Long-term effects of ocean temperature rise on the deep sea #

Gianluca Audone, Matthew Nunes, Philippe Blondel, Chris Budd, Peter Harris, Stephen Robinson

12:30 Monday in 4Q05.

Part of the Acoustics session.

Abstract #

In this talk I will show how underwater acoustics and lower frequency analysis can help understand the impact of climate change in the deeper sea.

The Comprehensive Nuclear Test Ban Treaty Organization operates a global International Monitoring System, with 11 hydroacoustic stations around the globe located in the deep-sea sound channel. Continuous measurements from this now available for civilian use provide 20 years of data at frequencies of up to 100 Hz over many years. The relatively long time scale for this data allows us to use it to investigate climate change phenomena. In particular we can find a link between sound pressure levels at 1km depth and the surface temperature of the ocean. The latter is a key factor to better understand the Earth’s climate system. The Intergovernmental Panel on Climate Change concluded in 2014 that the increase in temperature has mostly affected the upper (0 – 700 m) ocean while assessing the impact of climate change in the deep sea (> 1000 m) is a challenging task due to the difficulty to gathering long-term comprehensive data.

In this talk I will look at sound pressure datataken from Wake Island, station H11, in the north Pacific and also Cape Leeuwin, station H01, located the Indian Ocean. I will consider multiscale aggregations of 1-minute power spectral density (PSD) levels and sound energy measure over several days and will show a correlation of them with sea surface temperature (SST) measurements. In particular we can detect seasonal changes in the SST as well as longer term climatic variations. The spectral analysis also shows periodic features in PSD levels around 15 to 31 Hz.