Project Participants

Nikolay Zabotin (PI)
Oleg A. Godin (Co-PI)

Motivation

Recently, observations were reported of rather unusual atmospheric wave activity in Antarctica [Chen et al., 2016]. With a lidar instrument operating at McMurdo, Antarctica, Chen et al. [2016] observed persistent, large-amplitude gravity waves with 3–10 h periods and vertical wavelengths between 20 and 30 km from the stratosphere to lower thermosphere. Remarkably, these waves were present during every lidar observation throughout the five-year observation period [Chen et al., 2016]. No similar atmospheric wave activity was ever observed at mid- and low-latitude locations.

We hypothesize that the persistent atmospheric waves in mesosphere and lower thermosphere, which are observed at McMurdo, Antarctica, are related to the ice cover and, specifically, to low-frequency vibration resonances of the Ross Ice Shelf. Our preliminary analysis indicates that the temporal and spatial scales of atmospheric waves, which would be radiated by the lowest-order modes of RIS vibrations, are consistent with the lidar observations of Chen et al. [2016].

In this project we studied the physics of the resonance vibrations of the Ross Ice Shelf and the atmosphere, the mechanisms of their excitation, and interconnections between them. We analyzed the role of the Ross Ice Shelf as a source of waves in the atmosphere and in the ocean.
 

Chen, C., X. Chu, J. Zhao, B. R. Roberts, Z. Yu, W. Fong, X. Lu, and J. A. Smith (2016), Lidar observations of persistent gravity waves with periods of 3–10 h in the Antarctic middle and upper atmosphere at McMurdo (77.83°S, 166.67°E), J. Geophys. Res. Space Phys., 121, doi: 10.1002/2015JA022127. link
 

Publications

Godin, O. A., and N. Zabotin (2016), Resonance vibrations of the Ross Ice Shelf and observations of persistent atmospheric waves, J. Geophys. Res. Space Physics, 121, 10,157–10,171, doi:10.1002/2016JA023226. link

Godin, O. A., Zabotin, N. and Zabotina, L. (2020), Atmospheric resonances and their coupling to vibrations of the ground and waves in the ocean, Earth Planets Space, 72, 125, doi: 10.1186/s40623-020-01260-9. link

Zabotin, N., Godin, O. A., Bromirski, P. D., Jee, G., Lee, W. S., Yun, S., and Zabotina, L. (2023), Low-Frequency Wave Activity in the Ocean - Ross Ice Shelf - Atmosphere System, Earth and Space Science, 10, e2022EA002621, doi: 10.1029/2022EA002621. link

Godin, O. A., Zabotin, N. and Zabotina, L. (2023), Atmospheric wave radiation by vibrations of an ice shelf, Journal of Geophysical Research: Atmospheres, 128, e2023JD039121, doi: 10.1029/2023JD039121. link

Results

We explored how low-frequency (with periods of the order of few hours) waves interact in the Ross Ice Shelf (RIS), the Ross Sea, and the atmosphere above them. By using a unique set of tools like hydrophones, seismometers, and an ionospheric radio sounding system, the researchers investigated the connection between waves in these three areas. We expanded on a previous theoretical model (also suggested by us), confirming that ocean tides are the main energy source for these interactions. The study found that the ice shelf picks up more tidal harmonics than a nearby seafloor sensor, what supports the idea of resonance-related amplification. Notably, some vibrations in the ice shelf have different periods than normal tidal movements, which could be due to the RIS resonances. These resonances might play a role in maintaining the overall wave activity in the atmosphere and ocean. The research showed a significant correlation between the ice shelf's vertical movements and the atmospheric waves.

The researchers have developed a mathematical model to understand how these atmospheric waves, called acoustic-gravity waves (AGWs), are created by the vibrations of ice shelves. The model is based on a method previously used in seismology and underwater acoustics and accounts for various factors that affect the waves, such as the properties of the source, the way the waves bend and spread due to wind, and how they dissipate. The researchers applied this model to study the atmospheric waves generated by vibrations of the Ross Ice Shelf in Antarctica. The results show a complex three-dimensional structure of the AGW field, highlighting the impact of different environmental factors on the wave activity. The variation in wave amplitude depends on the spectrum of ice surface vibrations and the temperature and wind conditions at different heights in the atmosphere. The study found that waves with periods of several hours can transfer energy from the ice shelf to the middle and upper atmosphere in various directions. This new approach could help scientists better understand the conditions and stability of ice shelves in the future.

Atmospheric waves are also affected by resonance properties of the atmosphere itself. Our project investigated this aspect too. To do this, the researchers used techniques that involved studying the glowing light in the sky, GPS data, and high-frequency radar. We found that various wave sources can cause the atmosphere to vibrate at specific frequencies, like how a string on a musical instrument vibrates when plucked. We used mathematical models to better understand these vibrations and how they are caused by ground-shaking events and large ocean waves. We considered two types of atmospheric vibrations: one that is related to sound waves with periods of about few minutes, and another that is connected to the atmosphere's ability to float and have periods of up to several hours. The sound-related vibrations depend on the temperature of the atmosphere and are more common in polar regions during certain times of the year. The floating-related vibrations are highly influenced by the speed and direction of the wind. These vibrations can be used to better understand the connection between the Earth's surface and its atmosphere, which can help in monitoring our environment.