Chinese scientists describe inertial chimneys in the ocean — South China Morning Post

Chinese researchers have studied how wind energy from the ocean surface can be transmitted thousands of metres into the water and reach the seafloor. In the Kuroshio Extension region east of Japan, they recorded concentrated flows of this energy, which they called “inertial chimneys,” the South China Morning Post reports.

The study was conducted by specialists from the Institute of Oceanology of the Chinese Academy of Sciences. The results were published in October in the peer-reviewed journal Deep Sea Research Part I: Oceanographic Research Papers. The authors analysed two years of data from 46 seafloor stations deployed across a 600-by-600-kilometre area in the Kuroshio Extension region.

Data from a US observation system

The instruments were installed on the seafloor in 2004–2006 as part of the Kuroshio Extension System Study, funded by the US National Science Foundation. The system recorded the travel time of an acoustic signal from the bottom to the surface and back, pressure near the bottom, and near-bottom currents.

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The researchers focused on near-inertial internal waves — large oscillations of water masses that occur when wind moves the ocean’s upper layers and Earth’s rotation affects that movement. Such waves can carry energy through the stratified water column, where warm surface layers and cold deep layers usually limit water exchange.

The role of ocean eddies

According to the team’s findings, when the waves pass through anticyclonic eddies, their energy is directed downward and concentrated in the shape of a funnel. The scientists called this process the formation of an inertial chimney.

The authors estimated that 68% of the energy of near-inertial waves near the bottom comes from the ocean’s upper layers, while another 32% is generated by local near-bottom currents. In their view, long-term observations of temperature, salinity and sound speed in water may be useful for forecasting the marine environment, deep-sea engineering, and assessing conditions for underwater detection and communication.