ABSTRACT
Over a 4-year period between 2015 and 2019, in-situ time series measurements of ocean ambient noise over the frequency range 100 Hz to 10 kHz, by an autonomous passive acoustic monitoring system have been made in the Kongsfjorden, Svalbard, Arctic. We characterize the noise due to sea ice melting during winter (December-January). This unique observation reveals loud noise signatures, of the order of 8 dB higher than the background noise, showing the signature of sea ice melting. Such observations are crucial for monitoring sea ice melting, especially during winter, to understand the recent warming of Arctic waters. The anomalous air temperature due to local atmospheric forcing and warming of ocean temperature in the fjord through ocean tunneling, individually or combinedly, is responsible for such sea ice melting. The cyclonic events in the Arctic are responsible for the anomalous atmospheric and ocean conditions, causing sea ice melting in winter.
ABSTRACT
The primary objective of this work was to present the acoustical identification of humpback whales, detected by using an autonomous ambient noise measurement system, deployed in the shallow waters of the Southeastern Arabian Sea (SEAS) during the period January to May 2011. Seven types of sounds were detected. These were characteristically upsweeps and downsweeps along with harmonics. Sounds produced repeatedly in a specific pattern were referred to as phrases (PQRS and ABC). Repeated phrases in a particular pattern were referred to as themes, and from the spectrographic analysis, two themes (I and II) were identified. The variation in the acoustic characteristics such as fundamental frequency, range, duration of the sound unit, and the structure of the phrases and themes are discussed. Sound units were recorded from mid-January to mid-March, with a peak in February, when the mean SST is approx. 28 degree C, and no presence was recorded after mid-March. The temporal and thematic structures strongly determine the functions of the humpback whale song form. Given the use of song in the SEAS, this area is possibly used as an active breeding habitat by humpback whales during the winter season.
