influence on the behaviour of the large marine mammals. Researchers hope to collect data for several more years until the ice shelf on which PALAOA is located breaks off and moves around the southern continent as a drifting iceberg.
The Alfred Wegener Institute
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the sixteen research centres of the Helmholtz Association, the largest scientific organisation in Germany.
You will find examples of sounds and valuable information on PALAOA on the Internet at: http://www.awi.de/de/aktuelles_und_presse/hintergrund/palaoa_wie_klingt_das_suedpolarmeer/
The recordings are transmitted via a WLAN and satellite link directly to Bremerhaven and can be heard as a livestream here: http://www.awi.de/PALAOA
Contact
Dr Ilse van Opzeeland
Alfred Wegener Institute
Phone: +49 (0)471 - 4831 - 1169
Email: Ilse.van.Opzeeland(at)awi.de
Folke Mehrtens
Department of Communications und Media Relations
Phone: (0)471 - 4831 - 2007
Email: Folke.Mehrtens(at)awi.de
